Srinivasan Vedantham

Interests

Teaching

My teaching interests are to provide didactic lectures in Medical Imaging Physics for Residents and Fellows, to provide graduate education on x-ray imaging modalities including radiography, mammography, fluoroscopy, tomosynthesis and computed tomography (CT), and to provide continuing education courses through professional organizations.

Research

My research interests are in the design, development and clinical translation of novel x-ray imaging systems and imaging techniques with particular focus on oncological and interventional imaging. Along with my collaborators and colleagues, I have made contributions to breast cancer imaging including small-field digital mammography for stereotactic core-biopsies, full-field digital mammography and digital breast tomosynthesis. Currently, I am working on developing advanced tomographic techniques and systems for breast imaging and its clinical translation. This design, development and clinical translation oriented research is funded by the National Institutes of Health. I also conduct research in interventional imaging with a focus on developing advanced detector technology.

Courses

Scholarly Contributions

Chapters

• Karellas, A., Avery, R., Covington, M., Eisenbrey, J., Jokerst, C., Saranathan, M., Sharma, P., & Vedantham, S. (2022). Physics in Imaging Special Edition Module. In American College of Radiology Continuous Professional Improvement (CPI). American College of Radiology.
• Vedantham, S., Sharma, P., Saranathan, M., Covington, M. F., Eisenbrey, J. R., & Jokerst, C. E. (2022). CPI Physics in Imaging Special Edition Module. In ACR Continuous Professional Improvement. Reston, VA: American College of Radiology. doi:10.54057/cpi.ph2022
• Karellas, A., & Vedantham, S. (2020).

  Clinical Mammography Physics

  . In Clinical Imaging Physics: Current and Emerging Practice. doi:10.1002/9781118753798.ch7
• Karellas, A., & Vedantham, S. (2020). Clinical Mammography Physics: Emerging Practice. In Clinical Medical Imaging Physics: Current and Emerging Practice (E Samei, DE Pfeiffer, Eds.)(p. 107). John Wiley & Sons.
• Vedantham, S. (2018). Tissue Substitute Materials for Diagnostic X-ray Imaging. In Handbook of X-ray Imaging (Russo P, Ed.)(pp 1107-1132). Boca Raton, FL: Taylor & Francis Group, CRC Press.
• Karellas, A., & Vedantham, S. (2017). The Breast X-ray Imaging Continuum – Mammography, Digital Breast Tomosynthesis and Cone-beam Breast Computed Tomography. In Essentials: Dedicated Cone-beam Breast Computed Tomography (O’Connell AM, Ed.)(pp 9-13). Pittsford, NY: Imaging Science Today, LLC.
• Vedantham, S. (2017). Tissue Substitute Materials for Diagnostic X-ray Imaging. In Handbook of X-ray Imaging. Routledge Handbooks Online. doi:10.1201/9781351228251-56
• Vedantham, S., Karellas, A., & Vijayaraghavan, G. R. (2017). Dedicated Cone-beam Breast Computed Tomography versus. Digital Breast Tomosynthesis. In Essentials: Dedicated Cone-beam Breast Computed Tomography (O’Connell AM, Ed.)(pp 78-93). Pittsford, NY: Imaging Science Today, LLC.
• Karellas, A., & Vedantham, S. (2015). Radiologic image formation: physical principles, technology, and radiation dose considerations. In Diagnostic Imaging of Child Abuse. doi:10.1017/CBO9780511862366.040
• Vijayaraghavan, G. R., Vedantham, S., Khan, A., & Karellas, A. (2015). Molecular Basis of Breast Cancer Imaging. In Precision Molecular Pathology of Breast Cancer. Springer, New York, NY. doi:10.1007/978-1-4939-2886-6_1
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  Over the past decade, annually for women 50 years of age or older, the breast cancer incidence rate in the United States has ranged from 400 to 500 per 100 000 women and the breast cancer mortality rate has ranged from 60 to 80 per 100 000 women. Though there has been a decline in the breast cancer mortality in the past decade it continues to be the second leading cause of death after lung cancer in women over 40 years of age. Breast cancer continues to be a major health issue among women in the United States. Screening mammogram has significantly contributed to the reduction in mortality. However, screening mammogram has its own limitations. Its sensitivity is 80 % in fatty breasts but is substantially lower in dense breasts. On average nearly 30 % of women reporting for mammograms have dense breasts and 1 in 2 cancers in dense breasts are missed on mammograms due to the masking effect caused by overlapping tissues.
• Karellas, A., Vedantham, S., Whitman, G. J., & Haygood, T. M. (2009). Detectors for digital mammography. In Digital mammography: a practical approach. Cambridge University Press. doi:10.1017/CBO9781139049337.002
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  Introduction Mammography is the most technically demanding radiographic modality, requiring high spatial resolution, excellent low contrast discrimination, and wide dynamic range. The development of dedicated mammography systems [1] in the mid-1960s and the refinements in film-screen technology over its long evolution [2,3] were of critical importance in establishing the benefits of mammography in reducing breast cancer mortality [4–10]. The use of film-screen technology over 30 years ensured excellent spatial resolution under optimal conditions. The high spatial resolution requirement was thought to be essential for imaging small and subtle calcifications as small as 100–200 μm, in particular for visualizing its morphology. In spite of the excellent imaging characteristics of film-screen technology under optimal exposure and film development conditions, intrinsically images are more susceptible to artifacts. Small deviations from optimal exposure and processing conditions can have profound effects on mammographic image quality, such as its ability to provide a balanced image over regions of the breast that vary in radiographic density. The well-documented weaknesses of film-screen technology [11–13] include limited dynamic range, limited tolerance to exposure conditions, complexity and instabilities due to the chemical processing of film, and the lack of ability to digitally communicate, store, and enhance the images.

Journals/Publications

• Fu, Z., Tseng, H. W., & Vedantham, S. (2024). An attenuation field network for dedicated cone beam breast CT with short scan and offset detector geometry. Scientific reports, 14(1), 319.
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  The feasibility of full-scan, offset-detector geometry cone-beam CT has been demonstrated for several clinical applications. For full-scan acquisition with offset-detector geometry, data redundancy from complementary views can be exploited during image reconstruction. Envisioning an upright breast CT system, we propose to acquire short-scan data in conjunction with offset-detector geometry. To tackle the resulting incomplete data, we have developed a self-supervised attenuation field network (AFN). AFN leverages the inherent redundancy of cone-beam CT data through coordinate-based representation and known imaging physics. A trained AFN can query attenuation coefficients using their respective coordinates or synthesize projection data including the missing projections. The AFN was evaluated using clinical cone-beam breast CT datasets (n = 50). While conventional analytical and iterative reconstruction methods failed to reconstruct the incomplete data, AFN reconstruction was not statistically different from the reference reconstruction obtained using full-scan, full-detector data in terms of image noise, image contrast, and the full width at half maximum of calcifications. This study indicates the feasibility of a simultaneous short-scan and offset-detector geometry for dedicated breast CT imaging. The proposed AFN technique can potentially be expanded to other cone-beam CT applications.
• Nisbet, A. I., Ahmadian, D., Vedantham, S., & Chiang, J. A. (2024). An unusual artifact observed on screening mammography in a patient with an LVAD. Journal of applied clinical medical physics, e14255.
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  Screening mammography and digital breast tomosynthesis consist of high-resolution x-ray images to identify findings that are potentially indicative of breast cancer, enabling early detection and reduction of breast cancer mortality. Imaging artifacts can occasionally occur, sometimes due to patient-related medical devices. Because of continuous evolution of new technologies, there is potential for novel artifacts to be encountered. In this technical note, we report an unusual artifact in the screening mammogram of a patient with an Abbott HeartMate 3 left ventricular assist device (LVAD).
• Shazeeb, M. S., Moholkar, V., King, R. M., Vedantham, S., Vardar, Z., Kraitem, A., Lindsay, C., Anagnostakou, V., Singh, J., Massari, F., de Macedo Rodrigues, K., Naragum, V., Puri, A. S., Carniato, S., Gounis, M. J., & Kühn, A. L. (2023). Assessment of thrombectomy procedure difficulty by neurointerventionalists based on vessel geometry parameters from carotid artery 3D reconstructions. Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia, 113, 121-125.
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  Diagnosing and treating acute ischemic stroke patients within a narrow timeframe is challenging. Time needed to access the occluded vessel and initiate thrombectomy is dictated by the availability of information regarding vascular anatomy and trajectory. Absence of such information potentially impacts device selection, procedure success, and stroke outcomes. While the cervical vessels allow neurointerventionalists to navigate devices to the occlusion site, procedures are often encumbered due to tortuous pathways. The purpose of this retrospective study was to determine how neurointerventionalists consider the physical nature of carotid segments when evaluating a procedure's difficulty.
• Vedantham, S. (2023). Contrast-enhanced breast computed tomography: can lymph node metastasis be predicted from primary tumor?. European radiology.
• Vedantham, S., Shazeeb, M. S., Chiang, A., & Vijayaraghavan, G. R. (2023). Artificial Intelligence in Breast X-Ray Imaging. Seminars in ultrasound, CT, and MR, 44(1), 2-7.
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  This topical review is focused on the clinical breast x-ray imaging applications of the rapidly evolving field of artificial intelligence (AI). The range of AI applications is broad. AI can be used for breast cancer risk estimation that could allow for tailoring the screening interval and the protocol that are woman-specific and for triaging the screening exams. It also can serve as a tool to aid in the detection and diagnosis for improved sensitivity and specificity and as a tool to reduce radiologists' reading time. AI can also serve as a potential second 'reader' during screening interpretation. During the last decade, numerous studies have shown the potential of AI-assisted interpretation of mammography and to a lesser extent digital breast tomosynthesis; however, most of these studies are retrospective in nature. There is a need for prospective clinical studies to evaluate these technologies to better understand their real-world efficacy. Further, there are ethical, medicolegal, and liability concerns that need to be considered prior to the routine use of AI in the breast imaging clinic.
• Vedantham, S., Tseng, H. W., Fu, Z., & Chow, H. S. (2023). Dedicated Cone-Beam Breast CT: Reproducibility of Volumetric Glandular Fraction with Advanced Image Reconstruction Methods. Tomography (Ann Arbor, Mich.), 9(6), 2039-2051.
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  Dedicated cone-beam breast computed tomography (CBBCT) is an emerging modality and provides fully three-dimensional (3D) images of the uncompressed breast at an isotropic voxel resolution. In an effort to translate this modality to breast cancer screening, advanced image reconstruction methods are being pursued. Since radiographic breast density is an established risk factor for breast cancer and CBBCT provides volumetric data, this study investigates the reproducibility of the volumetric glandular fraction (VGF), defined as the proportion of fibroglandular tissue volume relative to the total breast volume excluding the skin. Four image reconstruction methods were investigated: the analytical Feldkamp-Davis-Kress (FDK), a compressed sensing-based fast, regularized, iterative statistical technique (FRIST), a fully supervised deep learning approach using a multi-scale residual dense network (MS-RDN), and a self-supervised approach based on Noise-to-Noise (N2N) learning. Projection datasets from 106 women who participated in a prior clinical trial were reconstructed using each of these algorithms at a fixed isotropic voxel size of (0.273 mm). Each reconstructed breast volume was segmented into skin, adipose, and fibroglandular tissues, and the VGF was computed. The VGF did not differ among the four reconstruction methods ( = 0.167), and none of the three advanced image reconstruction algorithms differed from the standard FDK reconstruction ( > 0.862). Advanced reconstruction algorithms developed for low-dose CBBCT reproduce the VGF to provide quantitative breast density, which can be used for risk estimation.
• Vijayaraghavan, G. R., Ge, C., Lee, A., Roubil, J. G., Kandil, D. H., Dinh, K. H., & Vedantham, S. (2023). Savi-Scout Radar Localization: Transitioning From the Traditional Wire Localization to Wireless Technology for Surgical Guidance at Lumpectomies. Seminars in ultrasound, CT, and MR, 44(1), 12-17.
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  Breast-conserving surgery or lumpectomy requires localization of the lesion prior to surgery, which is traditionally accomplished by imaging-guided wire localization. Over the last decade, alternatives to wire localization have emerged. This work reviews the literature on one such wireless technology, SaviScout radar (SSR) system, and shares our experience with using this technology for presurgical tumor localization. The SSR surgical guidance system is non-radioactive. The radiologist implants a reflector device in the breast under mammography or ultrasound guidance at any time prior to surgery. The placement of this reflector can be confirmed from the cadence of a handheld percutaneous probe of a handpiece and console system. Results from several studies show that the surgical outcomes from SSR and wire-localization are similar. SSR provides operational advantages as the scheduling for reflector placement by radiologists is decoupled from surgery, but at an increased cost compared to wire-localization.
• Vijayaraghavan, G. R., Guembou, I. M., & Vedantham, S. (2023). The Current State of Timeliness in the Breast Cancer Diagnosis Journey: Abnormal Screening to Biopsy. Seminars in ultrasound, CT, and MR, 44(1), 56-61.
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  There are several steps involved in a breast cancer diagnosis, starting from the initial abnormal screening mammogram. Each step from the additional imaging to a biopsy provokes anxiety. Timely attention to these appointments will not only help allay anxiety but also provide better care. While breast facilities routinely audit their performance, currently timeliness is not one of the audit parameters. The role of timeliness as a robust quality tool is gaining attention. In this study, we review the timeline of care at our facility over a 1-year period (October 2021- September 2022) and compare them with those reported by National Quality Measures for Breast Centers (NQMBC). Race, ethnicity, location, and type of facility affect the outcome of care and contribute to delays in providing care. In this manuscript, we outline some of the major factors. Societal guidelines outlining some metrics for timeliness may be a useful first step.
• Vijayargahavan, G. R., Watkins, J., Tyminski, M., Venkataraman, S., Amornsiripanitch, N., Newburg, A., Ghosh, E., & Vedantham, S. (2023). Audit of Prior Screening Mammograms of Screen-Detected Cancers: Implications for the Delay in Breast Cancer Detection. Seminars in ultrasound, CT, and MR, 44(1), 62-69.
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  When cancer is detected in a screening mammogram, on occasion retrospective review of prior screening (pre-index) mammograms indicates a likely presence of cancer. These missed cancers during pre-index screens constitute a delay in detection and diagnosis. This study was undertaken to quantify the missed cancer rate by auditing pre-index screens to improve the quality of mammography screening practice. From a cohort of 135 screen-detected cancers, 120 pre-index screening mammograms could be retrieved and served as the study sample. A consensus read by 2 radiologists who interpreted the pre-index screens in an unblinded manner with full knowledge of cancer location, cancer type, lesion type, and pathology served as the truth or reference standard. Five radiologists interpreted the pre-index screens in a blinded manner. Established performance metrics such as sensitivity and specificity were quantified for each reader in interpreting these pre-index screens in a blinded manner. All five radiologists detected lesions in 8/120 (6.7%) screens. Excluding the 2 readers whose performance was close to random, all the 3 remaining readers detected lesions in 13 pre-index screens. This indicates that there is a delay in diagnosis by at least one cycle from 8/120 (6.7%) to 13/120 (10.8%). There were no observable trends in terms of either the cancer type or the lesion type. Auditing prior screening mammograms in screen-detected cancers can help in identifying the proportion of cases that were missed during interpretation and help in quantifying the delay in breast cancer detection.
• Bilgin, A., Karellas, A., Vedantham, S., Tseng, H. W., & Fu, Z. (2020). A Multi-Slice Residual Dense Network Assisted Sparse-view Reconstruction for Breast Computed Tomography. Scientific Reports.
• Chen, J. Y., Vedantham, S., & Lexa, F. J. (2022). Burnout and work-work imbalance in radiology- wicked problems on a global scale. A baseline pre-COVID-19 survey of US neuroradiologists compared to international radiologists and adjacent staff. European journal of radiology, 110153.
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  Worldwide, radiologists are experiencing increasing clinical workloads with associated increased burnout. This paper will review burnout definitions, prevalence, and causes. We will also share data from a survey of US neuroradiologists as an example of the impact of work-work imbalances from clinical overload. This article examines the impact on several key job indicators and upon the quality of the neuroradiology work environment in one nation. Finally, we will review proposals for ameliorating and preventing radiologist burnout.
• Di Maria, S., Vedantham, S., & Vaz, P. (2022). Breast dosimetry in alternative X-ray-based imaging modalities used in current clinical practices. European journal of radiology, 155, 110509.
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  In X-ray breast imaging, Digital Mammography (DM) and Digital Breast Tomosynthesis (DBT), are the standard and largely used techniques, both for diagnostic and screening purposes. Other techniques, such as dedicated Breast Computed Tomography (BCT) and Contrast Enhanced Mammography (CEM) have been developed as an alternative or a complementary technique to the established ones. The performance of these imaging techniques is being continuously assessed to improve the image quality and to reduce the radiation dose. These imaging modalities are predominantly used in the diagnostic setting to resolve incomplete or indeterminate findings detected with conventional screening examinations and could potentially be used either as an adjunct or as a primary screening tool in select populations, such as for women with dense breasts. The aim of this review is to describe the radiation dosimetry for these imaging techniques, and to compare the mean glandular dose with standard breast imaging modalities, such as DM and DBT.
• Di Maria, S., Vedantham, S., & Vaz, P. (2022). X-ray dosimetry in breast cancer screening: 2D and 3D mammography. European journal of radiology, 151, 110278.
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  According to the World Health Organization (WHO), at the end of 2020, 7.8 million women alive were diagnosed with breast cancer in the past 5 years, making it the world's most prevalent cancer. It is largely recognized and demonstrated that early detection represents the first strategy to follow in the fight against cancer. The effectiveness of mammography screening for early breast cancer detection has been proven in several surveys and studies over the last three decades. The estimation of the Mean Glandular Dose (MGD) is important to understand the radiation-associated risk from breast x-ray imaging exams. It continues to be the subject of numerous studies and debates, since its accuracy is directly related to risk estimation and for optimizing breast cancer screening programs. This manuscript reviews the main dosimetry formalisms used to estimate the MGD in mammography and to understand the continuing efforts to reduce the absorbed dose over the last forty years. The dosimetry protocols were formulated initially for mammography. Digital breast tomosynthesis (DBT) either in conjunction with synthesized digital mammogram (SDM) or with digital mammography (DM), is routinely used in many breast cancer screening programs and consequently the dosimetry protocols were extended for these techniques.
• Roychowdhury, P., Vijayaraghavan, G. R., Roubil, J., Williams, I. M., Siddiqui, E., & Vedantham, S. (2022). Value of BI-RADS 3 Audits. Biomedical journal of scientific & technical research, 41(5), 33086-33092.
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  BI-RADS 3 is an established assessment category in which the probability of malignancy is equal to or less than 2%. However, monitoring adherence to imaging criteria can be challenging and there are few established benchmarks for auditing BI-RADS 3 assignments. In this study, we explore some parameters that could serve as useful tools for quality control and clinical practice management.
• Tseng, H. W., Karellas, A., & Vedantham, S. (2022). Dedicated cone-beam breast CT: Data acquisition strategies based on projection angle-dependent normalized glandular dose coefficients. Medical physics.
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  Dedicated cone-beam breast computed tomography (CBBCT) using short-scan acquisition is being actively investigated to potentially reduce the radiation dose to the breast. This would require determining the optimal x-ray source trajectory for such short-scan acquisition.
• Vedantham, S., & Karellas, A. (2022). Breast Cancer Screening: Opportunities and Challenges with Fully 3D Tomographic X-Ray Imaging. Bridge (National Academy of Engineering, Washington, D.C. : 1969), 52(1), 33-42.
• Vedantham, S., Karellas, A., & Tseng, H. W. (2022). Dedicated cone‐beam breast CT: Data acquisition strategies based on projection angle‐dependent normalized glandular dose coefficients. Medical Physics. doi:10.1002/mp.16129
• Vedantham, S., Siddiqui, E., Williams, I. M., Roubil, J., Vijayaraghavan, G. R., & Roychowdhury, P. (2022). Value of BI-RADS 3 Audits. Biomedical Journal of Scientific and Technical Research, 41(5), 33086-33092. doi:10.26717/bjstr.2022.41.006668
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  BI-RADS 3 is an established assessment category in which the probability of malignancy is equal to or less than 2%. However, monitoring adherence to imaging criteria can be challenging and there are few established benchmarks for auditing BI-RADS 3 assignments. In this study, we explore some parameters that could serve as useful tools for quality control and clinical practice management.This retrospective study covered a 4-year period (Jan 2014-Dec 2017) and included all women over 40 years who were recalled from a screening exam and had an initial assignment of BI-RADS 3 (probably benign) category after diagnostic workup. A follow-up period of 2 years following the assignment of BI-RADS 3 was used for quantitative quality control metrics.Among 135,765 screening exams, 13,453 were recalled and 1,037 BI-RADS 3 cases met inclusion criteria. The follow-up rate at 24 months was 86.7%. The upgrade rate was 7.4% (77/1,037) [CI: 5.9-9.2%] and the PPV3 was 33.8% (26/77) [CI: 23.4-45.5%]. The cancer yield was 2.51% (26/1,037) [CI: 1.64-3.65%] and did not differ (p=0. 243) from the 2% probability of malignancy. The initial BI-RADS3 per screening exam and per recall from screening were 0.76% (1,037/135,765) [CI: 0.72-0.81%] and 7.7% (1,037/13,453) [CI: 7.26-8.17%], respectively.Regular audit of BIRADS 3 metrics has the potential to provide additional insights for clinical practice management. Data from varied clinical settings with input from an expert committee could help establish benchmarks for these metrics.
• Li, Z., Fu, Z., Keerthivasan, M., Bilgin, A., Johnson, K., Galons, J. P., Vedantham, S., Martin, D. R., & Altbach, M. I. (2021). Rapid high-resolution volumetric T1 mapping using a highly accelerated stack-of-stars Look Locker technique. Magnetic resonance imaging, 79, 28-37.
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  To develop a fast volumetric T mapping technique.
• Sawyer, D. M., Mushtaq, R., Vedantham, S., Shareef, F., Desoky, S. M., Arif-Tiwari, H., Gilbertson-Dahdal, D. L., & Udayasankar, U. K. (2021). Performance of overnight on-call radiology residents in interpreting unenhanced abdominopelvic magnetic resonance imaging studies performed for pediatric right lower quadrant abdominal pain. Pediatric radiology, 51(8), 1378-1385.
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  Abdominopelvic magnetic resonance imaging (MRI) is increasingly being used to evaluate children with abdominal pain suspected of having acute appendicitis. At our institution, these examinations are preliminarily interpreted by radiology residents, especially when performed after hours.
• Tseng, H. W., Karellas, A., & Vedantham, S. (2021). Radiation dosimetry of a clinical prototype dedicated cone-beam breast CT system with offset detector. Medical physics.
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  A clinical-prototype, dedicated, cone-beam breast computed tomography (CBBCT) system with offset detector is undergoing clinical evaluation at our institution. This study is to estimate the normalized glandular dose coefficients ( ) that provide air kerma-to-mean glandular dose conversion factors using Monte Carlo simulations.
• Vedantham, S., Karellas, A., & Tseng, H. W. (2021). Radiation dosimetry of a clinical prototype dedicated cone‐beam breast CT system with offset detector. Medical Physics, 48(3), 1079-1088. doi:10.1002/mp.14688
• Vedantham, S., Vijayaraghavan, G. R., Kona, M., Maheswaran, A., Kandil, D. H., & Toke, M. K. (2021). Ultrasound Imaging Morphology is Associated with Biological Behavior in Invasive Ductal Carcinoma of the Breast. Journal of Clinical Imaging Science, 11, 48. doi:10.25259/jcis_60_2021
• Vijayaraghavan, G. R., Kona, M., Maheswaran, A., Kandil, D. H., Toke, M. K., & Vedantham, S. (2021). Ultrasound Imaging Morphology is Associated with Biological Behavior in Invasive Ductal Carcinoma of the Breast. Journal of clinical imaging science, 11, 48.
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  Ultrasound (US) is commonly used for diagnostic evaluation of breast lesions. The objective of this study was to investigate the association between US imaging morphology from routine radiologists' interpretation and biological behavior such as receptor status and tumor grade determined from histopathology in invasive ductal carcinoma (IDC).
• Fu, Z., Tseng, H. W., Vedantham, S., Karellas, A., & Bilgin, A. (2020). A residual dense network assisted sparse view reconstruction for breast computed tomography. Nature Scientific reports, 10(1), 21111.
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  To develop and investigate a deep learning approach that uses sparse-view acquisition in dedicated breast computed tomography for radiation dose reduction, we propose a framework that combines 3D sparse-view cone-beam acquisition with a multi-slice residual dense network (MS-RDN) reconstruction. Projection datasets (300 views, full-scan) from 34 women were reconstructed using the FDK algorithm and served as reference. Sparse-view (100 views, full-scan) projection data were reconstructed using the FDK algorithm. The proposed MS-RDN uses the sparse-view and reference FDK reconstructions as input and label, respectively. Our MS-RDN evaluated with respect to fully sampled FDK reference yields superior performance, quantitatively and visually, compared to conventional compressed sensing methods and state-of-the-art deep learning based methods. The proposed deep learning driven framework can potentially enable low dose breast CT imaging.
• Karellas, A., Vedantham, S., Tseng, H., Konate, S., & Shi, L. (2020). Dedicated cone-beam breast CT using laterally-shifted detector geometry: Quantitative analysis of feasibility for clinical translation. Journal of X-Ray Science and Technology, 28(3), 405-426. doi:10.3233/xst-200651
• Kotecha, H. M., Lo, H. S., Vedantham, S., Shin, H., & Cerniglia, C. A. (2020). Abbreviated MRI of the foot in patients with suspected osteomyelitis. Emergency radiology, 27(1), 9-16. doi:10.1007/s10140-019-01722-y
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  To determine the diagnostic accuracy of an abbreviated magnetic resonance imaging (MRI) protocol of the foot for the diagnosis of osteomyelitis in patients with acute foot infection.
• Liau, J., Vedantham, S., Babiker, H. M., McGlothin, T., & Martin, D. R. (2020). Quantitative metric for assessment of pancreatic ductal adenocarcinoma treatment response in T1-weighted gadolinium-enhanced magnetic resonance imaging. Annals of pancreatic cancer, 3.
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  We theoretically derived a new quantitative metric reflecting the product of T1 signal intensity and contrast media concentration () using first principles for the signal provided by the gradient echo sequence. This metric can be used with conventional gadolinium contrast-enhanced magnetic resonance imaging (CE-MRI) exams. We used this metric to test our hypothesis that gadolinium enhancement changes with pancreatic ductal adenocarcinoma (PDA) treatment response, and that this metric may differentiate responders from non-responders.
• Tseng, H. W., Vedantham, S., & Karellas, A. (2020). Cone-beam breast computed tomography using ultra-fast image reconstruction with constrained, total-variation minimization for suppression of artifacts. Physica Medica, 73, 117-124.
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  Compressed sensing based iterative reconstruction algorithms for computed tomography such as adaptive steepest descent-projection on convex sets (ASD-POCS) are attractive due to their applicability in incomplete datasets such as sparse-view data and can reduce radiation dose to the patients while preserving image quality. Although IR algorithms reduce image noise compared to analytical Feldkamp-Davis-Kress (FDK) algorithm, they may generate artifacts, particularly along the periphery of the object. One popular solution is to use finer image-grid followed by down-sampling. This approach is computationally intensive but may be compensated by reducing the field of view. Our proposed solution is to replace the algebraic reconstruction technique within the original ASD-POCS by ordered subsets-simultaneous algebraic reconstruction technique (OS-SART) and with initialization using FDK image. We refer to this method as Fast, Iterative, TV-Regularized, Statistical reconstruction Technique (FIRST). In this study, we investigate FIRST for cone-beam dedicated breast CT with large image matrix. The signal-difference to noise ratio (SDNR), the difference of the mean value and the variance of adipose and fibroglandular tissues for both FDK and FIRST reconstructions were determined. With FDK serving as the reference, the root-mean-square error (RMSE), bias, and the full-width at half-maximum (FWHM) of microcalcifications in two orthogonal directions were also computed. Our results suggest that FIRST is competitive to the finer image-grid method with shorter reconstruction time. Images reconstructed using the FIRST do not exhibit artifacts and outperformed FDK in terms of image noise. This suggests the potential of this approach for radiation dose reduction in cone-beam breast CT.
• Tseng, H. W., Vedantham, S., Cho, S. H., & Karellas, A. (2020). Joint optimization of collimator and reconstruction parameters in x-ray fluorescence computed tomography using analytical point spread function and model observer. IEEE transactions on bio-medical engineering, 67(9), 2443-2452. doi:10.1109/TBME.2019.2963040.
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  To jointly optimize collimator design and image reconstruction algorithm in X-ray Fluorescence Computed Tomography (XFCT) for imaging low concentrations of high atomic number (Z) elements in small animal models.
• Tseng, H., Karellas, A., & Vedantham, S. (2020). Sparse-view, short-scan, dedicated cone-beam breast computed tomography: image quality assessment. Biomedical Physics & Engineering Express, 6, 065015. doi:https://doi.org/10.1088/2057-1976/abb834
• Vedantham, S. (2020). White matter hyperintensities volume and cognition: Assessment of a deep learning based lesion detection and quantification algorithm on the Alzheimers Disease Neuroimaging Initiative. ArXiv Preprint.
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  The relationship between cognition and white matter hyperintensities (WMH)volumes often depends on the accuracy of the lesion segmentation algorithmused. As such, accurate detection and quantification of WMH is of greatinterest. Here, we use a deep learning-based WMH segmentation algorithm,StackGen-Net, to detect and quantify WMH on 3D FLAIR volumes from ADNI. We useda subset of subjects (n=20) and obtained manual WMH segmentations by anexperienced neuro-radiologist to demonstrate the accuracy of our algorithm. Ona larger cohort of subjects (n=290), we observed that larger WMH volumescorrelated with worse performance on executive function (P=.004), memory(P=.01), and language (P=.005).[Journal_ref: ]
• Vedantham, S., Shin, H., Lo, H. S., Kotecha, H. M., & Cerniglia, C. A. (2020). Abbreviated MRI of the foot in patients with suspected osteomyelitis.. Emergency radiology, 27(1), 9-16. doi:10.1007/s10140-019-01722-y
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  To determine the diagnostic accuracy of an abbreviated magnetic resonance imaging (MRI) protocol of the foot for the diagnosis of osteomyelitis in patients with acute foot infection..This retrospective study evaluated adult patients (age 18 and over) visiting an academic medical center from 1 January 2013 to 31 December 2015 who were imaged with MRI for suspected acute pedal osteomyelitis. Examinations were performed utilizing the departmental standard protocol. All examinations were retrospectively interpreted by five radiologists under two protocols: a reference standard protocol consisting of all non-contrast sequences obtained at initial acquisition and an abbreviated protocol consisting of only coronal T1-weighted and sagittal T2-weighted fast multiplanar inversion-recovery (FMPIR) sequences. Interpretation of the two imaging subsets was separated in time by at least 6 weeks for each reader. Each examination was assigned a score to represent one of four diagnostic categories: normal; soft tissue infection without bone changes or bone changes specific to a non-infectious etiology; nonspecific bone marrow changes; or bone changes specific for osteomyelitis. Diagnostic accuracy of both protocols was determined based on clinical diagnosis and treatment of osteomyelitis, and histopathology when available..One hundred and two MRI examinations met inclusion criteria; participants ranged in age from 26 to 91 years, with a mean age of 59 years. Seventy examinations were performed for male participants (69%) and 32 for female participants (31%). Thirty-five had a confirmed diagnosis of osteomyelitis, while the remainder (n = 67) did not. An average of 6 non-contrast sequences was performed during each examination. The most common protocol (53/102 examinations) was comprised of the following 6 sequences: axial T1-weighted, axial fat-saturated proton density, sagittal T1-weighted, sagittal T2-weighted FMPIR, coronal T1-weighted, and coronal fat-saturated proton density. After patient positioning, the abbreviated protocol sequences (sagittal T2-weighted FMPIR and coronal T1-weighted) were performed in an average total of 8 min. The reference standard protocol required an average of 22 min to complete 6 sequences. Averaged across all readers, the AUC for the reference standard full protocol and the abbreviated protocols were 0.843 and 0.873, respectively. The difference in AUC between protocols was not statistically significant (p = 0.1297), with the abbreviated protocol showing a non-significantly greater AUC..An abbreviated MRI protocol, including only coronal T1-weighted and sagittal T2-weighted FMPIR images, is non-inferior to standard MRI protocol for the diagnosis of acute pedal osteomyelitis. It should be considered as a diagnostic alternative for reducing imaging time and improving patient access to MRI.
• Vedantham, S., Tseng, H. W., Konate, S., Shi, L., & Karellas, A. (2020). Dedicated cone-beam breast CT using laterally-shifted detector geometry: Quantitative analysis of feasibility for clinical translation. Journal of X-ray science and technology, 28(3), 405-426.
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  High-resolution, low-noise detectors with minimal dead-space at chest-wall could improve posterior coverage and microcalcification visibility in the dedicated cone-beam breast CT (CBBCT). However, the smaller field-of-view necessitates laterally-shifted detector geometry to enable optimizing the air-gap for x-ray scatter rejection.
• Arif-Tiwari, H., Twiss, C. O., Lin, F. C., Funk, J. T., Vedantham, S., Martin, D. R., & Kalb, B. T. (2019). Improved Detection of Pelvic Organ Prolapse: Comparative Utility of Defecography Phase Sequence to Nondefecography Valsalva Maneuvers in Dynamic Pelvic Floor Magnetic Resonance Imaging. Current problems in diagnostic radiology, 48(4), 342-347. doi:10.1067/j.cpradiol.2018.08.005
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  To evaluate the utility of a defecography phase (DP) sequence in dynamic pelvic floor MRI (DPMRI), in comparison to DPMRI utilizing only non-defecography Valsalva maneuvers (VM).
• Deng, L., Yasar, S., Ahmed, M. F., Jayarathna, S., Feng, P., Wei, B., Vedantham, S., Karellas, A., & Cho, S. H. (2019). Investigation of transmission computed tomography (CT) image quality and x-ray dose achievable from an experimental dual-mode benchtop x-ray fluorescence CT and transmission CT system. Journal of X-ray science and technology, 27(3), 431-442. doi:10.3233/XST-180457
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  To investigate the image quality and x-ray dose associated with a transmission computed tomography (CT) component implemented within the same platform of an experimental benchtop x-ray fluorescence CT (XFCT) system for multimodal preclinical imaging applications.
• Karellas, A., Vedantham, S., Deng, L., Yasar, S., Ahmed, M. F., Jayarathna, S., Feng, P., Wei, B., & Cho, S. H. (2019). Investigation of transmission computed tomography (CT) image quality and x-ray dose achievable from an experimental dual-mode benchtop x-ray fluorescence CT and transmission CT system. Journal of X-Ray Science and Technology, 27(3), 431-442. doi:10.3233/xst-180457
• Li, Z., Bilgin, A., Johnson, K., Galons, J. P., Vedantham, S., Martin, D. R., & Altbach, M. I. (2019). Rapid High-Resolution T1 Mapping Using a Highly Accelerated Radial Steady-state Free-precession Technique. Journal of magnetic resonance imaging : JMRI, 49(1), 239-252. doi:10.1002/jmri.26170
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  T mapping is often used in some clinical protocols. Existing techniques are limited in slice coverage, and/or spatial-temporal resolution, or require long acquisitions. Here we present a multi-slice inversion-recovery (IR) radial steady-state free precession (radSSFP) pulse sequence combined with a principal component (PC) based reconstruction that overcomes these limitations.
• Mushtaq, R., Desoky, S. M., Morello, F., Gilbertson-Dahdal, D., Leetch, A. N., Vedantham, S., Gopalakrishnan, G., Kalb, B. T., Martin, D. R., & Udayasankar, U. (2019). First-Line Diagnostic Evaluation of Children with Suspected Acute Appendicitis using MRI. Radiology, 291(1), 170-177. doi:10.1148/radiol.2019181959
• Pollock, G. R., Twiss, C. O., Chartier, S., Vedantham, S., Funk, J., & Arif Tiwari, H. (2019). Comparison of magnetic resonance defecography grading with POP-Q staging and Baden-Walker grading in the evaluation of female pelvic organ prolapse. Abdominal radiology (New York).
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  The physical examination and pelvic imaging with MRI are often used in the pre-operative evaluation of pelvic organ prolapse. The objective of this study was to compare grading of prolapse on defecography phase of dynamic magnetic resonance imaging (dMRI) with physical examination (PE) grading using both the Pelvic Organ Prolapse Quantification (POP-Q) staging and Baden-Walker (BW) grading systems in the evaluation of pelvic organ prolapse (POP).
• Sujlana, P. S., Mahesh, M., Vedantham, S., Harvey, S. C., Mullen, L. A., & Woods, R. W. (2019). Digital breast tomosynthesis: Image acquisition principles and artifacts. Clinical imaging, 55, 188-195. doi:10.1016/j.clinimag.2018.07.013
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  Digital breast tomosynthesis (DBT) is a new technology that is being used more frequently for both breast cancer screening and diagnostic purposes and its utilization is likely to continue to increase over time. The major benefit of tomosynthesis over 2D-mammography is that it allows radiologists to view breast tissue using a three-dimensional dataset and improves diagnostic accuracy by facilitating differentiation of potentially malignant lesions from overlap of normal tissue. In addition, image processing techniques allow reconstruction of two dimensional synthesized mammograms (SM) from DBT data, which eliminates the need for acquiring two dimensional full field digital mammography (FFDM) in addition to tomosynthesis and thereby reduces the radiation dose. DBT systems incorporate a moveable x-ray tube, which moves in a prescribed way over a limited angular range to obtain three-dimensional data of patients' breasts, and utilize reconstruction algorithms. The limited angular range for DBT leads to incomplete sampling of the object, and a movable x-ray tube prolongs the imaging time, both of which make DBT and SM susceptible to artifacts. Understanding the etiology of these artifacts should help radiologists in reducing the number of artifacts and in differentiating a true finding from one related to an artifact, thus potentially decreasing recall rates and false positive rates. This is becoming especially important with increased incorporation of DBT in practices around the world. The goal of this article is to review the physics principles behind DBT systems and use these principles to explain the origin of artifacts that can limit diagnostic evaluation.
• Udayasankar, U., Martin, D. R., Kalb, B. T., Gopalakrishnan, G., Vedantham, S., Leetch, A. N., Gilbertson-Dahdal, D., Morello, F., Desoky, S. M., Mushtaq, R., Udayasankar, U., Martin, D. R., Kalb, B. T., Gopalakrishnan, G., Vedantham, S., Leetch, A. N., Gilbertson-Dahdal, D., Morello, F., Desoky, S. M., & Mushtaq, R. (2019). First-Line Diagnostic Evaluation of Children with Suspected Acute Appendicitis using Magnetic Resonance Imaging. Radiology, 291(1), 170-177. doi:10.1148/radiol.2019181959
• Vedantham, S., Vijayaraghavan, G. R., & Newburg, A. (2019). Positive Predictive Value of Tomosynthesis-guided Biopsies of Architectural Distortions Seen on Digital Breast Tomosynthesis and without an Ultrasound Correlate. Journal of Clinical Imaging Science, 9, 53. doi:10.25259/jcis_134_2019
• Vijayaraghavan, G. R., Newburg, A., & Vedantham, S. (2019). Positive Predictive Value of Tomosynthesis-guided Biopsies of Architectural Distortions Seen on Digital Breast Tomosynthesis and without an Ultrasound Correlate. Journal of clinical imaging science, 9, 53.
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  The objective of the study was to determine the positive predictive value (PPV) of architectural distortions (AD) observed on digital breast tomosynthesis (DBT) and without an ultrasound (US) correlate.
• Kalb, B. T., Martin, D. R., Vedantham, S., Funk, J., Lin, F. C., Twiss, C. O., & Arif Tiwari, H. (2018). Improved Detection of Pelvic Organ Prolapse: Comparative Utility of Defecography Phase Sequence to Nondefecography Valsalva Maneuvers in Dynamic Pelvic Floor Magnetic Resonance Imaging. Current Problems in Diagnostic Radiology.
• Karellas, A., Vedantham, S., Shi, L., & Zhu, L. (2018). The role of off-focus radiation in scatter correction for dedicated cone beam breast CT. Medical Physics, 45(1), 191-201. doi:10.1002/mp.12686
• Marosfoi, M., Clarencon, F., Langan, E. T., King, R. M., Brooks, O. W., Tamura, T., Wainwright, J. M., Gounis, M. J., Vedantham, S., & Puri, A. S. (2018). Acute thrombus formation on phosphorilcholine surface modified flow diverters. JOURNAL OF NEUROINTERVENTIONAL SURGERY, 10(4), 406-410.
• Marosfoi, M., Clarencon, F., Langan, E. T., King, R. M., Brooks, O. W., Tamura, T., Wainwright, J. M., Gounis, M. J., Vedantham, S., & Puri, A. S. (2018). Acute thrombus formation on phosphorilcholine surface modified flow diverters. Journal of neurointerventional surgery, 10(4), 406-411.
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  Thromboembolic complications remain a limitation of flow diverting stents. We hypothesize that phosphorilcholine surface modified flow diverters (Pipeline Flex with Shield Technology, sPED) would have less acute thrombus formation on the device surface compared with the classic Pipeline Embolization device (cPED).
• O'Connell, A. M., Karellas, A., Vedantham, S., & Kawakyu-O'Connor, D. T. (2018). Newer Technologies in Breast Cancer Imaging: Dedicated Cone-Beam Breast Computed Tomography. Seminars in ultrasound, CT, and MR, 39(1), 106-113.
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  Dedicated breast computed tomography (CT) is the latest in a long history of breast imaging techniques dating back to the 1960s. Breast imaging is performed both for cancer screening as well as for diagnostic evaluation of symptomatic patients. Dedicated breast CT received US Food and Drug Administration approval for diagnostic use in 2015 and is slowly gaining recognition for its value in diagnostic 3-dimensional imaging of the breast, and also for injected contrast-enhanced imaging applications. Conventional mammography has known limitations in sensitivity and specificity, especially in dense breasts. Breast tomosynthesis was US Food and Drug Administration approved in 2011 and is now widely used. Dedicated breast CT is the next technological advance, combining real 3-dimensional imaging with the ease of contrast administration. The lack of painful compression and manipulation of the breasts also makes dedicated breast CT much more acceptable for the patients.
• Shi, L., Vedantham, S., Karellas, A., & Zhu, L. (2018). The role of off-focus radiation in scatter correction for dedicated cone beam breast CT. Medical physics, 45(1), 191-201.
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  Dedicated cone beam breast CT (CBBCT) suffers from x-ray scatter contamination. We aim to identify the source of the significant difference between the scatter distributions estimated by two recent methods proposed by our group and to investigate its effect on CBBCT image quality.
• Vedantham, S., & Karellas, A. (2018). Emerging Breast Imaging Technologies on the Horizon. Seminars in ultrasound, CT, and MR, 39(1), 114-121.
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  Early detection of breast cancers by mammography in conjunction with adjuvant therapy has contributed to reduction in breast cancer mortality. Mammography remains the "gold-standard" for breast cancer screening but is limited by tissue superposition. Digital breast tomosynthesis and more recently, dedicated breast computed tomography have been developed to alleviate the tissue superposition problem. However, all of these modalities rely upon x-ray attenuation contrast to provide anatomical images, and there are ongoing efforts to develop and clinically translate alternative modalities. These emerging modalities could provide for new contrast mechanisms and may potentially improve lesion detection and diagnosis. In this article, several of these emerging modalities are discussed with a focus on technologies that have advanced to the stage of in vivo clinical evaluation.
• Vijayaraghavan, G. R., Vedantham, S., Santos-Nunez, G., & Hultman, R. (2018). Unifocal Invasive Lobular Carcinoma: Tumor Size Concordance Between Preoperative Ultrasound Imaging and Postoperative Pathology. Clinical breast cancer.
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  We systematically analyzed the extent of disease in unifocal invasive lobular carcinoma (ILC) using ultrasonography, with the histopathologic findings as the reference standard.
• Marosfoi, M., Langan, E. T., Strittmatter, L., van, d., Vedantham, S., Arends, J., Lylyk, I. R., Loganathan, S., Hendricks, G. M., Szikora, I., Puri, A. S., Wakhloo, A. K., & Gounis, M. J. (2017). In situ tissue engineering: endothelial growth patterns as a function of flow diverter design. JOURNAL OF NEUROINTERVENTIONAL SURGERY, 9(10), 994-998.
• Shi, L., Vedantham, S., Karellas, A., & Zhu, L. (2017). X-ray scatter correction for dedicated cone beam breast CT using a forward-projection model. MEDICAL PHYSICS, 44(6), 2312-2320.
• Shrestha, S., Vedantham, S., & Karellas, A. (2017). Towards standardization of x-ray beam filters in digital mammography and digital breast tomosynthesis: Monte Carlo simulations and analytical modelling. Physics in medicine and biology, 62(5), 1969-1993.
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  In digital breast tomosynthesis and digital mammography, the x-ray beam filter material and thickness vary between systems. Replacing K-edge filters with Al was investigated with the intent to reduce exposure duration and to simplify system design. Tungsten target x-ray spectra were simulated with K-edge filters (50 µm Rh; 50 µm Ag) and Al filters of varying thickness. Monte Carlo simulations were conducted to quantify the x-ray scatter from various filters alone, scatter-to-primary ratio (SPR) with compressed breasts, and to determine the radiation dose to the breast. These data were used to analytically compute the signal-difference-to-noise ratio (SDNR) at unit (1 mGy) mean glandular dose (MGD) for W/Rh and W/Ag spectra. At SDNR matched between K-edge and Al filtered spectra, the reductions in exposure duration and MGD were quantified for three strategies: (i) fixed Al thickness and matched tube potential in kilovolts (kV); (ii) fixed Al thickness and varying the kV to match the half-value layer (HVL) between Al and K-edge filtered spectra; and, (iii) matched kV and varying the Al thickness to match the HVL between Al and K-edge filtered spectra. Monte Carlo simulations indicate that the SPR with and without the breast were not different between Al and K-edge filters. Modelling for fixed Al thickness (700 µm) and kV matched to K-edge filtered spectra, identical SDNR was achieved with 37-57% reduction in exposure duration and with 2-20% reduction in MGD, depending on breast thickness. Modelling for fixed Al thickness (700 µm) and HVL matched by increasing the kV over (0,4) range, identical SDNR was achieved with 62-65% decrease in exposure duration and with 2-24% reduction in MGD, depending on breast thickness. For kV and HVL matched to K-edge filtered spectra by varying Al filter thickness over (700, 880) µm range, identical SDNR was achieved with 23-56% reduction in exposure duration and 2-20% reduction in MGD, depending on breast thickness. These simulations indicate that increased fluence with Al filter of fixed or variable thickness substantially decreases exposure duration while providing for similar image quality with moderate reduction in MGD.
• Taschner, C. A., Vedantham, S., de, V. J., Biondi, A., Boogaarts, J., Sakai, N., Lylyk, P., Szikora, I., Meckel, S., Urbach, H., Kan, P., Siekmann, R., Bernardy, J., Gounis, M. J., & Wakhloo, A. K. (2017). Surpass Flow Diverter for Treatment of Posterior Circulation Aneurysms. AMERICAN JOURNAL OF NEURORADIOLOGY, 38(3), 582-589.
• Ulano, A. C., Vedantham, S., & Takhtani, D. (2017). Revisiting the indirect signs of a temporal bone fracture: air, air, everywhere. Emergency radiology, 24(5), 497-503.
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  The standard head CT protocol makes detection of a temporal bone fracture difficult. The purposes of our study are to revisit the finding of air in various locations around the temporal bone as an indirect sign of fracture and determine if findings could predict fracture pattern.
• Vijayaraghavan, G. R., Vedantham, S., Kataoka, M., DeBenedectis, C., & Quinlan, R. M. (2017). The Relevance of Ultrasound Imaging of Suspicious Axillary Lymph Nodes and Fine-needle Aspiration Biopsy in the Post-ACOSOG Z11 Era in Early Breast Cancer. ACADEMIC RADIOLOGY, 24(3), 308-315.
• van, d., Vedantham, S., van, d., Howk, M., Narain, T., Ty, K., Karellas, A., Gounis, M. J., Puri, A. S., & Wakhloo, A. K. (2017). Reduced Patient Radiation Exposure during Neurodiagnostic and Interventional X-Ray Angiography with a New Imaging Platform. AMERICAN JOURNAL OF NEURORADIOLOGY, 38(3), 442-449.
• Karam, A. R., Zacharias, I., Vedantham, S., Shrestha, S., Rupawala, A. H., Patel, K., Marya, N. B., Karellas, A., & Aldrugh, S. (2016). Tu1700 Radiomics of Computed Tomography (CT) Liver Scans: A Novel Method to Evaluate Liver Cirrhosis and Steatosis. Gastroenterology, 150(4), S1166-S1167. doi:10.1016/s0016-5085(16)33941-5
• Michaelsen, K. E., Krishnaswamy, V., Shi, L., Vedantham, S., Karellas, A., Pogue, B. W., Paulsen, K. D., & Poplack, S. P. (2016). Effects of breast density and compression on normal breast tissue hemodynamics through breast tomosynthesis guided near-infrared spectral tomography. Journal of biomedical optics, 21(9), 91316.
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  Optically derived tissue properties across a range of breast densities and the effects of breast compression on estimates of hemoglobin, oxygen metabolism, and water and lipid concentrations were obtained from a coregistered imaging system that integrates near-infrared spectral tomography (NIRST) with digital breast tomosynthesis (DBT). Image data were analyzed from 27 women who underwent four IRB approved NIRST/DBT exams that included fully and mildly compressed breast acquisitions in two projections—craniocaudal (CC) and mediolateral-oblique (MLO)—and generated four data sets per patient (full and moderate compression in CC and MLO views). Breast density was correlated with HbT (r=0.64, p=0.001), water (r=0.62, p=0.003), and lipid concentrations (r=?0.74, p
• Shi, L., Vedantham, S., Karellas, A., & Zhu, L. (2016). Library based x-ray scatter correction for dedicated cone beam breast CT. MEDICAL PHYSICS, 43(8), 4529-4544.
• Vedantham, S. (2016). WE-FG-207A-01: Introduction to Dedicated Breast CT - Early Studies. Medical Physics, 43(6), 3829-3830. doi:10.1118/1.4957926
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  Mammography-based screening has been a valuable imaging tool for the early detection of non-palpable lesions and has contributed to significant reduction in breast cancer associated mortality. However, the breast imaging community recognizes that mammography is not ideal, and in particular is inferior for women with dense breasts. Also, the 2-D projection of a 3-D organ results in tissue superposition contributing to false-positives. The sensitivity of mammography is breast-density dependent. Its sensitivity, especially in dense breasts, is low due to overlapping tissue and the fact that normal breast tissue, benign lesions and breast cancers all have similar “densities”, making lesion detection more difficult. We ideally need 3-D imaging for imaging the 3-D breast. MRI is 3-D, whole breast ultrasound is 3-D, digital breast tomosynthesis is called 3-D but is really “pseudo 3-D” due to poor resolution along the depth-direction. Also, and importantly, we need to be able to administer intravenous contrast agents for optimal imaging, similar to other organ systems in the body. Dedicated breast CT allows for 3-D imaging of the uncompressed breast. In current designs, the patient is positioned prone on the table and the breast is pendant through an aperture and the scan takes approximately 10 seconds [O'Connell et al., AJR 195: 496–509, 2010]. Almost on the heels of the invention of CT itself, work began on the development of dedicated breast CT. These early breast CT systems were used in clinical trials and the results from comparative performance evaluation of breast CT and mammography for 1625 subjects were reported in 1980 [Chang et al., Cancer 46: 939–46, 1980]. However, the technological limitations at that time stymied clinical translation for decades. Subsequent to the landmark article in 2001 [Boone et al., Radiology 221: 657–67, 2001] that demonstrated the potential feasibility in terms of radiation dose, multiple research groups are actively investigating dedicated breast CT. The development of large-area flat-panel detectors with field-of-view sufficient to image the entire breast in each projection enabled development of flat-panel cone-beam breast CT. More recently, the availability of complimentary metal-oxide semiconductor (CMOS) detectors with lower system noise and finer pixel pitch, combined with the development of x-ray tubes with focal spot dimensions similar to mammography systems, has shown improved spatial resolution and could improve visualization of microcalcifications. These technological developments promise clinical translation of low-dose cone-beam breast CT. Dedicated photon-counting breast CT (pcBCT) systems represent a novel detector design, which provide high spatial resolution (∼ 100µm) and low mean glandular dose (MGD). The CdTe-based direct conversion detector technology was previously evaluated and confirmed by simulations and basic experiments on laboratory setups [Kalender et al., Eur Radiol 22: 1–8, 2012]. Measurements of dose, technical image quality parameters, and surgical specimens on a pcBCT scanner have been completed. Comparative evaluation of surgical specimens showed that pcBCT outperformed mammography and digital breast tomosynthesis with respect to 3D spatial resolution, detectability of calcifications, and soft tissue delineation. Major barriers to widespread clinical use of BCT relate to radiation dose, imaging of microcalcifications, and adequate coverage of breast tissue near the chest wall. Adequate chest wall coverage is also technically challenging but recent progress in x-ray tube, detector and table design now enables full breast coverage in the majority of patients. At this time, BCT has been deemed to be suitable for diagnostic imaging but not yet for screening. The mean glandular dose (MGD) from BCT has been reported to be between 5.7 to 27.8 mGy, and this range is comparable to, and within the range of, the MGD of 2.6 to 31.6 mGy in diagnostic mammography. In diagnostic studies, the median MGD from BCT and mammography were 12.6 and 11.1 mGy, respectively [Vedantham et al., Phys Med Biol. 58: 7921–36, 2013]. Moreover, in diagnostic imaging of the breast the location of the lesion is known and therefore characterization and not detection is by far the primary consideration. The role of bCT is particularly compelling for diagnostic imaging of the breast because it may replace in part the multiple mammographic views of the breast under vigorous compression. Other non-screening potential applications of bCT include the assessment of response to neoadjuvant therapy [Vedantham et al., J Clin Imaging Sci 4, 64, 2014] and pre-surgical evaluation. Learning Objectives: 1.To understand the metrics used to evaluate screening and diagnostic imaging 2.To understand the benefits and limitations of current clinical modalities 3.To understand how breast CT can improve over current clinical modalities 4.To note the early attempts to translate breast CT to the clinic in 1970s-1990s 5.To understand the recent developments in low-dose cone-beam breast CT 6.To understand the recent developments in photon-counting breast CT 7.To understand the radiation dose, clinical translation, and recent developments in diagnostic imaging with breast CT Supported in part by NIH grants R21 CA134128, R01 CA128906 and R01 CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or the NCI.; S. Vedantham, Funding sources: Supported in part by NIH/NCI grants R01 CA128906 and R01 CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH/NCI. Disclosures: Research collaboration with Koning Corporation, West Henrietta, NY. Conflicts of Interest: J. Boone, This research was supported in part by NIH grant R01CA181081; W. Kalender, WK is founder and CEO of CT Imaging GmbH Erlangen, Germany.; A. Karellas, NIH R21 CA134128, R01 CA128906, and R01 CA195512 and Research collaboration with Koning Corporation.
• Vedantham, S., & Molloi, S. (2016). WE‐FG‐207A‐00: Advances in Dedicated Breast CT. Medical Physics, 43(6), 3829-3830. doi:10.1118/1.4957925
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  Mammography-based screening has been a valuable imaging tool for the early detection of non-palpable lesions and has contributed to significant reduction in breast cancer associated mortality. However, the breast imaging community recognizes that mammography is not ideal, and in particular is inferior for women with dense breasts. Also, the 2-D projection of a 3-D organ results in tissue superposition contributing to false-positives. The sensitivity of mammography is breast-density dependent. Its sensitivity, especially in dense breasts, is low due to overlapping tissue and the fact that normal breast tissue, benign lesions and breast cancers all have similar “densities”, making lesion detection more difficult. We ideally need 3-D imaging for imaging the 3-D breast. MRI is 3-D, whole breast ultrasound is 3-D, digital breast tomosynthesis is called 3-D but is really “pseudo 3-D” due to poor resolution along the depth-direction. Also, and importantly, we need to be able to administer intravenous contrast agents for optimal imaging, similar to other organ systems in the body. Dedicated breast CT allows for 3-D imaging of the uncompressed breast. In current designs, the patient is positioned prone on the table and the breast is pendant through an aperture and the scan takes approximately 10 seconds [O’Connell et al., AJR 195: 496–509, 2010]. Almost on the heels of the invention of CT itself, work began on the development of dedicated breast CT. These early breast CT systems were used in clinical trials and the results from comparative performance evaluation of breast CT and mammography for 1625 subjects were reported in 1980 [Chang et al., Cancer 46: 939–46, 1980]. However, the technological limitations at that time stymied clinical translation for decades. Subsequent to the landmark article in 2001 [Boone et al., Radiology 221: 657–67, 2001] that demonstrated the potential feasibility in terms of radiation dose, multiple research groups are actively investigating dedicated breast CT. The development of large-area flat-panel detectors with field-of-view sufficient to image the entire breast in each projection enabled development of flat-panel cone-beam breast CT. More recently, the availability of complimentary metal-oxide semiconductor (CMOS) detectors with lower system noise and finer pixel pitch, combined with the development of x-ray tubes with focal spot dimensions similar to mammography systems, has shown improved spatial resolution and could improve visualization of microcalcifications. These technological developments promise clinical translation of low-dose cone-beam breast CT. Dedicated photon-counting breast CT (pcBCT) systems represent a novel detector design, which provide high spatial resolution (∼ 100µm) and low mean glandular dose (MGD). The CdTe-based direct conversion detector technology was previously evaluated and confirmed by simulations and basic experiments on laboratory setups [Kalender et al., Eur Radiol 22: 1–8, 2012]. Measurements of dose, technical image quality parameters, and surgical specimens on a pcBCT scanner have been completed. Comparative evaluation of surgical specimens showed that pcBCT outperformed mammography and digital breast tomosynthesis with respect to 3D spatial resolution, detectability of calcifications, and soft tissue delineation. Major barriers to widespread clinical use of BCT relate to radiation dose, imaging of microcalcifications, and adequate coverage of breast tissue near the chest wall. Adequate chest wall coverage is also technically challenging but recent progress in x-ray tube, detector and table design now enables full breast coverage in the majority of patients. At this time, BCT has been deemed to be suitable for diagnostic imaging but not yet for screening. The mean glandular dose (MGD) from BCT has been reported to be between 5.7 to 27.8 mGy, and this range is comparable to, and within the range of, the MGD of 2.6 to 31.6 mGy in diagnostic mammography. In diagnostic studies, the median MGD from BCT and mammography were 12.6 and 11.1 mGy, respectively [Vedantham et al., Phys Med Biol. 58: 7921–36, 2013]. Moreover, in diagnostic imaging of the breast the location of the lesion is known and therefore characterization and not detection is by far the primary consideration. The role of bCT is particularly compelling for diagnostic imaging of the breast because it may replace in part the multiple mammographic views of the breast under vigorous compression. Other non-screening potential applications of bCT include the assessment of response to neoadjuvant therapy [Vedantham et al., J Clin Imaging Sci 4, 64, 2014] and pre-surgical evaluation. Learning Objectives: 1. To understand the metrics used to evaluate screening and diagnostic imaging 2. To understand the benefits and limitations of current clinical modalities 3. To understand how breast CT can improve over current clinical modalities 4. To note the early attempts to translate breast CT to the clinic in 1970s-1990s 5. To understand the recent developments in low-dose cone-beam breast CT 6. To understand the recent developments in photon-counting breast CT 7. To understand the radiation dose, clinical translation, and recent developments in diagnostic imaging with breast CT Supported in part by NIH grants R21 CA134128, R01 CA128906 and R01 CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or the NCI.; S. Vedantham, Funding sources: Supported in part by NIH/NCI grants R01 CA128906 and R01 CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH/NCI. Disclosures: Research collaboration with Koning Corporation, West Henrietta, NY. Conflicts of Interest: J. Boone, This research was supported in part by NIH grant R01CA181081; W. Kalender, WK is founder and CEO of CT Imaging GmbH Erlangen, Germany.; A. Karellas, NIH R21 CA134128, R01 CA128906, and R01 CA195512 and Research collaboration with Koning Corporation.
• Vedantham, S., Shrestha, S., & Karellas, A. (2016). MO-FG-CAMPUS-IeP1-01: Alternative K-Edge Filters for Low-Energy Image Acquisition in Contrast Enhanced Spectral Mammography. Medical Physics, 43(6), 3716-3716. doi:10.1118/1.4957333
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  Purpose: In Contrast Enhanced Spectral Mammography (CESM), Rh filter is often used during low-energy image acquisition. The potential for using Ag, In and Sn filters, which exhibit K-edge closer to, and just below that of Iodine, instead of the Rh filter, was investigated for the low-energy image acquisition. Methods: Analytical computations of the half-value thickness (HVT) and the photon fluence per mAs (photons/mm2/mAs) for 50µm Rh were compared with other potential K-edge filters (Ag, In and Sn), all with K-absorption edge below that of Iodine. Two strategies were investigated: fixed kVp and filter thickness (50µm for all filters) resulting in HVT variation, and fixed kVp and HVT resulting in variation in Ag, In and Sn thickness. Monte Carlo simulations (GEANT4) were conducted to determine if the scatter-to-primary ratio (SPR) and the point spread function of scatter (scatter PSF) differed between Rh and other K-edge filters. Results: Ag, In and Sn filters (50µm thick) increased photon fluence/mAs by 1.3–1.4, 1.8–2, and 1.7–2 at 28-32 kVp compared to 50µm Rh, which could decrease exposure time. Additionally, the fraction of spectra closer to and just below Iodine's K-edge increased with these filters, which could improve post-subtraction image contrast. For HVT matched to 50µm Rh filtered spectra, the thickness range for Ag, In, and Sn were (41,44)µm, (49,55)µm and (45,53)µm, and increased photon fluence/mAs by 1.5–1.7, 1.6–2, and 1.6–2.2, respectively. Monte Carlo simulations showed that neither the SPR nor the scatter PSF of Ag, In and Sn differed from Rh, indicating no additional detriment due to x-ray scatter. Conclusion: The use of Ag, In and Sn filters for low-energy image acquisition in CESM is potentially feasible and could decrease exposure time and may improve post-subtraction image contrast. Effect of these filters on radiation dose, contrast, noise and associated metrics are being investigated. Funding Support: Supported in part by NIH R01CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or NCI.
• Vedantham, S., Shrestha, S., & Karellas, A. (2016). WE-DE-207B-08: Towards Standardization of X-Ray Filters in Digital Mammography-Enabled Breast Tomosynthesis Systems. Medical Physics, 43(6), 3819-3819. doi:10.1118/1.4957868
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  Purpose: In digital breast tomosynthesis (DBT) systems capable of digital mammography (DM), Al filters are used during DBT and K-edge filters during DM. The potential for standardizing the x-ray filters with Al, instead of K-edge filters, was investigated with intent to reduce exposure duration and to promote a simpler system design. Methods: Analytical computations of the half-value thickness (HVT) and the photon fluence per mAs (photons/mm2/mAs) for K-edge filters (50µm Rh; 50µm Ag) were compared with Al filters of varying thickness. Two strategies for matching the HVT from K-edge and Al filtered spectra were investigated: varying the kVp for fixed Al thickness, or varying the Al thickness at matched kVp. For both strategies, Al filters were an order of magnitude thicker than K-edge filters. Hence, Monte Carlo simulations were conducted with the GEANT4 toolkit to determine if the scatter-to-primary ratio (SPR) and the point spread function of scatter (scatter PSF) differed between Al and K-edge filters. Results: Results show the potential for replacing currently used Kedge filters with Al. For fixed Al thickness (700µm), ±1 kVp and +(1–3) kVp change, matched HVT of Rh and Ag filtered spectra. At matched kVp, Al thickness range (650,750)µm and (750,860)µm matched the HVT from Rh and Ag filtered spectra. Photon fluence/mAs with Al filters were 1.5–2.5 times higher, depending on kVp and Al thickness, compared to K-edge filters. Although Al thickness was an order higher than K-edge filters, neither the SPR nor the scatter PSF differed from K-edge filters. Conclusion: The use of Al filters for digital mammography is potentially feasible. The increased fluence/mAs with Al could decrease exposure duration for the combined DBT+DM exam and simplify system design. Effect of x-ray spectrum change due to Al filtration on radiation dose, signal, noise, contrast and related metrics are being investigated. Funding support: Supported in part by NIH R21CA176470 and R01CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or NCI.
• Vedantham, S., Shrestha, S., Karellas, A., Shi, L., Gounis, M. J., Bellazzini, R., Spandre, G., Brez, A., & Minuti, M. (2016). Photon-counting hexagonal pixel array CdTe detector: Spatial resolution characteristics for image-guided interventional applications. MEDICAL PHYSICS, 43(5).
• Vijayaraghavan, G. R., Vedantham, S., Shrestha, S., Shi, L., & Karellas, A. (2016). SU-D-206-06: Task-Specific Optimization of Scintillator Thickness for CMOS-Detector Based Cone-Beam Breast CT. Medical Physics, 43(6), 3346-3346. doi:10.1118/1.4955660
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  Purpose: To optimize the cesium iodide (CsI:Tl) scintillator thickness in a complimentary metal-oxide semiconductor (CMOS)-based detector for use in dedicated cone-beam breast CT. Methods: The imaging task considered was the detection of a microcalcification cluster comprising six 220µm diameter calcium carbonate spheres, arranged in the form of a regular pentagon with 2 mm spacing on its sides and a central calcification, similar to that in ACR-recommended mammography accreditation phantom, at a mean glandular dose of 4.5 mGy. Generalized parallel-cascades based linear systems analysis was used to determine Fourier-domain image quality metrics in reconstructed object space, from which the detectability index inclusive of anatomical noise was determined for a non-prewhitening numerical observer. For 300 projections over 2π, magnification-associated focal-spot blur, Monte Carlo derived x-ray scatter, K-fluorescent emission and reabsorption within CsI:Tl, CsI:Tl quantum efficiency and optical blur, fiberoptic plate transmission efficiency and blur, CMOS quantum efficiency, pixel aperture function and additive noise, and filtered back-projection to isotropic 105µm voxel pitch with bilinear interpolation were modeled. Imaging geometry of a clinical prototype breast CT system, a 60 kV Cu/Al filtered x-ray spectrum from 0.3 mm focal spot incident on a 14 cm diameter semi-ellipsoidal breast were used to determine the detectability index for 300–600 µm thick (75µm increments) CsI:Tl. The CsI:Tl thickness that maximized the detectability index was considered optimal. Results: The limiting resolution (10% modulation transfer function, MTF) progressively decreased with increasing CsI:Tl thickness. The zero-frequency detective quantum efficiency, DQE(0), in projection space increased with increasing CsI:Tl thickness. The maximum detectability index was achieved with 525µm thick CsI:Tl scintillator. Reduced MTF at mid-to-high frequencies for 600µm thick CsI:Tl lowered the detectability index than 525µm CsI:Tl. Conclusion: For the x-ray spectrum and imaging conditions considered, a 525µm thick CsI:Tl scintillator integrated with the CMOS detector is optimal for detecting microcalcification cluster. Funding support: Supported in part by NIH R01 CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or the NCI. Disclosures: SV, GV and AK - Research collaboration, Koning Corp., West Henrietta, NY.
• Wainwright, J., Vedantham, S., Puri, A. S., Marosfoi, M. G., Langan, E. T., King, R. M., Gounis, M. J., & Clarencon, F. (2016). O-029 Acute Thrombus Formation on Flow Diverters Imaged In Vivo Using Optical Coherence Tomography. Journal of NeuroInterventional Surgery, 8(Suppl 1), A19.2-A20. doi:10.1136/neurintsurg-2016-012589.29
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  Introduction In vitro studies have shown that Pipeline Embolization Device+Shield Technology (Shield) with a surface modification of a 3 nm thick modified phosphorylcholine is less thrombogenic. 1 We hypothesize that Shield has less thrombus formation in vivo as compared to Pipeline Embolization Devices (PED) regardless of dual antiplatelet therapy (DAPT). Methods Forty rabbits with elastase induced aneurysms were randomly assigned to receive a Shield or PED. For each device, half of the animals received DAPT. In each of the four groups, 10 animals were enrolled for a period of 30 days. Herein, we report on 32 animals that have reached the study endpoint to date. Animals that received DAPT (10 mg/kg each of aspirin and clopidogrel) were started a 5 days prior to implant and continued until the endpoint at 30 days. At the time of implant optical coherence tomography (OCT, Dragonfly, St Jude) was performed before and after angioplasty, and repeated at terminal follow-up. Thrombus formation was assessed at 4 locations along the implant (distal end, at the level of the vertebral artery, at the aneurysm neck, and at the proximal end) as present or absent. Aneurysm occlusion was assessed on digital subtraction angiography after 30 days and according to the scale of Darsaut et al. 2 Results Baseline characteristics (e.g., aneurysm size, neck size, parent vessel diameter) were not different between the four groups (p > 0.1). Animals receiving DAPT had a significant reduction in PRU values (69 ± 28 vs 247 ± 41, p 0.05). The Shield was more likely to have no thrombus or thrombus only at one of the four locations as compared to PED (OR 0.10 95% CI 0.02–0.56, p = 0.01). There was no difference in thrombus at the four locations as a function of DAPT (p > 0.05). There was no dependence on aneurysm occlusion on the device used or PRU value; however, achieving complete or near complete occlusion was negatively and marginally correlated with the aneurysm neck size (Spearman’s rho = 0.314; p = 0.049). Conclusion The hypothesis that Shield technology reduces acute thrombus formation regardless of DAPT has been confirmed in vivo using OCT. References 1 G Girdhar et al . J Thromb Thrombolysis 2015; 40 :437–4432. 2 TE Darsaut, et al . AJNR . 2012; 33 :2004–2009 Disclosures M. Marosfoi: None. E. Langan: None. S. Vedantham: None. F. Clarencon: None. R. King: None. J. Wainwright: 5; C; Medtronic Neurovascular. M. Gounis: 1; C; Medtronic Neurovascular. A. Puri: 1; C; Medtronic Neurovascular. 2; C; Medtronic Neurovascular.
• Wakhoo, A. K., Vedantham, S., Uzun, O., Puri, A. S., Papa, A., Marosfoi, M. G., Langan, E. T., Korin, N., Kanapathipillai, M., Johnson, C., Ingber, D. E., Gounis, M. J., Chueh, J., Brooks, O. W., Bronstein, B. R., & Bhatta, D. (2016). Abstract WP437: Shear-activated Nanoparticle Aggregate Lysis Combined With Temporary Stent-bypass to Treat Emergent Large Vessel Occlusions (ELVO). Stroke, 47. doi:10.1161/str.47.suppl_1.wp437?cookieSet=1
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  Introduction: Despite the high effectiveness of stent-retrievers in ELVO, half of the patients remained functionally dependent (mRS≥3) after 90-days. Beyond futile recanalizations, variable endoluminal damage caused by stent-retrievers may contribute to reperfusion injury, and recruit iniflammatory cell infiltration. The goal of this study was to assess a less traumatic endovascular approach in combination with a novel shear activated-nanotherapeutic (SA-NT) that releases r-tPA when exposed to high levels of hemodynamic stress. Hypothesis: SA-NT treatment coupled with temporary endovascular bypass provides high recanalization rates while reducing vascular injury. Methods: a rabbit carotid vessel occlusion model was used. We evaluated angiographic recanalization with stent-bypass alone, intra-arterial delivery of soluble r-tPA alone, or stent-bypass combined with two doses (2 and 20 mg r-tPA) of intra-arterial infusion of either the SA-NT or soluble r-tPA. Vascular injury was compared against stent-retriever thrombectomy by assessing the level of damage on histology. Results: Shear-targeted delivery of r-tPA using the SA-NT resulted in the highest rate of complete recanalization when compared to controls (p=0.0011). SA-NT (20mg) had a higher likelihood of obtaining complete recanalization (mTICI:3) as compared to stent-bypass alone (OR: 65.019,95%CI:[1.77,>1000], p=0.0231), intra-arterial r-tPA alone (OR: 65.019, 95% CI [1.77,>1000], p=0.0231), or stent-bypass with soluble r-tPA (2 mg) (OR: 18.78, 95%CI [1.28,275.05], p=0.0322) (Figure). Histologically, there was significantly less vascular injury using a stent-bypass as compared to stent-retriever procedure (OR 12.97, 95%CI [8.01,21.02], p Conclusion: Nanoparticle-based thrombolytic therapy combined with stent-bypass achieves high rates of complete (mTICI:3) recanalization. This technology reduces vascular trauma as compared to stent-retriever thrombectomy
• Zhu, L., Vedantham, S., Shi, L., & Karellas, A. (2016). WE-DE-207B-10: Library-Based X-Ray Scatter Correction for Dedicated Cone-Beam Breast CT: Clinical Validation. Medical Physics, 43(6), 3819-3819. doi:10.1118/1.4957870
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  Purpose: Scatter contamination is detrimental to image quality in dedicated cone-beam breast CT (CBBCT), resulting in cupping artifacts and loss of contrast in reconstructed images. Such effects impede visualization of breast lesions and the quantitative accuracy. Previously, we proposed a library-based software approach to suppress scatter on CBBCT images. In this work, we quantify the efficacy and stability of this approach using datasets from 15 human subjects. Methods: A pre-computed scatter library is generated using Monte Carlo simulations for semi-ellipsoid breast models and homogeneous fibroglandular/adipose tissue mixture encompassing the range reported in literature. Projection datasets from 15 human subjects that cover 95 percentile of breast dimensions and fibroglandular volume fraction were included in the analysis. Our investigations indicate that it is sufficient to consider the breast dimensions alone and variation in fibroglandular fraction does not significantly affect the scatter-to-primary ratio. The breast diameter is measured from a first-pass reconstruction; the appropriate scatter distribution is selected from the library; and, deformed by considering the discrepancy in total projection intensity between the clinical dataset and the simulated semi-ellipsoidal breast. The deformed scatter-distribution is subtracted from the measured projections for scatter correction. Spatial non-uniformity (SNU) and contrast-to-noise ratio (CNR) were used as quantitative metrics to evaluate the results. Results: On the 15 patient cases, our method reduced the overall image spatial non-uniformity (SNU) from 7.14%±2.94% (mean ± standard deviation) to 2.47%±0.68% in coronal view and from 10.14%±4.1% to 3.02% ±1.26% in sagittal view. The average contrast to noise ratio (CNR) improved by a factor of 1.49±0.40 in coronal view and by 2.12±1.54 in sagittal view. Conclusion: We demonstrate the robustness and effectiveness of a library-based scatter correction method using patient datasets with large variability in breast dimensions and composition. The high computational efficiency and simplicity in implementation make this attractive for clinical implementation. Supported partly by NIH R21EB019597, R21CA134128 and R01CA195512.The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
• Zhu, L., Vedantham, S., Shi, L., & Karellas, A. (2016). WE-DE-207B-12: Scatter Correction for Dedicated Cone Beam Breast CT Based On a Forward Projection Model. Medical Physics, 43(6), 3820-3820. doi:10.1118/1.4957872
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  Purpose: The image quality of dedicated cone-beam breast CT (CBBCT) is fundamentally limited by substantial x-ray scatter contamination, resulting in cupping artifacts and contrast-loss in reconstructed images. Such effects obscure the visibility of soft-tissue lesions and calcifications, which hinders breast cancer detection and diagnosis. In this work, we propose to suppress x-ray scatter in CBBCT images using a deterministic forward projection model. Method: We first use the 1st-pass FDK-reconstructed CBBCT images to segment fibroglandular and adipose tissue. Attenuation coefficients are assigned to the two tissues based on the x-ray spectrum used for imaging acquisition, and is forward projected to simulate scatter-free primary projections. We estimate the scatter by subtracting the simulated primary projection from the measured projection, and then the resultant scatter map is further refined by a Fourier-domain fitting algorithm after discarding untrusted scatter information. The final scatter estimate is subtracted from the measured projection for effective scatter correction. In our implementation, the proposed scatter correction takes 0.5 seconds for each projection. The method was evaluated using the overall image spatial non-uniformity (SNU) metric and the contrast-to-noise ratio (CNR) with 5 clinical datasets of BI-RADS 4/5 subjects. Results: For the 5 clinical datasets, our method reduced the SNU from 7.79% to 1.68% in coronal view and from 6.71% to 3.20% in sagittal view. The average CNR is improved by a factor of 1.38 in coronal view and 1.26 in sagittal view. Conclusion: The proposed scatter correction approach requires no additional scans or prior images and uses a deterministic model for efficient calculation. Evaluation with clinical datasets demonstrates the feasibility and stability of the method. These features are attractive for clinical CBBCT and make our method distinct from other approaches. Supported partly by NIH R21EB019597, R21CA134128 and R01CA195512.The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
• Chueh, J. Y., Vedantham, S., Wakhloo, A. K., Carniato, S. L., Puri, A. S., Bzura, C., Coffin, S., Bogdanov, A. A., & Gounis, M. J. (2015). Aneurysm permeability following coil embolization: packing density and coil distribution. Journal of neurointerventional surgery, 7(9), 676-81.
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  Rates of durable aneurysm occlusion following coil embolization vary widely, and a better understanding of coil mass mechanics is desired. The goal of this study is to evaluate the impact of packing density and coil uniformity on aneurysm permeability.
• Dundamadappa, S. K., Thangasamy, S., Resteghini, N., Vedantham, S., Chen, A., & Takhtani, D. (2015). Skull fractures in pediatric patients on computerized tomogram: comparison between routing bone window images and 3D volume-rendered images. Emergency radiology, 22(4), 367-72.
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  Skull fracture is a common finding following head trauma. It has a prognostic significance and its presence points to severe trauma. Additionally, there is a greater possibility of detecting associated small underlying extra-axial hematomas and subtle injuries to the brain parenchyma. In pediatric patients, the presence of multiple open sutures often makes fracture evaluation challenging. In our experience, 3D volume (3DV)-rendered CT images complement routine axial bone window (RBW) images in detection and characterization of fractures. This is a multi-reader, multi-case, paired retrospective study to compare the sensitivity and specificity of RBW and 3DV images in detection of calvarial fractures in pediatric patients. A total of 60 cases (22 with fractures and 38 without) were analyzed. Two experienced neuroradiologists and a radiology trainee were the readers of the study. For all readers, the sensitivity was not statistically different between the RBW and the 3DV interpretations. For each reader, there was a statistically significant difference in the interpretation times between the RBW and the 3DV viewing formats. A greater number of sutural diastasis was identified on 3DV. We propose that 3DV images should be part of routine head trauma imaging, especially in the pediatric age group. It requires minimal post-processing time and no additional radiation. Furthermore, 3DV images help in reducing the interpretation time and also enhance the ability of the radiologist to characterize the calvarial fractures.
• Marosfoi, M. G., Korin, N., Gounis, M. J., Uzun, O., Vedantham, S., Langan, E. T., Papa, A. L., Brooks, O. W., Johnson, C., Puri, A. S., Bhatta, D., Kanapathipillai, M., Bronstein, B. R., Chueh, J. Y., Ingber, D. E., & Wakhloo, A. K. (2015). Shear-Activated Nanoparticle Aggregates Combined With Temporary Endovascular Bypass to Treat Large Vessel Occlusion. Stroke, 46(12), 3507-13.
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  The goal of this study is to combine temporary endovascular bypass (TEB) with a novel shear-activated nanotherapeutic (SA-NT) that releases recombinant tissue-type plasminogen activator (r-tPA) when exposed to high levels of hemodynamic stress and to determine if this approach can be used to concentrate r-tPA at occlusion sites based on high shear stresses created by stent placement.
• Marosfoi, M. G., Korin, N., Gounis, M. J., Uzun, O., Vedantham, S., Langan, E. T., Papa, A., Brooks, O. W., Johnson, C., Puri, A. S., Bhatta, D., Kanapathipillai, M., Bronstein, B. R., Chueh, J., Ingber, D. E., & Wakhloo, A. K. (2015). Shear-Activated Nanoparticle Aggregates Combined With Temporary Endovascular Bypass to Treat Large Vessel Occlusion. STROKE, 46(12), 3507-3513.
• Michaelsen, K. E., Krishnaswamy, V., Shi, L., Vedantham, S., Poplack, S. P., Karellas, A., Pogue, B. W., & Paulsen, K. D. (2015). Calibration and optimization of 3D digital breast tomosynthesis guided near infrared spectral tomography. Biomedical optics express, 6(12), 4981-91.
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  Calibration of a three-dimensional multimodal digital breast tomosynthesis (DBT) x-ray and non-fiber based near infrared spectral tomography (NIRST) system is challenging but essential for clinical studies. Phantom imaging results yielded linear contrast recovery of total hemoglobin (HbT) concentration for cylindrical inclusions of 15 mm, 10 mm and 7 mm with a 3.5% decrease in the HbT estimate for each 1 cm increase in inclusion depth. A clinical exam of a patient's breast containing both benign and malignant lesions was successfully imaged, with greater HbT was found in the malignancy relative to the benign abnormality and fibroglandular regions (11 μM vs. 9.5 μM). Tools developed improved imaging system characterization and optimization of signal quality, which will ultimately improve patient selection and subsequent clinical trial results.
• Vedantham, S. (2015). TU‐EF‐207‐05: Dedicated Cone‐beam Breast CT. Medical Physics, 42(6), 3623-3623. doi:10.1118/1.4925705
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  Breast imaging technology is advancing on several fronts. In digital mammography, the major technological trend has been on optimization of approaches for performing combined mammography and tomosynthesis using the same system. In parallel, photon-counting slot-scan mammography is now in clinical use and more efforts are directed towards further development of this approach for spectral imaging. Spectral imaging refers to simultaneous acquisition of two or more energy-windowed images. Depending on the detector and associated electronics, there are a number of ways this can be accomplished. Spectral mammography using photon-counting detectors can suppress electronic noise and importantly, it enables decomposition of the image into various material compositions of interest facilitating quantitative imaging. Spectral imaging can be particularly important in intravenously injected contrast mammography and eventually tomosynthesis. The various approaches and applications of spectral mammography are discussed. Digital breast tomosynthesis relies on the mechanical movement of the x-ray tube to acquire a number of projections in a predefined arc, typically from 9 to 25 projections over a scan angle of +/−7.5 to 25 degrees depending on the particular system. The mechanical x-ray tube motion requires relatively long acquisition time, typically between 3.7 to 25 seconds depending on the system. Moreover, mechanical scanning may have an effect on the spatial resolution due to internal x-ray filament or external mechanical vibrations. New x-ray source arrays have been developed and they are aimed at replacing the scanned x-ray tube for improved acquisition time and potentially for higher spatial resolution. The potential advantages and challenges of this approach are described. Combination of digital mammography and tomosynthesis in a single system places increased demands on certain functional aspects of the detector and overall performance, particularly in the tomosynthesis mode due to lower photon fluence per projection. This may require fast-frame acquisition and symmetric or asymmetric pixel binning in some systems. Recent studies investigated the performance of increased conversion layer thickness for contrast-enhanced imaging of the breast in dual-energy acquisition mode. In other direct conversion detectors operating in the avalanche mode, sensitivities close to the single photon response are also explored for mammography and breast tomosynthesis. The potential advantages and challenges of this approach are described. Dedicated breast CT brings x-ray imaging of the breast to true tomographic 3D imaging. It can eliminate the tissue superposition problem and does not require physical compression of the breast. Using cone beam geometry and a flat-panel detector, several hundred projections are acquired and reconstructed to near isotropic voxels. Multiplanar reconstruction facilitates viewing the breast volume in any desired orientation. Ongoing clinical studies, the current state-of-the art, and research to advance the technology are described. Learning Objectives: 1. To understand the ongoing developments in x-ray imaging of the breast 2. To understand the approaches and applications of spectral mammography 3. To understand the potential advantages of distributed x-ray source arrays for digital breast tomosynthesis 4. To understand the ongoing developments in detector technology for digital mammography and breast tomosynthesis 5. To understand the current state-of-the-art for dedicated cone-beam breast CT and research to advance the technology. Research collaboration with Koning Corporation.
• Vedantham, S., Karellas, A., Vijayaraghavan, G. R., & Kopans, D. B. (2015). Digital Breast Tomosynthesis: State of the Art. Radiology, 663-684.
• Vedantham, S., Shi, L., & Karellas, A. (2015). TU‐CD‐207‐10: Dedicated Cone‐Beam Breast CT: Design of a 3‐D Beam‐Shaping Filter. Medical Physics, 42(6), 3612-3612. doi:10.1118/1.4925629
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  Purpose: To design a 3 -D beam-shaping filter for cone-beam breast CT for equalizing x-ray photon fluence incident on the detector along both fan and cone angle directions. Methods: The 3-D beam-shaping filter was designed as the sum of two filters: a bow-tie filter assuming cylindrical breast and a 3D difference filter equivalent to the difference in projected thickness between the cylinder and the real breast. Both filters were designed with breast-equivalent material and converted to Al for the targeted x-ray spectrum. The bow-tie was designed for the largest diameter cylindrical breast by determining the fan-angle dependent path-length and the filter thickness needed to equalize the fluence. A total of 23,760 projections (180 projections of 132 binary breast CT volumes) were averaged, scaled for the largest breast, and subtracted from the projection of the largest diameter cylindrical breast to provide the 3D difference filter. The 3 -D beam shaping filter was obtained by summing the two filters. Numerical simulations with semi-ellipsoidal breasts of 10–18 cm diameter (chest-wall to nipple length=0.75 x diameter) were conducted to evaluate beam equalization. Results: The proposed 3-D beam-shaping filter showed a 140% -300% improvement in equalizing the photon fluence along the chest-wall to nipple (cone-angle) direction compared to a bow-tie filter. The improvement over bow-tie filter was larger for breasts with longer chest-wall to nipple length. Along the radial (fan-angle) direction, the performance of the 3-D beam shaping filter was marginally better than the bow-tie filter, with 4%-10% improvement in equalizing the photon fluence. For a ray traversing the chest-wall diameter of the breast, the filter transmission ratio was >0.95. Conclusion: The 3-D beam shaping filter provided substantial advantage over bow-tie filter in equalizing the photon fluence along the cone-angle direction. In conjunction with a 2-axis positioner, the filter can accommodate breasts of varying dimensions and chest-wall inclusion. Supported in part by NIH R01 CA128906 and R21 CA134128. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or NCI.
• Vedantham, S., Shi, L., & Karellas, A. (2015). WE-EF-207-06: Dedicated Cone-Beam Breast CT with Laterally-Shifted Detector: Monte Carlo Evaluation of X-Ray Scatter Distribution and Scatter-To-Primary Ratio. Medical Physics, 42(6), 3682-3682. doi:10.1118/1.4926013
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  Purpose: To determine the spatial distribution of x-ray scatter and scatter-to-primary ratio (SPR) in projections during cone-beam breast CT (CBBCT) with laterally-shifted detector that results in coronal (fan-angle) truncation. Methods: We hypothesized that CBBCT with coronal truncation would lower SPR due to reduction in irradiated breast volume, and that the location of maximum x-ray scatter fluence (scatter-peak) in the detector plane can be determined from the ratio of irradiated-to-total breast volume, breast dimensions and system geometry. Monte Carlo simulations (GEANT4) reflecting a prototype CBBCT system were used to record the position-dependent primary and scatter x-ray photon fluence incident on the detector without coronal truncation (full fan-angle, 2f=24-degrees) and with coronal truncation (fan-angle, f+ f=12+2.7-degrees). Semi-ellipsoidal breasts (10/14/18-cm diameter, chest-wall to nipple length: 0.75xdiameter, 2%/14%/100% fibroglandular content) aligned with the axis-of-rotation (AOR) were modeled. Mono-energy photons were simulated and weighted for 2 spectra (49kVp, 1.4-mm Al HVL; 60kVp, 3.76-mm Al HVL). In addition to SPR, the scatter maps were analyzed to identify the location of the scatter-peak. Results: For CBBCT without fan-angle truncation, the scatter-peaks were aligned with the projection of the AOR onto the detector for all breasts. With truncated fan-beam, the scatter-peaks were laterally-shifted from the projection of the AOR along the fan-angle direction by 14/38/70-pixels for 10/14/18-cm diameter breasts. The corresponding theoretical shifts were 14.8/39.7/68-pixels (p=0.47, 2-tailed paired-ratio t-test). Along the cone-angle, the shift in scatter-peaks between truncated and full-fan angle CBBCT were 2/2/4 -pixels for 10/14/18-cm diameter breasts. CBBCT with fan-angle truncation reduced SPR by 14/22/28% for 10/14/18-cm diameter breasts. 60kVp reduced SPR by 21–25% compared to 49kVp. Peak SPR for CBBCT with fan-angle truncation (60kVp) were 0.09/0.25/0.73 for 10/14/18-cm diameter breasts. Conclusion: CBBCT with laterally-shifted detector geometry and with appropriate kVp/beam quality reduces SPR. If residual scatter needs correction, the location corresponding to scatter-peak can be analytically computed. This work was supported in part by NIH R01 CA128906. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or NCI.
• Vedantham, S., Shi, L., Michaelsen, K. E., Krishnaswamy, V., Pogue, B. W., Poplack, S. P., Karellas, A., & Paulsen, K. D. (2015). Digital Breast Tomosynthesis guided Near Infrared Spectroscopy: Volumetric estimates of fibroglandular fraction and breast density from tomosynthesis reconstructions. Biomedical physics & engineering express, 1(4), 045202 (13 pages).
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  A multimodality system combining a clinical prototype digital breast tomosynthesis with its imaging geometry modified to facilitate near-infrared spectroscopic imaging has been developed. The accuracy of parameters recovered from near-infrared spectroscopy is dependent on fibroglandular tissue content. Hence, in this study, volumetric estimates of fibroglandular tissue from tomosynthesis reconstructions were determined. A kernel-based fuzzy c-means algorithm was implemented to segment tomosynthesis reconstructed slices in order to estimate fibroglandular content and to provide anatomic priors for near-infrared spectroscopy. This algorithm was used to determine volumetric breast density (VBD), defined as the ratio of fibroglandular tissue volume to the total breast volume, expressed as percentage, from 62 tomosynthesis reconstructions of 34 study participants. For a subset of study participants who subsequently underwent mammography, VBD from mammography matched for subject, breast laterality and mammographic view was quantified using commercial software and statistically analyzed to determine if it differed from tomosynthesis. Summary statistics of the VBD from all study participants were compared with prior independent studies. The fibroglandular volume from tomosynthesis and mammography were not statistically different (p=0.211, paired t-test). After accounting for the compressed breast thickness, which were different between tomosynthesis and mammography, the VBD from tomosynthesis was correlated with (r =0.809, p0.99, paired t-test), and was linearly related to, the VBD from mammography. Summary statistics of the VBD from tomosynthesis were not statistically different from prior studies using high-resolution dedicated breast computed tomography. The observation of correlation and linear association in VBD between mammography and tomosynthesis suggests that breast density associated risk measures determined for mammography are translatable to tomosynthesis. Accounting for compressed breast thickness is important when it differs between the two modalities. The fibroglandular volume from tomosynthesis reconstructions is similar to mammography indicating suitability for use during near-infrared spectroscopy.
• Vedantham, S., Shi, L., O'connell, A., & Karellas, A. (2015). MO‐F‐CAMPUS‐I‐01: Accuracy of Radiologists Interpretation of Mammographic Breast Density. Medical Physics, 42(6), 3574-3575. doi:10.1118/1.4925452
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  Purpose: Several commercial and non-commercial software and techniques are available for determining breast density from mammograms. However, where mandated by law the breast density information communicated to the subject/patient is based on radiologist's interpretation of breast density from mammograms. Several studies have reported on the concordance among radiologists in interpreting mammographic breast density. In this work, we investigated the accuracy of radiologist's interpretation of breast density. Methods: Volumetric breast density (VBD) determined from 134 unilateral dedicated breast CT scans from 134 subjects was considered the truth. An MQSA-qualified study radiologist with more than 20 years of breast imaging experience reviewed the DICOM “for presentation” standard 2-view mammograms of the corresponding breasts and assigned BIRADS breast density categories. For statistical analysis, the breast density categories were dichotomized in two ways; fatty vs. dense breasts where “fatty” corresponds to BIRADS breast density categories A/B, and “dense” corresponds to BIRADS breast density categories C/D, and extremely dense vs. fatty to heterogeneously dense breasts, where extremely dense corresponds to BIRADS breast density category D and BIRADS breast density categories A through C were grouped as fatty to heterogeneously dense breasts. Logistic regression models (SAS 9.3) were used to determine the association between radiologist's interpretation of breast density and VBD from breast CT, from which the area under the ROC (AUC) was determined. Results: Both logistic regression models were statistically significant (Likelihood Ratio test, p
• Vedantham, S., Spandre, G., Shrestha, S., Karellas, A., Brez, A., & Bellazzini, R. (2015). WE‐G‐204‐03: Photon‐Counting Hexagonal Pixel Array CdTe Detector: Optimal Resampling to Square Pixels. Medical Physics, 42(6), 3694-3694. doi:10.1118/1.4926087
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  Purpose: Detectors with hexagonal pixels require resampling to square pixels for distortion-free display of acquired images. In this work, the presampling modulation transfer function (MTF) of a hexagonal pixel array photon-counting CdTe detector for region-of-interest fluoroscopy was measured and the optimal square pixel size for resampling was determined. Methods: A 0.65mm thick CdTe Schottky sensor capable of concurrently acquiring up to 3 energy-windowed images was operated in a single energy-window mode to include ≥10 KeV photons. The detector had hexagonal pixels with apothem of 30 microns resulting in pixel spacing of 60 and 51.96 microns along the two orthogonal directions. Images of a tungsten edge test device acquired under IEC RQA5 conditions were double Hough transformed to identify the edge and numerically differentiated. The presampling MTF was determined from the finely sampled line spread function that accounted for the hexagonal sampling. The optimal square pixel size was determined in two ways; the square pixel size for which the aperture function evaluated at the Nyquist frequencies along the two orthogonal directions matched that from the hexagonal pixel aperture functions, and the square pixel size for which the mean absolute difference between the square and hexagonal aperture functions was minimized over all frequencies up to the Nyquist limit. Results: Evaluation of the aperture functions over the entire frequency range resulted in square pixel size of 53 microns with less than 2% difference from the hexagonal pixel. Evaluation of the aperture functions at Nyquist frequencies alone resulted in 54 microns square pixels. For the photon-counting CdTe detector and after resampling to 53 microns square pixels using quadratic interpolation, the presampling MTF at Nyquist frequency of 9.434 cycles/mm along the two directions were 0.501 and 0.507. Conclusion: Hexagonal pixel array photon-counting CdTe detector after resampling to square pixels provides high-resolution imaging suitable for fluoroscopy.
• Vijayaraghavan, G. R., Vedantham, S., Rangan, V., Karam, A., Zheng, L., Roychowdhury, A., & Hussain, S. (2015). Effect of needle gauge and lobe laterality on parenchymal liver biopsy outcome: a retrospective analysis. Abdominal imaging, 40(5), 1223-9.
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  To analyze the effect of lobe selection, needle gauge, and number of passes on procedure outcomes in terms of specimen length and post-procedure complications.
• Wakhloo, A. K., Vedantham, S., Puri, A. S., Narain, T., Marel, K. V., Howk, M., Gounis, M. J., & Bom, I. M. (2015). E-101 reduced patient radiation exposure during diagnostic and interventional x-ray angiography with novel imaging platform. Journal of NeuroInterventional Surgery, 7(Suppl 1), A87.1-A87. doi:10.1136/neurintsurg-2015-011917.176
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  Introduction Interventional neuroradiology provides increasingly safe and minimally invasive treatment options for neurovascular diseases, but the growing use of diagnostic and complicated fluoroscopy-guided procedures has led to heightened concerns over ionizing radiation exposure to patients and staff. AlluraClarity (Philips Healthcare) is a new commercially available angiographic imaging platform that addresses these concerns by employing novel algorithm- and hardware adjustments that allow for dose reduction while preserving image quality. In this study we report a comparison between AlluraClarity and its predecessor platform (Allura Xper) in a retrospective case review to assess the achieved reduction in mean radiation dose for various neurointerventional procedures. Materials and methods This review was conducted under an IRB-approved data registry. Cumulative dose area product (DAP) and total fluoroscopy time were collected for cases imaged on the Allura Xper (n = 659) and AlluraClarity (n = 329) platforms. Cases were stratified into 8 procedure categories: AVM embolization, carotid stenting, aneurysm coil embolization, diagnostic angiography, flow diverter implantation, stent coiling, thrombectomy, and other (see Table 1). Linear models were fitted to assess the effects of platform by procedure type on both cumulative DAP and total fluoroscopy time. Results Linear modeling showed that the AlluraClarity platform is associated with a significant (p Conclusion The introduction of the AlluraClarity imaging platform was associated with a significant reduction in radiation dose exposure for diagnostic and treatment procedures as compared to Allura Xper. While on average the cumulative DAP was reduced by 48%, this did not lead to an overall increase in total fluoroscopy time. Future work will incorporate the impact on staff dose and operator behavior in complex cases where patient exposure becomes a limiting factor. Disclosures K. van der Marel: None. S. Vedantham: None. I. van der Bom: 5; C; Philips Healthcare. M. Howk: None. T. Narain: None. M. Gounis: 1; C; Philips Healthcare, eV3/Covidien, NIH, Silk Road, Stryker Neurovascular. 2; C; Stryker Neurovascular, Codman Neurovascular. A. Puri: None. A. Wakhloo: 1; C; Philips Healthcare, NIH. 2; C; Stryker Neurovascular.
• Gounis, M. J., Vedantham, S., Weaver, J. P., Puri, A. S., Brooks, C. S., Wakhloo, A. K., & Bogdanov Jr., A. A. (2014). Myeloperoxidase in Human Intracranial Aneurysms Preliminary Evidence. STROKE, 45(5), 1474-1477.
• O'Connell, A. M., Karellas, A., & Vedantham, S. (2014). The Potential Role of Dedicated 3D Breast CT as a Diagnostic Tool: Review and Early Clinical Examples. BREAST JOURNAL, 20(6), 592-605.
• Vedantham, S., O'Connell, A. M., Shi, L., Karellas, A., Huston, A. J., & Skinner, K. A. (2014). Dedicated Breast CT: Feasibility for Monitoring Neoadjuvant Chemotherapy Treatment. Journal of clinical imaging science, 4, 64 (9 pages).
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  In this prospective pilot study, the feasibility of non-contrast dedicated breast computed tomography (bCT) to determine primary tumor volume and monitor its changes during neoadjuvant chemotherapy (NAC) treatment was investigated.
• Vedantham, S., Shi, L., & Karellas, A. (2014). Large-angle x-ray scatter in Talbot-Lau interferometry for breast imaging. Physics in medicine and biology, 59(21), 6387-400.
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  Monte Carlo simulations were used to investigate large-angle x-ray scatter at design energy of 25 keV during small field of view (9.6 cm × 5 cm) differential phase contrast imaging of the breast using Talbot-Lau interferometry. Homogenous, adipose and fibroglandular breasts of uniform thickness ranging from 2 to 8 cm encompassing the field of view were modeled. Theoretically determined transmission efficiencies of the gratings were used to validate the Monte Carlo simulations, followed by simulations to determine the x-ray scatter reaching the detector. The recorded x-ray scatter was classified into x-ray photons that underwent at least one Compton interaction (incoherent scatter) and Rayleigh interaction alone (coherent scatter) for further analysis. Monte Carlo based estimates of transmission efficiencies showed good correspondence [Formula: see text] with theoretical estimates. Scatter-to-primary ratio increased with increasing breast thickness, ranging from 0.11 to 0.22 for 2-8 cm thick adipose breasts and from 0.12 to 0.28 for 2-8 cm thick fibroglandular breasts. The analyzer grating reduced incoherent scatter by ~18% for 2 cm thick adipose breast and by ~35% for 8 cm thick fibroglandular breast. Coherent scatter was the dominant contributor to the total scatter. Coherent-to-incoherent scatter ratio ranged from 2.2 to 3.1 for 2-8 cm thick adipose breasts and from 2.7 to 3.4 for 2-8 cm thick fibroglandular breasts.
• Vedantham, S., Shi, L., Shenoy, A., Pogue, B. W., Paulsen, K. D., Michaelsen, K. E., Krishnaswamy, V., & Karellas, A. (2014). SU-E-I-54: Volumetric Breast Density: Comparison of Estimates From Tomosynthesis Reconstructions with Mammography. Medical Physics, 41(6), 142-142. doi:10.1118/1.4888004
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  Purpose: To measure the volumetric breast density (VBD) from digital breast tomosynthesis (DBT) reconstructions and compare with estimates from mammography. Methods: A kernel-based fuzzy c-means algorithm developed to segment DBT reconstructed slices to provide anatomic priors for near-infrared spectroscopy (NIRS) in a multimodality NIRS/DBT clinical-prototype imaging system was used to quantitate VBD. The VBD was determined from 17 DBT reconstructions of 11 breasts from 9 subjects (6 subjects—unilateral 2-view, 1 subject—unilateral craniocaudal (CC) view, 2 subjects—bilateral CC view) who underwent multimodality NIRS/DBT imaging. VBD from mammography (Quantra, Hologic Inc.) matched for subject, breast laterality and view was used for comparison. To account for differences in compressed breast thickness (T) between the modalities, the metric normalized VBD (nVBD = VBD/T) was considered. Results: All data satisfied normality assumption (Shapiro-Wilks, p>0.06). Pearson's correlation (r) and paired t-tests were used for analysis. The normalized VBD (nVBD) was statistically correlated (r=0.66, p
• Wakhloo, A. K., Vedantham, S., Puri, A. S., Gounis, M. J., & Chueh, J. (2014). E-060 Effect of Packing Density and Coil Uniformity on Coil Permeability. Journal of NeuroInterventional Surgery, 6(Suppl 1), A66.2-A67. doi:10.1136/neurintsurg-2014-011343.127
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  Introduction Durability of coiling procedures varies widely, and a better understanding of coil dynamics may help improve the treatment strategy. The goal of this study is to evaluate how packing density (PD) and coil uniformity impact aneurysm occlusion efficiency, which is conceptually associated with coil mass permeability. Materials and methods Experimental A1 aneurysm models were coiled using Guglielmi detachable coils (GDC) or Target coils. Coiled aneurysms were connected to a flow system filled with 1 µm fluorescent microsphere solution. The coil permeability was defined as the ratio of the microspheres that passed through the coil mass to the microspheres that circulated in the parent vessel. One neck section and 2 dome sections were obtained from each aneurysm for image analysis, including surface area fraction (SAF) and uniformity measurements. SAF was defined as the ratio of coil mass cross-sectional area to aneurysm cross-sectional area, and uniformity was determined from fractal-based heterogeneity measure, lacunarity. Lacunarity values closer to 0 indicate a homogeneously distributed coil mass. A statistical model was used to predict coil mass permeability as the outcome, with packing and uniformity measures as predictor variables. If the packing and uniformity measures exhibited statistically significant correlation, then principal component regression analysis was used for statistical modeling. Results All aneurysm PDs fell within the range of 27.1% to 45.5%, with a mean PD of 34.3 ± 4.4%. Permeability varied as a function of spatial coil uniformity for a given packing density (36%, Figure 1). With a higher uniformity (lacunarity: 0.06 vs. 0.09), the Target coiled aneurysm allowed less microspheres through the coil mass, as compared to the GDC coiled aneurysm. The lacunarity measures showed that in general, the coil distribution at the cross section of the neck was less uniform than in the dome. Coil mass permeability was statistically correlated with PD, SAF of dome and lacunarity of dome. Principal component regression analysis identified a primary factor with similar weights for PD, SAF of dome, and lacunarity of dome (range: 0.55–0.61). Coil mass permeability was modeled better with principal component regression incorporating the above measures (r 2 = 0.7) than linear regression with PD alone (r 2 = 0.46). The analysis indicates the importance of including a uniformity measure for coil distribution in the dome along with packing measures. Conclusion In addition to packing density, coil mass distribution has an important impact on excluding the aneurysm from the circulation. Disclosures J. Chueh: None. S. Vedantham: None. A. Puri: None. A. Wakhloo: 1; C; NIH, Philips Healthcare. 2; C; Stryker Neurovascular. M. Gounis: 1; C; eV3/Covidien, Philips Healthcare, NIH, Silk Road, Stryker Neurovascular. 2; C; fee-per-hour: Stryker Neurovascular, fee-per-hour: Codman Neurovascular.
• Shi, L., Vedantham, S., Karellas, A., & O'Connell, A. M. (2013). Technical Note: Skin thickness measurements using high-resolution flat-panel cone-beam dedicated breast CT. MEDICAL PHYSICS, 40(3).
• Vedantham, S., & Karellas, A. (2013). X-ray phase contrast imaging of the breast: Analysis of tissue simulating materials. MEDICAL PHYSICS, 40(4).
• Vedantham, S., Karellas, A., Emmons, M. M., Moss, L. J., Hussain, S., & Baker, S. P. (2013). Dedicated breast CT: geometric design considerations to maximize posterior breast coverage. Physics in medicine and biology, 58(12), 4099-118.
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  An Institutional Review Board-approved protocol was used to quantify breast tissue inclusion in 52 women, under conditions simulating both craniocaudal (CC) and mediolateral oblique (MLO) views in mammography, dedicated breast CT in the upright subject position, and dedicated breast CT in the prone subject position. Using skin as a surrogate for the underlying breast tissue, the posterior aspect of the breast that is aligned with the chest-wall edge of the breast support in a screen-film mammography system was marked with the study participants positioned for CC and MLO views. The union of skin marks with the study participants positioned for CC and MLO views was considered to represent chest-wall tissue available for imaging with mammography and served as the reference standard. For breast CT, a prone stereotactic breast biopsy unit and a custom-fabricated barrier were used to simulate conditions during prone and upright breast CT, respectively. For the same breast marked on the mammography system, skin marks were made along the breast periphery that was just anterior to the apertures of the prone biopsy unit and the upright barrier. The differences in skin marks between subject positioning simulating breast CT (prone, upright) and mammography were quantified at six anatomic locations. For each location, at least one study participant had a skin mark from breast CT (prone, upright) posterior to mammography. However for all study participants, there was at least one anatomic location where the skin mark from mammography was posterior to that from breast CT (prone, upright) positioning. The maximum amount by which the skin mark from mammography was posterior to breast CT (prone and upright) over all six locations was quantified for each study participant and pair-wise comparison did not exhibit statistically significant difference between prone and upright breast CT (paired t- test, p = 0.4). Quantitatively, for 95% of the study participants the skin mark from mammography was posterior to breast CT (prone or upright) by at the most 9 mm over all six locations. Based on the study observations, geometric design considerations targeting chest-wall coverage with breast CT equivalent to mammography, wherein part of the x-ray beam images through the swale during breast CT are provided. Assuming subjects can extend their chest in to a swale, the optimal swale-depth required to achieve equivalent coverage with breast CT images as mammograms for 95% of the subjects varies in the range of ~30-50 mm for clinical prototypes and was dependent on the system geometry.
• Vedantham, S., Shi, L., & Karellas, A. (2013). WE‐G‐103‐04: X‐Ray Scatter in Differential Phase‐Contrast Breast Imaging Using Gratings‐Based Interferometer. Medical Physics, 40(6), 510-510. doi:10.1118/1.4815664
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  Purpose: To determine the x‐ray scatter content in differential phase‐contrast imaging of the breast using a gratings‐based interferometer. Methods: X‐ray scatter during small field‐of‐view (9.6×5‐cm) differential phase‐contrast breast imaging with a gratings‐based interferometer (25‐keV design) was determined using GEANT4 Monte Carlo (MC) toolkit. The duty‐cycles of source (G0), phase (G1) and analyzer (G2) gratings were 0.25, 0.5 and 0.5, respectively. All gratings were planar and fabricated from 0.675‐mm thick silicon wafers. MC estimated transmission efficiencies of the gratings in parallel‐beam geometry were validated with theoretical estimates. After validation, their transmission efficiencies were determined in cone‐beam geometry. Position‐independent estimates of scatter and primary photons at the detector plane were obtained with 2 to 8 cm thick adipose and fibroglandular breasts and without the breast in the x‐ray beam. The recorded x‐ray scatter was analyzed after classification as photons that underwent at least one Compton interaction (incoherent scatter) and as photons that underwent Rayleigh interaction alone (coherent scatter). While G2 is needed in practice, simulations were conducted without G2 to determine its role in scatter reduction. Results: In parallel‐beam geometry, Monte Carlo estimated transmission efficiencies showed good correspondence (r2>0.99) with theory. In cone‐beam geometry, the transmission efficiencies of G0, G1 and G2 gratings were 0.16, 0.7 and 0.25, respectively. Position‐independent estimates of scatter‐to‐primary ratio were 0.08 without the breast, and increased from 0.13 (0.15) to 0.25 (0.31) for 2 to 8 cm thick adipose (fibroglandular) breasts. Coherent scatter was the dominant contributor to total scatter with coherent‐to‐incoherent scatter ratio ranging from 1.65 (1.94) to 1.8 (2.04) for adipose (fibroglandular) breasts. The G2 grating reduced incoherent scatter by ∼5% to 24% for 2 to 8‐cm breasts. Conclusion: The 0.675‐mm thick silicon wafer contributed to ∼30% reduction in transmission efficiency for each grating. The G2 grating reduces the incoherent scatter at the detector plane. Supported in part by the National Institutes of Health (NIH) grants R01 CA128906 and R21 CA134128. The contents are solely the responsibility of the authors and do not represent the official views of the NIH or NCI.
• Vedantham, S., Shi, L., Glick, S. J., & Karellas, A. (2013). Scaling-law for the energy dependence of anatomic power spectrum in dedicated breast CT. MEDICAL PHYSICS, 40(1).
• Vedantham, S., Shi, L., Karellas, A., O'Connell, A. M., & Conover, D. L. (2013). Personalized estimates of radiation dose from dedicated breast CT in a diagnostic population and comparison with diagnostic mammography. PHYSICS IN MEDICINE AND BIOLOGY, 58(22), 7921-7936.
• Vedantham, S., Shi, L., Konate, S., & Karellas, A. (2013). SU‐E‐I‐01: Radiation Dose Reduction and Image Quality Evaluation of Coronal Truncated Projections in Cone‐Beam Dedicated Breast CT. Medical Physics, 40(6), 124-125. doi:10.1118/1.4814101
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  Purpose: To investigate the radiation dose reduction and the effect of weighting schemes on image quality in cone‐beam dedicated breast CT acquired with coronal truncated projections that is similar in concept as extended field‐of‐view imaging with laterally‐shifted flat‐panel detectors. Methods: Three pre‐weighting schemes were implemented in conjunction with filtered backprojection (FBP) reconstruction to study the effect of coronal truncation in dedicated breast CT. If the fan‐angle of the non‐truncated projections is represented as 2f (24‐degrees), then coronal truncations corresponding to f+0.25, f+1.5, and f+2.7‐degrees were investigated. Monte Carlo simulations using the GEANT4 toolkit were used to determine the radiation dose reduction at the aforementioned truncations. Projection images of a numerical phantom with dimensions representative of an average pendant breast containing six spherical signal objects in a homogenous background were reconstructed without and with truncation. Cone‐beam projections from a diagnostic dedicated breast CT exam acquired with fan‐angle of 2f were truncated at the aforementioned fan‐angles and reconstructed. Phantom and clinical images were analyzed for artifacts and the visibility of signal features. Results: For an average 14‐cm diameter, 15% fibroglandular breast, the estimated dose reduction at fan‐angles of f+0.25, f+1.5, and f+2.7‐degrees were 47%, 34% and 21%, respectively. The severity of artifacts increased with decreasing fan‐angle. The choice of weighting scheme does not appear to have a substantial effect on mitigating artifacts. At fan‐angles of f+1.5 and above, shading artifacts were subtle and could not be easily discerned. The signal objects in the phantom and the microcalcification in the clinical images were discernible. For 10, 14 and 18 cm diameter, 15% fibroglandular breasts, the radiation dose reduction at fan‐angle of f+1.5‐degrees were 27%, 34% and 37%, respectively. Conclusion: There exists a potential to reduce radiation dose by approximately 30% from cone‐beam dedicated breast CT acquired with coronal truncated projections. Supported in part by the National Institutes of Health (NIH) grants R01 CA128906 and R21 CA134128. The contents are solely the responsibility of the authors and do not represent the official views of the NIH or the NCI.
• van, d., Hou, S. Y., Puri, A. S., Spilberg, G., Ruijters, D., van, d., Carelsen, B., Vedantham, S., Gounis, M. J., & Wakhloo, A. K. (2013). Reduction of Coil Mass Artifacts in High-Resolution Flat Detector Conebeam CT of Cerebral Stent-Assisted Coiling. AMERICAN JOURNAL OF NEURORADIOLOGY, 34(11), 2163-2170.
• Vedantham, S., & Karellas, A. (2012). SU-E-I-61: Phantom Design for Phase Contrast Breast Imaging.. Medical physics, 39(6Part5), 3638-3639. doi:10.1118/1.4734777
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  Phase contrast breast imaging has the potential to improve visualization of anatomic structures. While the physics is well-understood, there are several choices for implementation. In order to evaluate these choices, it is essential to design a phantom for phase contrast imaging with appropriate breast-equivalent materials..Phantoms for mammography use materials that mimic the x-ray attenuation properties of breast tissue. Hence, the refractive index decrement (delta) was determined for breast tissues of varying glandular fraction [Hammerstein, Radiology 130(2):485-91, 1979] for the energy range (5-100 KeV) relevant to mammography and breast CT using XOP software (Version 2.3, ESRF, France) and compared to that of commonly used phantom materials. Delta for 50% and 70% glandular breast-equivalent material (CIRS Inc., Norfolk, VA), solid water, BR-12, polymethyl methacrylate (PMMA), beeswax (C46H92O2, density: 0.97 g/cm3 ) and paraffin wax (C25H52, density: 0.95 g/cm3 ) were determined. Microcalcifications in vivo are either of oxalate or phosphate composition. Delta of calcium oxalate monohydrate (COM) and calcium hydroxyapatite (CH) were determined and compared with that of calcium carbonate, gold and aluminum..In terms of delta, paraffin wax (4% higher) and beeswax (4% higher) best simulated 50% and 100% glandular breast, respectively. Delta of other commonly used phantom materials such as 50% and 70% glandular breast-equivalent material, solid water, and BR-12 were two orders of magnitude higher, and that of PMMA was 28% higher, than 50% glandular breast tissue. For microcalcifications, delta of gold was 4.6 to 6.5 times higher than that of COM and CH, respectively. Delta of aluminum and calcium carbonate were found to straddle that of COM and CH..For phase contrast imaging, a phantom comprising paraffin wax to simulate 50% glandular background tissue, beeswax to simulate a mass equivalent to 100% glandular tissue, and calcium carbonate or aluminum to simulate microcalcifications is appropriate. Supported in part by the National Institutes of Health (NIH) grants R01 CA128906 and R21 CA134129. The contents are solely the responsibility of the authors and do not represent the official views of the NIH or NCI.
• Vedantham, S., Karellas, A., Conover, D. O., & Shi, L. (2012).

  DEDICATED BREAST CT: ANATOMIC POWER SPECTRUM

  . Proceedings: 2012 CT Meeting.
• Vedantham, S., Shi, L., Karellas, A., & Noo, F. (2012). Dedicated breast CT: radiation dose for circle-plus-line trajectory. MEDICAL PHYSICS, 39(3), 1530-1541.
• Vedantham, S., Shi, L., Karellas, A., & O'Connell, A. M. (2012). Dedicated breast CT: Fibroglandular volume measurements in a diagnostic population. MEDICAL PHYSICS, 39(12), 7317-7328.
• Vedantham, S., Shi, L., O'connell, A., & Karellas, A. (2012). TU-E-217BCD-05: Dedicated Breast CT: Skin Thickness Measurements in a Diagnostic Population.. Medical physics, 39(6Part24), 3914-3915. doi:10.1118/1.4735977
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  To test the hypothesis that the mean skin thickness determined using cone-beam dedicated breast CT varied between breasts with malignant, hyperplasia and benign pathology, and to determine the appropriate skin thickness for Monte Carlo based estimation of normalized glandular dose coefficients..Breast skin thickness was estimated in 137 women scheduled for biopsy (BI-RADS 4 or 5), who underwent unilateral cone-beam dedicated CT of the breast to be biopsied, after providing written informed consent and in adherence to an IRB-approved protocol. Pathology results were available for 132 women and there were 38 malignancies. A previously reported method [Huang et al., Med Phys 35(4): 1199-206, 2008] was applied to coronal (transverse) images reconstructed to 0.273 mm voxel size. The accuracy of the method was determined by imaging two phantoms of differing wall thickness and shape. For each breast, the mean, intra-breast standard deviation (SD) and the median skin thickness were computed. The mean skin thickness and associated confidence intervals (CI) in our study population were obtained from the mean skin thickness of each breast..The estimated mean wall thicknesses for both phantoms were within +/-1% of the measured thickness. At the 0.05 level (ANOVA), the skin thickness means did not vary significantly with pathology (p=0.61). For each breast, the median, mean and intra-breast SD, in mm, were in the range [0.87,2.23], [0.87,2.34], and [0.22,0.85], respectively. From all 137 women, the mean +/- inter-breast SD and 95% CI were 1.44+/-0.25 and [1.40,1.48], respectively..The skin thickness means were not different between breasts with malignant and non-malignant pathology. Our estimate of mean skin thickness is in agreement with a previous report. Skin thickness of approximately 1.45 mm, rather than the standard 4 mm [Wu et al., Radiology 193:83-9, 1994], is appropriate for Monte Carlo based determination of normalized glandular dose coefficients. Supported in part by the National Institutes of Health (NIH) grants R01 CA128906 and R21 CA134129. The contents are solely the responsibility of the authors and do not represent the official views of the NIH or NCI.
• Karellas, A., Glick, S. J., Vedantham, S., Shi, L., Noo, F., Karellas, A., & Glick, S. (2011). SU‐E‐I‐150: Cone‐Beam Artifacts in Dedicated Breast CT. Medical Physics, 38(6), 3430-3431. doi:10.1118/1.3611724
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  Purpose: Cone‐beam CT with circular trajectory is susceptible to cone‐angle related artifacts that affect quantitative imaging. These artifacts were quantified under conditions relevant to dedicated breast CT for full and short‐scans. Methods: Three sets of numerical phantoms (0.2‐mm voxels) were used: (1) cylindrical Defrise phantom of 14‐cm diameter and 10.6‐cm length inclusive of 2‐mm skin, with alternating 4‐mm coronal layers of fixed (0.15) and variable (0 to 1, in steps of 0.1) glandular fraction breast tissue; (2) semi‐ellipsoidal Defrise phantom with dimensions matched to the cylindrical phantom for a realistic pendant‐breast geometry; (3) 20 surgical mastectomy specimens based numerical phantoms. Source‐to‐rotational axis and source‐to‐detector distances of 65‐cm and 100‐cm, respectively, were used. Noise‐free simulations were performed at 30‐keV, with the phantoms co‐aligned to rotational axis, using an ideal detector (0.4‐mm pixels), and without the confounding effects of focal spot blur (point source) and x‐ray scatter. Constant angular sampling of 1.2‐degrees was used resulting in 300 and 165 projections for full‐scan and short‐scan (198‐ degrees). Reconstructions were performed using Hamming‐windowed FDK‐algorithm with short‐scan using Parker weights. For the Defrise phantoms, the cone‐angle dependence of the artifacts was analyzed using percent difference at the rotational axis between the reconstructions and phantoms, and by visual inspection. For the mastectomy specimens, power spectral analysis was performed. Results: For Defrise phantoms, increasing attenuation difference between layers resulted in higher inaccuracies (artifacts). Cylinder resulted in higher inaccuracies compared to semi‐ ellipsoid particularly near maximum cone‐angle. Visual inspection and power spectral analysis indicate that the spatial distribution of these artifacts is different between full and short‐scans. Conclusions: Cone‐beam artifacts at breast CT relevant conditions are observed. They depend on object shape, and attenuation difference of the tissues within the object. These artifacts must be remediated as they may impact task‐specific assessment and can profoundly affect quantitative imaging. Supported by NIH/NCI R01CA128906. The contents are sole responsibility of the authors and do not represent the official views of the NIH or NCI. SG: Research contract with Toshiba Medical Research Institute.
• Wakhloo, A. K., Vedantham, S., Karellas, A., & Gounis, M. J. (2011). SU‐E‐I‐97: A Protocol for Attenuation Characterization of Neurovascular Devices under Fluoroscopic Conditions. Medical Physics, 38(6), 3418-3418. doi:10.1118/1.3611671
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  Purpose: Current approaches for ensuring adequate visualization of neuroendovascular devices that are implanted under fluoroscopic guidance, such as stents and flow diverters, are based on ad hoc methods and measures. Lack of specific standards makes it difficult to determine the adequacy of device contrast under clinical conditions. Inadequate device contrast due to low attenuation may result in increased radiation dose to the patient either due to prolonged fluoroscopy or due to the use of high dose‐ rate imagingsequence. Alternatively, this may lead to inaccurate positioning of these devices within cerebrovascular structures with potential impact on clinical outcome. We developed a protocol and applied it for evaluating such devices. Methods: The protocol comprises three parts: quantitative measurement of equivalent attenuation (in mm of Al) under conditions used for characterizing imaging system performance (RQA5 of IEC standards), visual assessment of device contrast in homogenous background (water phantom) of anatomically relevant thickness, and visual assessment of the device contrast with anatomic background. Ten devices (2 Ni‐Ti stents, 7 Co‐Cr and 1 Ni‐Ti flow diverters) were assessed using this protocol. Results: Quantitative assessment of the stents showed substantial equivalent attenuation of the device end/tip marker (Pt) bands but poor attenuation characteristics of the device body. The flow diverters demonstrated improved attenuation along the device body than the stents. The newer generation of flow diverters with Pt wires interwoven with the Co‐Cr wires demonstrated improved attenuation characteristics compared to previous generation which did not include Pt wires. Visual assessment under homogenous (16 cm water phantom) and anatomic background (skull phantom immersed in 16 cm water) provided qualitative confirmation. Conclusions: The proposed protocol with further refinements can serve as the basis for evaluating the adequacy of x‐ray contrast of neuroendovascular devices that are implanted under fluoroscopic guidance. Devices provided by Surpass Medical LTD. (Tel Aviv, Israel). Research supported in part by NIH/NCI R01CA128906 and NIH/NIBIB R21EB007767. The contents are sole responsibility of the authors and do not reflect the official views of the NIH, NCI or NIBIB. MG: Has been a consultant per hour for Micrus Endovascular and Codman Neurovascular; receives research support from Stryker Neurovascular, Micrus Endovascular, Codman Neurovascular, Neurointerventional Technologies, Neuravi, Thrombolysis Scientific Inc, and Concentric Medical. AW: Has been a consultant per hour for Codman Neurovascular, Stryker Neurovascular, Boston Medical Associates, Surpass Medical Ltd; holds ownership interest in Surpass Medical Ltd; receives research support from Philips Healthcare.
• Vedantham, S., & Karellas, A. (2010). Modeling the Performance Characteristics of Computed Radiography (CR) Systems. IEEE TRANSACTIONS ON MEDICAL IMAGING, 29(3), 790-806.
• Vedantham, S., & Karellas, A. (2010). TH‐D‐201B‐02: Modeling the Performance Characteristics of a “Dual‐Side” Read Computed Radiography System for Mammography. Medical Physics, 37(6), 3472-3472. doi:10.1118/1.3469561
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  Purpose: To determine objective image quality metrics such as modulation transfer function(MTF) and detective quantum efficiency (DQE) using an image formation model for optimizing the imaging performance of “dual‐side” read computed radiography(CR)systems.Method and Materials: A parallel‐cascades based linear systemsmodel that included “granular” noise associated with grain size variations, wherein several model parameters were estimated using Monte Carlo techniques, was used to determine the objective performance of a “dualside” read CRsystem employing a granular storage phosphor. In our simulations, an imaging plate (IP) comprising 150 fm thick BaFBr(0.85)I(0.15) layer, 10⌈m protective polyethylene terephthalate (PET) layer, and 320 ⌈ m support layer (PET) was imaged with mammography x‐ray spectrum matched to Fetterly's experimental work [Med Phys 30: 1843, 2003]. A 2mW, 680nm laser with Gaussian intensity (l/e2 diameter: 50 ⌈ m) was orthogonally incident on the IP with a dwell time of 5 ⌈ s and the IP was “readout” with 50 ⌈ m sampling. Signals from top and bottom readouts were combined to maximize the Noise Equivalent Quanta [Arakawa, Proc. SPIE 3659: 572 (1999)]. Results: Our results indicated a 10% MTF of ∼7 cy/mm, a maximum DQE(0) of ∼0.6 at 1mR, and a DQE(0) of ∼0.55 at clinically relevant 9.4mR. DQE(0) decreased with increasing exposure due to granular noise, consistent with theory and experimental data. While the specifications of FCR5000MA (Fuji Medical Systems) were unknown to us, our results are in remarkable agreement with Fetterly. Conclusion: A model such as that addressed here enables for improved understanding of the effect of storage phosphor physical properties and CR reader parameters on objective image quality metrics for “dual‐side” read CRsystems, and may allow designing new CRsystems. Supported in part by NIH R01EB004105. Contents are solely the responsibility of the authors and do not represent the views of NIH or NIBIB.
• Vedantham, S., & Karellas, A. (2010). WE‐C‐201C‐01: Perspective on the Developing Modalities for Breast Cancer Imaging. Medical Physics, 37(6), 3424-3425. doi:10.1118/1.3469382
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  Perspective on the Developing Modalities for Breast CancerImagingDigital mammography has already become the new standard, replacing screen‐film for breast cancer screening, and for diagnostic work‐up of suspicious findings. New digital imaging technologies may use x‐ray beam characteristics such as tungsten target, silver filtration, and higher kVp; in ways that represent a departure from the long established screen‐film techniques. Representing a logical evolution from two‐dimensional to tomographic and 3D imaging of the breast, breast tomosynthesis and dedicated breast CT are currently investigated as potential replacements or adjuncts to mammography.Mammography (screen‐film or digital) is the single most effective tool for the detection of occult breast cancer with an overall sensitivity as high as about 85% for older women and about 60% or lower for women under the age of 50 years (Rosenberg RD et al. Radiology. 1998;209:511–8, Pisano E et al. N. Engl. J. Med. 2005;353: 1773–83). Attempts to increase sensitivity have included the use of intravenously injected (IV) contrast with digital mammography,tomosynthesis or breast CT but these efforts are in the research stage. With improved hardware and image acquisition techniques, the role of IVcontrast injected MRI is gradually expanding as a diagnostic tool, and it is also recommended for screening of high risk patients, due to its high sensitivity. Ultrasound, a well established modality for diagnostic work‐up is evolving from the conventional pulse echo‐based approach to elasticity imaging and ultrasoundCT of the breast. Breast scintigraphy with a dedicated camera is now in clinical use and it receives much attention as an adjunct to mammography. Other technologies that include diffuse optical tomography as a stand‐alone modality or in conjunction with MRI or with x‐ray imaging are currently under investigation. We are likely to see an increasing use of alternative imaging approaches in conjunction with mammography,ultrasound and MRI, the three essential modalities for breast cancer detection and for diagnostic work‐up of positive findings. Learning Objectives: 1. Appreciate recent advances in the physics and engineering in x‐ray detector technology that contributed to the development of digital mammography,tomosynthesis and dedicated breast CT. 2. Recognize the potential quantitative applications and important limitations of the x‐ray based breast imaging modalities. 3. Appreciate recent technological developments in current clinical non‐x‐ray modalities such as MRI and ultrasound and their increasingly important role in breast cancerimaging. 4. Gain perspective on some emerging modalities such as optical diffuse tomography and their potential role in the detection and diagnosis of breast cancer.
• Wakhloo, A. K., Vedantham, S., Karellas, A., Gounis, M. J., & Bom, M. J. (2010). SU-GG-I-181: Noise Characterization of a Clinical Flat-Panel Cone-Beam Computed Tomography (CBCT) System. Medical Physics, 37(6), 3143-3143. doi:10.1118/1.3468217
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  Purpose: To quantitatively characterize the noise performance of a neurointerventional c‐arm based flat‐panel cone‐beam computed tomography (FP‐CBCT) system with an aim of exploring the feasibility of performing cerebral blood volume (CBV) calculations. Method and Materials: Five CBCT scans of ∼11 cm diameter water phantom positioned at the isocenter were acquired at 120kVp and reconstructed to 5123 matrix with 0.33mm voxels. Central Regions of Interest (ROIs) of 1933 matrix corresponding to ∼(63mm)3 were extracted from each scan. Spatial uniformity was determined using the standard deviation (SD) in Hounsfield Units (HU) and repeatability was measured using the root‐mean‐squared deviation (RMSD) of mean signal and using the coefficient of variation (COV) of SD metrics. 3‐D noise power spectra (NPS) were computed with and without subtraction of the average ROI volume from each ROI, which allowed determination of structural noise.Results: Mean signal and SD determined from (193)3 matrix and averaged over the 5 scans were 9.3HU (range: 8.4–10.3; RMSD=0.5) and 19.1HU (range: 19.05–19.15; COV
• Karellas, A., & Vedantham, S. (2008). Breast cancer imaging: A perspective for the next decade. MEDICAL PHYSICS, 35(11), 4878-4897.
• Karellas, A., & Vedantham, S. (2008). Breast cancer imaging: a perspective for the next decade. Medical physics, 35(11), 4878-97.
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  Breast imaging is largely indicated for detection, diagnosis, and clinical management of breast cancer and for evaluation of the integrity of breast implants. In this work, a prospective view of techniques for breast cancer detection and diagnosis is provided based on an assessment of current trends. The potential role of emerging techniques that are under various stages of research and development is also addressed. It appears that the primary imaging tool for breast cancer screening in the next decade will be high-resolution, high-contrast, anatomical x-ray imaging with or without depth information. MRI and ultrasonography will have an increasingly important adjunctive role for imaging high-risk patients and women with dense breasts. Pilot studies with dedicated breast CT have demonstrated high-resolution three-dimensional imaging capabilities, but several technological barriers must be overcome before clinical adoption. Radionuclide based imaging techniques and x-ray imaging with intravenously injected contrast offer substantial potential as a diagnostic tools and for evaluation of suspicious lesions. Developing optical and electromagnetic imaging techniques hold significant potential for physiologic information and they are likely to be of most value when integrated with or adjunctively used with techniques that provide anatomic information. Experimental studies with breast specimens suggest that phase-sensitive x-ray imaging techniques can provide edge enhancement and contrast improvement but more research is needed to evaluate their potential role in clinical breast imaging. From the technological perspective, in addition to improvements within each modality, there is likely to be a trend towards multi-modality systems that combine anatomic with physiologic information. We are also likely to transition from a standardized screening, where all women undergo the same imaging exam (mammography), to selection of a screening modality or modalities based an individual-risk or other classification.
• Sechopoulos, I., Suryanarayanan, S., Vedantham, S., D'Orsi, C. J., & Karellas, A. (2008). Radiation dose to organs and tissues from mammography: Monte Carlo and phantom study. RADIOLOGY, 246(2), 434-443.
• Sechopoulos, I., Vedantham, S., Suryanarayanan, S., D'Orsi, C. J., & Karellas, A. (2008). Monte Carlo and phantom study of the radiation dose to the body from dedicated CT of the breast. RADIOLOGY, 247(1), 98-105.
• Sechopoulos, I., Suryanarayanan, S., Vedantham, S., D'Orsi, C. J., & Karellas, A. (2007). Scatter radiation in digital tomosynthesis of the breast. MEDICAL PHYSICS, 34(2), 564-576.
• Sechopoulos, I., Suryanarayanan, S., Vedantham, S., D'Orsi, C., & Karellas, A. (2007). Computation of the glandular radiation dose in digital tomosynthesis of the breast. MEDICAL PHYSICS, 34(1), 221-232.
• Suryanarayanan, S., Karellas, A., Vedantham, S., Sechopoulos, I., & D'Orsi, C. J. (2007). Detection of simulated microcalcifications in a phantom with digital mammography: Effect of pixel size. RADIOLOGY, 244(1), 130-137.
• Vedantham, S., Suryanarayanan, S., Sechopoulos, I., & Karellas, A. (2007). SU‐FF‐I‐97: Feasibility of Low Dose X‐Ray Contrast Enhanced Digital Mammography with Gold Nanoparticles. Medical Physics, 34(6), 2360-2360. doi:10.1118/1.2760474
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  Purpose: To study the feasibility of low dose x‐ray contrast enhanced digital mammography (CEDM) with goldnanoparticles as a contrast agent. Method and Materials:Contrast enhanced digital mammography (CEDM) with iodine based agents is currently being explored. However, novel materials such as goldnanoparticles seem very promising for CEDM because of their high x‐ray absorption in the mammographic energy range. Computer generated volumetric breast compositions of 50% and 75% mean glandular fractions and thickness of 5 and 7.5 cm were analytically ray‐traced at various mono‐energetic conditions and spectrally combined with simulated power‐law noise to create 2D projection images with mammogram‐like texture at 100 micron pixel resolution. The projection images were modified in accordance with the system resolution and noise power spectrum of a clinical full‐field digital mammography system (Senographe 2000D, GE Healthcare, WI) and used to generate imagedata sets. A 6 mm diameter spherical lesion with an inherent glandular fraction of 65% and 100% was used for the 50% and 75% glandular breast conditions respectively. Lesions with contrast agent concentrations of 0.5, 1, 2 and 4 mg/cc were generated. A 26 kVp, Mo/Mo and 31 kVp, Rh/Rh x‐ray spectra were used to generate full‐dose images (∼2 mGy mean glandular dose) for the 5 and 7.5 cm‐thick breasts respectively. A Laguerre‐Gauss Channelized Hotelling observer (LG‐CHO) was implemented to compute the signal‐to‐noise ratio (SNR). Results: Good contrast visualization was observed at ∼0.13 mGy per image frame with CEDM. Contrast agent concentrations between 0.5–2 mg/cc in the lesion resulted in much higher SNRs compared to full dose mammography.Conclusion: This work suggests favorable properties for goldnanoparticles as an x‐ray contrast agent for CEDM. This could potentially benefit high‐risk patient groups such as women with dense breasts. Other potential applications include progress monitoring in neo‐adjuvant treatment regimens.
• Vedantham, S., Suryanarayanan, S., Sechopoulos, I., & Karellas, A. (2007). TH-C-L100F-10: Monte Carlo Coupled Modeling of a Computed Radiography System. Medical Physics, 34(6), 2621-2621. doi:10.1118/1.2761637
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  Purpose: To develop a model that allows for understanding the physical properties and the effect of readout parameters on objective image quality metrics of a ‘flying spot’ computed radiography(CR)system.Method and Materials: A Monte Carlo simulation method [Fasbender et al., Nucl Instrum Methods Phys Res A 512 (2003): 610–8] that describes the optical transport in a ‘flying spot’ readout was implemented by adapting the code of Jacques [Photochem Photobiol 67 (1998), 23–32]. This program was coupled with a ‘parallel‐cascades’ approach [Yao and Cunningham, Med Phys 28 (2000): 2020–38] to predict systemMTF and DQE. Grain size was assumed to follow a normal distribution in the imaging plate (IP) and granular noise was determined using the works of Nutting and Siedentopf. Additional assumptions include, orthogonal x‐ray incidence, no scatter, no glare, no defects in the IP, a constant discharge fraction, and a linear readout amplifier were assumed for a linear and wide‐sense stationary process. X‐ray spectra representative of radiography and mammography were used in the simulations. Published or estimated parameters that correspond to two common IPs were compiled from multiple sources. Results: For radiography with 0.2‐mm sampling, model results showed good agreement with published literature values for systemMTF (r>0.99) and moderate agreement for DQE (r = 0.75 to 0.99) over four orders of incident exposure (0.03 to 30‐mR). For mammography with 0.1‐mm sampling, model results showed good agreement with published literature values for systemMTF (r>0.99) and for DQE (r = 0.95 to 0.99) over two orders of incident exposure (∼1 to 100‐mR). Conclusion: The proposed model facilitates identifying factors that could improve CR performance. Accurate estimates of IP parameters and model improvements such as incorporation of Lubberts' effect could further improve model accuracy. Supported in part by NIH R01EB004015 and Georgia Cancer Coalition award.
• Vedantham, S., Suryanarayanan, S., Sechopoulos, I., Karellas, A., & D'orsi, C. J. (2007). Erratum: "Scatter radiation in digital tomosynthesis of the breast" [Med. Phys., - (2007)].. Medical physics, 34(9), 3697. doi:10.1118/1.2759600
• Vedantham, S., Suryanarayanan, S., Sechopoulos, I., Karellas, A., & D'orsi, C. J. (2007). WE‐E‐L100J‐05: Radiation Dose to Tissues From Mammography. Medical Physics, 34(6), 2606-2606. doi:10.1118/1.2761580
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  Purpose: To compute the radiation dose to different tissues of the body from a standard mammogram.Method and Materials: Using the Geant4 Monte Carlo toolkit, a simulation was developed in which the human body was represented using a mathematical anthropomorphic phantom. A total of 66 different organs and tissues were simulated, including the uterus, which was used to compute the dose to the fetus during early‐stage pregnancy. The imaged breast was represented as compressed, and in both the cranio‐caudal and the medio‐lateral oblique views. At each energy level, the simulation emitted 60 million monochromatic x‐rays and recorded the location of each interaction and the amount of energy deposited. The dose to the red bone marrow and to the bone surfaces of each bone was estimated separately. The monochromatic data was used to compute the resulting dose for different typical polyenergetic mammographic spectra, and the values were normalized to the resulting glandular dose to the breast, resulting in the dose ratio. The effectiveness of using a lead shield between the patient and the x‐ray field was also investigated. Results: Only 16 organs and skeletal tissues received a dose higher than 0.10% of the glandular dose to the breast. Of the organs, the contralateral breast received the highest dose ratio with 0.62%. Of the skeletal tissues, the sternum received the highest dose, with a dose ratio of 2.36% to the bone surface and 0.56% to the bone marrow. The dose to the uterus and fetus received a maximum dose ratio of
• Karellas, A., Vedantham, S., Sechopoulos, I., & Suryanarayanan, S. (2006).

  Analysis of wavelet-based compression in digital mammography on a clinical gray-scale display

  . 3rd Americas Display Engineering and Applications Conference, ADEAC 2006.
• Suryanarayanan, S., Karellas, A., Vedantham, S., & Sechopoulos, I. (2006). Theoretical analysis of high-resolution digital mammography. PHYSICS IN MEDICINE AND BIOLOGY, 51(12), 3041-3055.
• Vedantham, S. (2006). Book Review - Practical Radiography, by Peter Hertrich. Journal of Applied Clinical Medical Physics, 7(2), 103-104. doi:10.1120/jacmp.v7i2.2253
• Vedantham, S., Suryanarayanan, S., Sechopoulos, I., & Karellas, A. (2006). SU‐DD‐A4‐05: Characterization of X‐Ray Scatter and Glandular Dose in Digital Tomosynthesis for Breast Imaging Using Monte Carlo Simulations. Medical Physics, 33(6), 1990-1990. doi:10.1118/1.2240153
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  Purpose: To study the characteristics of x‐ray scatter and glandular dose in digital tomosynthesis for breast imaging.Method and Materials:Monte Carlo simulations of x‐ray transport in breast tomosynthesis were performed using the Geant4 package [Agostinelli et al, Nucl Instrum Meth A 506: 250–303, 2003]. Scatter‐to‐primary ratio (SPR) maps, maximum SPR, scatter point spread functions (PSF) and glandular dose to the breast were computed at several projection angles while varying compressed breast size, thickness, glandularity and x‐ray spectrum. For validation, the SPR and scatter PSF for the planar mammography view (0 degrees) for various setups were compared with published values [Boone et al, Med Phys 27(10): 2408‐16, 2000 and 27(8): 1818–1831, 2000]. Results: SPR maps and PSF show variations with increasing projection angle, with apparent asymmetry appearing at projection angles beyond 10 degrees. When the projection angle is increased from 0 to 21 ‐degrees, while the breast thickness encountered by the central ray increases by 7.1%, the maximum SPR for a semi‐circular 10 cm radius breast increases by 10.1% and 18.8 % for breast thicknesses of 2 cm and 8 cm, respectively. Dose deposition shows a decrease, varying by 3.8–7.6% for the same thicknesses and projection angles. Conclusion: Since the use of an anti‐scatter grid is not easy to implement in tomosynthesisimaging, the development of software‐based post‐acquisition scatter reduction is important, which requires a good understanding of the scatter effects. This work characterizes the scatter signal present in tomosynthesisimages and shows that x‐ray scatter affects each projection angle differently and therefore each projection must be corrected separately, using appropriate prior knowledge. Decreased glandular dose with increasing projection angle must be taken into account when planning a tomosynthesis clinical protocol. Research supported in part by: NIH‐NIBIB Grant RO1‐ EB002123 and the Georgia Cancer Coalition.
• Vedantham, S., Suryanarayanan, S., Sechopoulos, I., & Karellas, A. (2006). SU‐FF‐I‐12: Validation of Geant4's Predictions On X‐Ray Scatter and Glandular Dose in Pendant‐Geometry Cone‐Beam Breast CT. Medical Physics, 33(6), 1999-1999. doi:10.1118/1.2240250
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  Purpose: The Geant4 toolkit is a freely available, widely supported base package for the simulation of particles through matter. This study aimed to test Geant4's accuracy by comparing its predictions for glandular dose and x‐ray scatter in pendant‐geometry cone‐beam breast CT against previously published experimental and simulated data. Method and Materials: We performed Monte Carlo simulations using the Geant4 package [Agostinelli et al, Nucl Instrum Meth A 506: 250–303, 2003] to recreate the conditions of three previously published papers on breast CT dose and scatter. Geant4's scatter simulations are compared against experimental data [Kwan et al, Med Phys 32(9): 2967–2975, 2005], while the dose results are compared against Monte Carlo simulations based on other codes [Boone et al, Med Phys 31(2): 226–235, 2004; Thacker et al, Phys Med Biol 49: 5433–5444, 2004]. The compared scatter results include scatter‐to‐primary ratio profiles for breasts of different sizes, glandularity and incident x‐ray spectra. For the dose comparisons, we compared Geant4's monochromatic results with the monochromatic results reported by the two previously published papers. Results: Geant4 matches the reported experimental SPR profiles to an accuracy of 1.6–16.7% (μ=9.2%, σ=5.4%). The sources for observed deviations include inexact re‐creation of the experimental setup and lack of specific information on the x‐ray spectra used in the experiments. The dose results agree with Boone's published results within 0.7–12.3% (μ=5.3%, σ=4.2%) and with Thacker's to within 1.2–22.3% (μ=10.8%, σ=8.8%). Conclusion: The data comparison suggests that Geant4 can be used to predict x‐ray scatter and dose deposition in low energy experiments such as dedicated breast CT. Given the availability, support and flexibility of the Geant4 toolkit, the use of this package for simulation of breast CT studies can be very useful to researchers in the field. Research supported in part by: NIH‐NIBIB Grant RO1‐EB002123 and the Georgia Cancer Coalition.
• Vedantham, S., Suryanarayanan, S., Sechopoulos, I., & Karellas, A. (2006). WE‐E‐330D‐03: Feasibility of High‐Resolution Contrast Enhanced Digital Mammography. Medical Physics, 33(6), 2252-2252. doi:10.1118/1.2241793
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  Purpose: This study is aimed at investigating the feasibility of high‐resolution contrast enhanced digital mammography (CEDM). Method and Materials: Recent studies report certain promising aspects of contrastmammography [Jong et al., Radiology 228, 842–50, 2003] for identifying subtle lesions that might not be detectable by conventional mammography. In this study we investigate certain physical aspects of high‐resolution CEDM. The objective was to study the feasibility of high resolution and low dose CEDM with acceptable contrast characteristics. We used a prototype imager [Vedantham et al., Med Phys 31, 1462–72, 2004] that consists of a 2 × 2, CCD array. The imager was operated in a 78 μm mode by pixel binning. Computational studies with a 49 kVp, W spectrum with 0.6 mm Cu added filtration (1st HVL: 1.9 mm of Al) indicated dose levels in the range of 0.1–0.5 mGy for a 5 cm thick, 50% glandular breast for the entire mammography exam. Theoretical modeling was performed using the parallel cascaded approach described by Cunningham and Yao [Proc. SPIE 3336, 220–30, 1998, Med Phys 28, 2020–38, 2001] for various physical conditions. In addition, experimental evaluation of the physical characteristics of the imager was conducted. Results: The resolution characteristics at 10% MTF was ∼7.8 and ∼4.2 cycles/mm and the DQE(0) estimate was ∼0..4 and ∼0.65 for 150 and 450 μm thick CsI:Tl scintillators respectively. Model results for pixel size range of 39–156 μm and CsI:Tl thickness range of 150–300 μm indicate that a 250–300 μm thick CsI scintillator with an imager pixel size of 78 μm could potentially offer a reasonable trade‐off between spatial resolution and DQE(f) characteristics. Conclusion: The results suggest that high‐resolution CEDM appears to be feasible at dose levels substantially lower then digital mammography. This research was supported in part by: NIH‐NIBIB Grant RO1‐EB002123 and the Georgia Cancer Coalition.
• Chowdhury, S. M., Vedantham, S., Suryanarayanan, S., Sumrain, S., Shah, N., Medithe, A., Kumar, V., Guntupalli, R., Giakos, G. C., Endorf, R. E., & Chowdhury, S. (2005). An efficient, novel microstrip collector architecture for digital radiographic imaging CZT semiconductor sensors. IEEE Transactions on Instrumentation and Measurement, 54(3), 1144-1149. doi:10.1109/tim.2005.847210
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  The purpose of this paper is to study the impact of a novel microstrip collector design on the temporal response of CdZnTe (CZT) semiconductor detectors for digital radiographic imaging applications. The experimental results of this paper clearly indicate a significant improvement of the temporal response of the CZT imaging detectors due to the enhanced collection efficiency.
• Suryanarayanan, S., Karellas, A., Vedantham, S., & Onishi, S. K. (2005). High-resolution imager for digital mammography: physical characterization of a prototype sensor. Physics in medicine and biology, 50(17), 3957-69.
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  The physical performance characteristics of a high-resolution sensor module for digital mammography were investigated. The signal response of the imager was measured at various detector entrance air kerma and was found to be linear. The spatial resolution was determined by measuring the presampling modulation transfer function, MTF(f), of the system. The noise power spectra, NPS(f), of the system were estimated using 26 kVp: Mo/Mo, 28 kVp: Mo/Rh and 30 kVp: Rh/Rh, with polymethyl methacrylate (PMMA) 'tissue equivalent material' of thickness 20, 45 and 57 mm for each of three x-ray spectra at detector entrance air kerma in the range between approximately 80.2 and 92.3 microGy. The noise equivalent quanta, NEQ(f), and detective quantum efficiencies, DQE(f), for the various spectral conditions were computed. In addition, dose dependence of NPS(f) and DQE(f) was studied at various detector entrance air kerma ranging from 9.4 to 169.7 microGy. A spatial resolution of about 10 cycles mm(-1) was obtained at the 10% MTF(f) level. A small increase in NEQ(f)was observed under higher energy spectral conditions while the DQE(f) decreased marginally. For a given spectrum, increasing PMMA filtration produced negligible change in DQE(f). The estimated DQE values at zero frequency were in the range between 0.45 and 0.55 under the conditions investigated in this study.
• Suryanarayanan, S., Karellas, A., Vedantham, S., Waldrop, S. M., & D'Orsi, C. (2005). Detection of simulated lesions on data-compressed digital mammograms. RADIOLOGY, 236(1), 31-36.
• Vedantham, S., Suryanarayanan, S., Sechopoulos, I., & Karellas, A. (2005). SU-FF-I-35: Scatter Correction For Digital Tomosynthesis. Medical Physics, 32(6), 1911-1912. doi:10.1118/1.1997515
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  Purpose: To investigate post acquisition scatter correction for digital tomosynthesis breast imaging.Method and Materials:Images of a composite phantom that was fabricated for evaluating digital breast tomosynthesis and used in a previous contrast‐detail (CD) study [Suryanarayanan et al., Acad Radiol 7: 1085–1097, 2000] were used to test the scatter correction method. These images were acquired using a prototype full‐field digital mammography (FFDM) system (GEMedical Systems, Milwaukee, WI) without an anti‐scatter grid. The phantom comprised of a centrally placed CD insert (MedOptics, Tucson, AZ), blocks of cluttered paraffin and polymethyl methacrylate (PMMA), and beeswax surrounding it to provide a total phantom thickness of 54 mm. A set of 7 projection images of the phantom were acquired over an angular range of ± 18° at 60 intervals at 26 kVp, MoMo, and 32 mAs/view. The projection data sets were corrected for scatter using the scatter correction technique described by Trotter et al. [Proc. SPIE, vol. 4682: 469–478, 2002] and processed with an adaptive noise filter. The projection images were then reconstructed using back‐projection and iterative restoration methods using Tuned Aperture Computed Tomography (TACT) [Webber et al., J. Digit. Imaging, 13: 90–97, 2000] software (developed by R.L. Webber, Wake Forest University, NC). The contrast‐to‐noise (CNR) ratio, signal‐to‐noise ratio (SNR), and % contrast were computed for one of the targets (2.32 mm diameter and 0.24 mm depth). Results: The uncorrected projection data set reconstructed with back‐projection resulted in CNR = 3.0, SNR = 30.4, and % contrast = 11.1, while the scatter corrected and processed projection images yielded CNR = 10.2, SNR =60.7, and %contrast = 20.2. Conclusion: The results of this study indicate improved SNR,CNR, and % contrast after scatter correction in tomosynthesis. We are currently implementing and evaluating other scatter correction and reconstruction methods for digital tomosynthesis.
• Suryanarayanan, S., Karellas, A., & Vedantham, S. (2004). Physical characteristics of a full-field digital mammography system. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 533(3), 560-570.
• Suryanarayanan, S., Karellas, A., Vedantham, S., Waldrop, S. M., & D'Orsi, C. (2004). A perceptual evaluation of JPEG 2000 image compression for digital mammography: Contrast-detail characteristics. JOURNAL OF DIGITAL IMAGING, 17(1), 64-70.
• Vedantham, S., Karellas, A., & Suryanarayanan, S. (2004). Solid-state fluoroscopic imager for high-resolution angiography: Parallel-cascaded linear systems analysis. MEDICAL PHYSICS, 31(5), 1258-1268.
• Vedantham, S., Karellas, A., Suryanarayanan, S., & Onishi, S. K. (2004). Solid-state fluoroscopic imager for high-resolution angiography: Physical characteristics of an 8cmX8cm experimental prototype. MEDICAL PHYSICS, 31(6), 1462-1472.
• Evans, E. A., Chowdhury, S. M., Vedantham, S., Ugweje, O. C., Suryanarayanan, S., Sumrain, S., Shah, N., Patnekar, N., Orozco, A. L., Moholkar, A., Mehta, K., Kumar, V., Guntupalli, R., Giakos, G. C., Evans, E. A., Chowdhury, S., & Abreu-garcia, J. A. (2003). Intrinsic sensitivity of Cd/sub 1-x/Zn/sub x/Te semiconductors for digital radiographic imaging. IEEE Transactions on Instrumentation and Measurement, 52(5), 1559-1565. doi:10.1109/tim.2003.818563
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  The intrinsic sensitivity of cadmium zinc telluride (Cd/sub 1-x/Zn/sub x/Te) semiconductor detectors has been experimentally measured, within the X-ray diagnostic energy range. The results of this study indicate that the intrinsic efficiency of Cd/sub 1-x/Zn/sub x/Te can be increased by optimizing geometrical and physical detection parameters such as X-ray irradiation geometry, detector thickness, and applied electric field. These results indicate that Cd/sub 1-x/Zn/sub x/Te is a suitable candidate for digital imaging applications.
• Evans, E. A., Vedantham, S., Suryanarayanan, S., Shah, N., Patnekar, N., Orozco, A., Nemer, R., Mehta, K., Kumar, V., Guntupalli, S., Giakos, G. C., Fraiwan, L., Evans, E. A., Dasgupta, A., & Chowdhury, S. (2003). Signal dispersion measurements on the gas detector volume of a dual-energy multimedia digital imaging sensor. IEEE Transactions on Instrumentation and Measurement, 52(5), 1566-1572. doi:10.1109/tim.2003.818564
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  In this study, experimental results on the signal dispersion of a gas detector volume of a multimedia imaging detector, operating on both gaseous and solid-state ionization principles, with specific emphasis on single X-ray exposure dual-energy radiography, are presented. The results of this study indicate that the gas detector volume of the multimedia detector technology exhibits excellent signal characteristics suitable for a large number of imaging applications. By focusing on the gas detector element, drift distance causes significant effects on both the amplitude and full-width at half maximum due to mobility dispersion and space-charge. An improved signal results with increasing gas pressure.
• Vedantham, S., Karellas, A., & Suryanarayanan, S. (2003). Attenuation characteristics of fiberoptic plates for digital mammography and other X-ray imaging applications. Journal of X-ray science and technology, 11(4), 219-30.
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  Spatially coherent fiberoptic plates are important components of some charge-coupled device (CCD)-based x-ray imaging systems. These plates efficiently transmit scintillations from the phosphor, and also filter out x-rays not absorbed by the phosphor, thus protecting the CCD from direct x-ray interaction. The thickness of the fiberoptic plate and the CCD package present a significant challenge in the design of a digital x-ray cassette capable of insertion into the existing film-screen cassette holders of digital mammography systems. This study was performed with an aim to optimize fiberoptic plate thickness. Attenuation measurements were performed on nine fiberoptic plates varying in material composition that exhibit desirable optical characteristics such as good coupling efficiency. Mammographic spectra from a clinical mammographic system and an Americium-241 (Am-241) source (59.54 KeV) were used. The spectra were recorded with a high-resolution cadmium zinc telluride (CZT)-based spectrometer and corrected for dead time and pile-up. The linear attenuation coefficients varied by a factor of 3 in the set of tested fiberoptic plates at both mammographic energies and 59.54 keV. Our results suggest that a 3-mm thick high-absorption plate might provide adequate for shielding at mammographic energies. A thickness of 2-mm is feasible for mammographic applications with further optimization of the fiberoptic plate composition by incorporating non-scintillating, high-atomic number material. This would allow more space for cooling components of the cassette and for a more compact device, which is critical for clinical implementation of the technology.
• Vedantham, S., Ved, H., Suryanarayanan, S., Karellas, A., & D'orsi, C. J. (2003). A perceptual evaluation of JPEG2000 image compression for digital mammography. Journal of Digital Imaging, 16, 97-98.
• Suryanarayanan, S., Karellas, A., Vedantham, S., Ved, H., Baker, S. P., & D'Orsi, C. (2002). Flat-panel digital mammography system: Contrast-detail comparison between screen-film radiographs and hard-copy images. RADIOLOGY, 225(3), 801-807.
• Evans, E. A., Vedantham, S., Suryanarayanan, S., Sumrain, S., Shah, N., Russo, F., Patnekar, N., Passerini, A. G., Nemer, R., Nataraj, K., Mehta, K., Guntupalli, R., Giakos, G. C., Evans, E. A., Endorf, R. J., & Chowdhury, S. (2001). Detected contrast and dynamic range measurements of CdZnTe semiconductors for flat-panel digital radiography. IEEE Transactions on Instrumentation and Measurement, 50(6), 1604-1609. doi:10.1109/19.982953
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  The detected contrast and dynamic ranges of Cd/sub 1-x/Zn/sub x/Te semiconductor detectors have been measured, within the X-ray diagnostic energy range, using a contrast sensitivity phantom. The aim of this study is to optimize the image quality parameters of these solid state ionization devices for flat panel digital radiographic applications. The experimental results of this study indicate that Cd/sub 1-x/Zn/sub x/Te detectors have excellent detected contrast response and large dynamic range.
• Evans, E. A., Vedantham, S., Suryanarayanan, S., Sumrain, S., Shah, N., Russo, F., Patnekar, N., Passerini, A. G., Odogba, J., Nemer, R., Nataraj, K., Mehta, K., Guntupalli, R., Giakos, G. C., Evans, E. A., & Chowdhury, S. (2001). Optimization of the temporal response of II-VI direct type semiconductor detectors for flat-panel pulsed X-ray imaging. IEEE Transactions on Instrumentation and Measurement, 50(6), 1610-1614. doi:10.1109/19.982954
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  The rising and falling edges of detected signal pulses have been measured utilizing X-ray ionization of a planar Cd/sub 1-x/Zn/sub x/Te system under different irradiation geometries, at different detector thicknesses, and applied electric fields. The experimental results of this study indicate that the time response of the CdZnTe based X-ray system is suitable for digital pulsed radiographic applications.
• Suryanarayanan, S., Karellas, A., Vedantham, S., Baker, S. P., Glick, S. J., D'Orsi, C., & Webber, R. L. (2001). Evaluation of linear and nonlinear tomosynthetic reconstruction methods in digital mammography. ACADEMIC RADIOLOGY, 8(3), 219-224.
• Vedantham, S., Suryanarayanan, S., & Karellas, A. (2001). Theoretical analysis of hybrid flat-panel detector arrays for digital x-ray fluoroscopy: general sys. IEEE Sensors Journal, 1(2), 168-174. doi:10.1109/jsen.2001.936934
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  Semiconductor flat-panel detector arrays are being investigated for applications in digital x-ray medical imaging. This paper describes the system architecture and theoretical signal and noise processes of a proposed hybrid cadmium zinc telluride (CZT) based CMOS active pixel sensor (APS) array for fluoroscopy. Sim- ulations were performed using an 80-kVp-tungsten spectrum and a 200- m pixel. The proposed system appears to exhibit favor- able characteristics in terms of charge generation, lag, quantum noise, and other electronic sources of noise, and compared well with other direct conversion detectors. Overall, we expect the system to be x-ray quantum noise limited under diagnostic exposure condi- tions for fluoroscopy and conclude that the proposed imager ex- hibits promising characteristics for applications in diagnostic x-ray imaging.
• Vedantham, S., Suryanarayanan, S., Sumrain, S., Shah, N., Scheiber, C., Patnekar, N., Passerini, A. G., Nemer, R., Nataraj, K., Mehta, K., Giakos, G. C., & Chowdhury, S. (2001). Signal-to-noise measurements utilizing a novel dual-energy multimedia detector. IEEE Transactions on Instrumentation and Measurement, 50(4), 910-914. doi:10.1109/19.948298
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  Dual-energy measurements are presented utilizing a novel slot-scan digital radiographic imaging detector, operating on gaseous solid state ionization principles. The novel multimedia detector has two basic functional components: a noble gas-filled detector volume operating on gas microstrip principles, and a solid state detector volume. The purpose of this study is to investigate the potential use of this multimedia detector for enhanced dual-energy imaging. The experimental results indicate that the multimedia detector exhibits a large subtracted signal-to-noise ratio. Although the intrinsic merit of this device is being explored for medical imaging, potential applications of the multimedia detector technology In other industrial areas, such as aerospace imaging, aviation security, and surveillance, are also very promising.
• Suryanarayanan, S., Karellas, A., Vedantham, S., Glick, S. J., D'Orsi, C., Baker, S. P., & Webber, R. L. (2000). Comparison of tomosynthesis methods used with digital mammography. ACADEMIC RADIOLOGY, 7(12), 1085-1097.
• Vedantham, S., Karellas, A., Suryanarayanan, S., Albagli, D., Han, S., Tkaczyk, E. J., Landberg, C. E., Opsahl-Ong, B., Granfors, P. R., Levis, I., D'Orsi, C., & Hendrick, R. E. (2000). Full breast digital mammography with an amorphous silicon-based flat panel detector: Physical characteristics of a clinical prototype. MEDICAL PHYSICS, 27(3), 558-567.
• Vedantham, S., Karellas, A., Suryanarayanan, S., D'Orsi, C., & Hendrick, R. E. (2000). Breast imaging using an amorphous silicon-based full-field digital mammographic system: Stability of a clinical prototype. JOURNAL OF DIGITAL IMAGING, 13(4), 191-199.
• Vedantham, S., Karellas, A., Suryanarayanan, S., Levis, I., Sayag, M., Kleehammer, R., Heidsieck, R., & D'Orsi, C. (2000). Mammographic imaging with a small format CCD-based digital cassette: Physical characteristics of a clinical system. MEDICAL PHYSICS, 27(8), 1832-1840.
• Vedantham, S., Tkaczyk, E. J., Suryanarayanan, S., Opsahl-ong, B., Levis, I., Landberg, C. E., Karellas, A., Hendrick, R. E., Han, S., Granfors, P. R., D'orsi, C. J., & Albagli, D. (2000). Response to “Comment on ‘Full breast digital mammography with an amorphous silicon‐based flat panel detector: Physical characteristics of a clinical prototype”’ [Med. Phys. 27, 2192 (2000)]. Medical Physics, 27(9), 2193-2193. doi:10.1118/1.1290033
• Suryanarayanan, S., Karellas, A., Vedantham, S., Glick, S. J., D'Orsi, C., & Webber, R. L. (1999). Comparison of contrast-detail characteristics of tomosynthetic reconstruction techniques for digital mammography. RADIOLOGY, 213P, 368-369.
• Vega-lozada, V., Vedantham, S., Suryanarayanan, S., Sridhar, M., Shah, N., Odogba, J., Khyati, M., Guntupalli, R., Giakos, G. C., Dasgupta, A., & Chowdhury, S. (1999). Timing characteristics of a Cd/sub 1-x/Zn/sub x/Te detector-based X-ray imaging system. IEEE Transactions on Instrumentation and Measurement, 48(5), 909-914. doi:10.1109/19.799646
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  The timing characteristics of a planar Cd/sub 1-x/Zn/sub x/Te sample at each frequency of a scanning square-wave test pattern, has been measured. This study is aimed at evaluating the speed characteristics of a Cd/sub 1-x/Zn/sub x/Te detector for X-ray imaging and computed tomographic (CT) applications. The experimental results of this study indicate that the temporal response of a Cd/sub 1-x/Zn/sub x/Te detector based X-ray system, improves significantly by optimizing the X-ray tube and detector parameters.
• Giakos, G. C., Dasgupta, A., Suryanarayanan, S., Chowdhury, S., Guntupalli, R. K., Vedantham, S., Pillai, B., Passalaqua, A., & Kollipara, S. (1998). Sensitometric response of Cd1-xZnxTe detectors for chest radiography. IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, 47(1), 252-255.
• Giakos, G. C., Vedantham, S., Chowdhury, S., Odogba, J., Dasgupta, A., Pillai, B., Sheffer, D. B., Nemer, R. E., Guntupalli, R. K., Suryanarayanan, S., Vega-Lozada, V., Endorf, R. J., & Passalaqua, A. (1998). Study of detection efficiency of Cd(1-x)Zn(x)Te detectors for digital radiography. IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, 47(1), 244-251.
• Vega-lozada, V., Vedantham, S., Suryanarayanan, S., Sumrain, S., Sha, N., Patnekar, N., Odogba, J., Mehta, K., Guntupalli, R., Giakos, G. C., Dasgupta, A., & Chowdhury, S. (1998). Temporal response of a Cd 1-xZn xTe detector system for digital radiography. Journal of X-ray Science and Technology, 8(4), 241-251.
• Giakos, G. C., Pillai, B., Chowdhury, S., Vedantham, S., Dasgupta, A., Kollipara, S., Passalaqua, A., & Endorf, R. J. (1997). Cd1-xZnx Te Detectors for Digital X-Ray Chest Imaging. Journal of X-ray science and technology, 7(3), 305-15.
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  Radiographic studies with the aim of optimizing the imaging potential of Cd1-xZnxTe detectors for digital chest radiography have been performed. A geometrical chest phantom has been designed, and the dependence of both the signal-to-noise ratio and contrast resolution of a planar Cd1-xZnxTe detector on the phantom thickness has been experimentally determined. Specifically, the detected signal and noise contributions were measured and related to phantom thickness. The results of this study indicate that Cd1-xZnxTe detectors exhibit both high signal-to-noise ratio and contrast resolution. At present time, several studies are in process to experimentally identify and quantify the imaging potential of Cd1-xZnxTe detectors for digital radiographic applications.
• Giakos, G. C., Pillai, B., Chowdhury, S., Vedantham, S., Dasgupta, A., Sheffer, D. B., Davros, W. J., Passalaqua, A., & Endorf, R. J. (1997). Contrast Study of CdZnTe Detectors for Digital Mammography. Journal of X-ray science and technology, 7(3), 317-26.
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  Experiments have been performed with the aim of optimizing the image quality parameters of CdZnTe detectors for digital mammography. A geometrical breast phantom has been designed, and the dependence of the contrast resolution of a planar CdZnTe detector on the phantom thickness has been experimentally determined. Specifically, the detected signal and noise contributions were measured and related to phantom thickness. The results of this study indicate that the CdZnTe detectors exhibit a high contrast resolution. On the other hand, the dynamic range of this detector can be improved significantly by further implementation of the data acquisition electronics.
• Giakos, G. C., Pillai, B., Vedantham, S., Chowdhuri, S., Dasgupta, A., Richardson, R. B., Ghotra, P., Endorf, R. J., Passalaqua, A., & Davros, W. J. (1997). Optimization of Cd1-xZnxTe Detectors for Digital Radiography. Journal of X-ray science and technology, 7(1), 37-49.
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  In this study, measurements of the electrical and detection parameters of the Cd1-xZnxTe detectors, within the x-ray diagnostic energy range, have been performed with the aim of optimizing the image quality parameters of these solid-state-ionization detectors. Namely, the leakage current and system capacitance of the x-ray imaging system have been measured as they relate to signal parameters. Similarly, the detected signal and noise contributions were measured and related to the radiation exposure and tube current setting. Furthermore, the detector contrast has been experimentally determined. The experimental results indicate that Cd1-xZnxTe detectors have low leakage current, high resistivity, and high detector contrast resolution. Therefore, they appear to be very attractive for imaging applications with applications in x-ray digital radiography.
• Giakos, G. C., Pillai, B., Vedantham, S., Chowdhuri, S., Odogba, J., Dasgupta, A., Vega-Lozada, V., Guntupalli, R., Suryanarayanan, S., Endorf, R. J., Passalaqua, A., & Kollipara, S. (1997). Electric Field Dependence on Charge Collection of CdZnTe X-Ray Detectors. Journal of X-ray science and technology, 7(2), 198-210.
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  In this study, the electric field dependence on the charge collection process of CdZnTe detectors, at different x-ray tube settings, within the x-ray diagnostic energy range, is investigated. In addition, the detector contrast at different applied bias voltages and x-ray tube settings have been experimentally determined. The experimental results suggest that an efficient charge collection process is obtained by increasing the applied bias voltage. Once the applied bias voltage is sufficiently high, charge collection becomes complete and the detector operates in the saturation region. This is a prerequisite for high contrast and spatial resolution. As a result, the detector contrast is enhanced significantly. Therefore, CdZnTe detectors appear to be potential candidates for digital radiographic applications.
• Giakos, G. C., Vedantham, S., Pillai, B., Chowdhury, S., Sheffer, D. B., Dasgupta, A., Endorf, R. J., Passalaqua, A., & Kollipara, S. (1997). Signal Dependence on Irradiation Geometry of Cd1-xZnxTe Detectors for Digital X-Ray Imaging. Journal of X-ray science and technology, 7(3), 295-304.
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  CdZnTe is one of the most promising semiconductor material in the field of digital X-ray imaging, and may be operated at room temperature. To improve the detector characteristics, ternary systems such as Cd1-xZnxTe were grown by the high pressure Bridgman (HPG) technique. The signal performance characteristics of quasi-resistive Cd1-xZnxTe semiconductor detectors, was studied at different directions of irradiation, within the X-ray diagnostic energy range. The experimental results suggest that the total efficiency of these semiconductor detectors depends upon the energy absorption efficiency as well as the charge collection efficiency. This imaging detector allows one to investigate methods to improve the detection and imaging performance parameters as part of the development of an X-ray imaging system.
• Giakos, G. C., Ghotra, P., Pillai, B., Chowdhury, S., Vedantham, S., Dibianca, F. A., Jordan, L. M., Devidas, S., Nagarajan, S., & Endorf, R. J. (1996). Line spread function study of kinestatic charge detectors operating at high gas pressures. Journal of X-ray science and technology, 6(4), 343-58.
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  A systematic study of the line spread function (LSF) in the drift direction of a high-pressure ionization chamber for x-ray detection and imaging is presented. Experimental results, obtained by operating a KCD krypton-filled detector at pressures up to 60 atm and constant electric field-to-gas pressure ratio, indicate that the width of the LSF increases with the drift distance and decreases with increasing pressure, both effects being quite large. The hypothesis of this paper is that, at sufficiently high pressures, formation of clusters of molecular ions with a unique or narrowed mobility distribution take place by means of energy exchange mechanisms. Therefore, the LSF of the ionic signal becomes narrower and the FWHM of the ionic signal improves significantly with increasing gas pressure. This research is aimed at investigating methods to improve the spatial resolution as part of the development of a large field-of-view prototype digital radiographic scanner operating on kinestatic charge detection principles.

Proceedings Publications

• Chow, H., Vedantham, S., Roe, D., Tseng, H., Chiang, J. A., Centuori, S. M., Chalasani, P., Garcia, D. O., Garcia, D. O., Chalasani, P., Centuori, S. M., Chiang, J. A., Tseng, H., Roe, D., Vedantham, S., & Chow, H. (2023). Feasibility of quantitative breast density measurements in obese women with dedicated cone-beam breast CT.. In 2023 Program of the 10th International Breast Density & Cancer Risk Assessment Workshop, a21.
• Fu, Z., Tseng, H., & Vedantham, S. (2023). An Attenuation Field Network reconstruction using short-scan and offset detector data for cone-beam breast CT.. In Medical Physics 50-6, 2023 AAPM Meeting Program..
• Larsen, T. C., Tseng, H., Trinate, R., Fu, Z., Karellas, A., & Vedantham, S. (2023). Joint optimization of X-ray spectrum and scintillator thickness used in the detector for microcalcification detection in dedicated cone-beam breast CT.. In Medical Physics 50-6, 2023 AAPM Meeting Program.
• Reynolds, C., Renshaw, B., Vedantham, S., & Rogers, S. (2023). Utilizing DSC MR perfusion images for evaluation of hemorrhagic transformation after mechanical thrombectomy with Heidelberg grading and comparison to SWI, GRE, and CT.. In Journal of NeuroInterventional Surgery, 15 (Suppl 1), A14-A15.
• Trinate, R., Tseng, H., Larsen, T. C., Fu, Z., & Vedantham, S. (2023). Objective physics-based image quality characterization of a low-noise, high-resolution, dedicated cone-beam breast CT using an offset detector.. In Medical Physics 50-6, 2023 AAPM Annual Meeting Program, Abstract # SU-400-351-3.
• Tseng, H., Fu, Z., & Vedantham, S. (2023). Radiation dose reduction in cone-beam breast CT using shorter X-ray pulse-width with a self-supervised deep learning algorithm.. In Medical Physics 50-6, 2023 AAPM Annual Meeting Program.
• Tseng, H., Fu, Z., Chiang, J. A., Chow, H., & Vedantham, S. (2023). Patient-specific mean glandular dose from a high-resolution dedicated cone-beam breast CT system with offset detector.. In Medical Physics 50-6, 2023 AAPM Meeting Program.
• Vedantham, S., Tseng, H., Fu, Z., & Chow, H. (2023). Reproducibility of volumetric fibroglandular fraction in dedicated cone-beam breast CT.. In 2023 Program of the 10th International Breast Density & Cancer Risk Assessment Workshop, a10.
• Tseng, H., Karellas, A., & Vedantham, S. (2022).

  Angular normalized glandular dose coefficient in breast CT: clinical data study

  . In 7th International Conference on Image Formation in X-Ray Computed Tomography, 12304, 158-163.
• Shazeeb, M., Moholkar, V., King, R., Kuhn, A., Vedantham, S., Vardar, Z., Kraitem, A., Anagnostakou, V., Singh, J., Massari, F., de Macedo Rodrigues, K., Naragum, V., Puri, A., & Gounis, M. (2021, 06/Summer). Assessment of thrombectomy procedure difficulty by neurointerventionalists based on vessel geometry parameters from carotid artery 3D reconstructions. In 18th Annual Meeting of the Society of NeuroInterventional Surgery (SNIS), 13, A11-A11.
• Tseng, H., Karellas, A., & Vedantham, S. (2021, 07/Summer). Dedicated Cone-Beam Breast CT with Offset-Detector: Estimates of Mean Glandular Dose (MGD) with Heterogeneous Tissue Distribution and Real Breast Shapes from Clinical Datasets. In 63rd Annual Meeting of the American Association of Physicists in Medicine (AAPM), 48.
• Umapathy, L., Guzman Perez-Carillo, G., Winegar, B., Vedantham, S., Altbach, M., & Bilgin, A. (2021, 05/Spring). White matter hyperintensity volumes and cognition: Assessment of a deep learning-based lesion detection and quantification algorithm onADNI. In 2021 Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2021).
• Vedantham, S., Tseng, H., & Karellas, A. (2021, 07/Summer). Image Quality Evaluation of a Compressed-Sensing Algorithm for Image Reconstruction in Dedicated Cone-Beam Breast CT Using Offset-Detector. In 63rd Annual Meeting of the American Association of Physicists in Medicine (AAPM), 48.
• Jaffer, F., Chan, Y., Kumar, S., Parbtani, R., Vedantham, S., & Malo, J. (2020, May). High Risk Findings on Low Dose CT in a Coccidioidomycosis Endemic Area. In American Thoracic Society, Am J Respir Crit Care Med, A5938.
• Malo, J., Vedantham, S., Kumar, S., Jaffer, F., Chan, Y., Rao, S., & Parbtani, R. (2020, May). High Risk Findings on Low Dose CT in a Coccidioidomycosis Endemic Area. In American Thoracic Society (abstract in Am J Crit Care Med), 201, A5938.
• Vedantham, S., & Karellas, A. (2017, July). Dedicated breast CT: Numerical evaluation of improvement in x-ray fluence uniformity using 3D beam-shaping x-ray filter.. In 59th Annual Meeting of the AAPM, Medical Physics 44-6, 2017 AAPM Annual Meeting Program, 3177.
• Vedantham, S., & Karellas, A. (2017, Sep). Scintillator performance considerations for dedicated breast computed tomography. In Radiation Detectors in Medicine, Industry, and National Security XVIII, SPIE, Proc. SPIE 10393, 103930M (7 pages).
• Vedantham, S., Shrestha, S., Karellas, A., & Cho, S. H. (2017, Sep). A framework for optimizing micro-CT in dual-modality micro-CT/XFCT small-animal imaging system. In Radiation Detectors in Medicine, Industry, and National Security XVIII, SPIE, Proc. SPIE 10393, 103930R.
• Marosfoi, M., Langan, E., Vedantham, S., Clarencon, F., King, R., Wainwright, J., Gounis, M. J., & Puri, A. (2016, July). Acute thrombus formation on flow diverters imaged in vivo using optical coherence tomography. In 13th Annual Meeting SNIS, J NeuroIntervent Surg 8: Suppl 1, A19-A20.
• Marya, N. B., Shrestha, S., Vedantham, S., Patel, K., Rupawala, A. H., Aldrugh, S., Karam, A. R., Zacharias, I., & Karellas, A. (2016, APR). Radiomics of Computed Tomography (CT) Liver Scans: A Novel Method to Evaluate Liver Cirrhosis and Steatosis. In GASTROENTEROLOGY, 150, S1166-S1167.
• Shi, L., Vedantham, S., Karellas, A., & Zhu, L. (2016, February). Library-based scatter correction for dedicated cone beam breast CT: a feasibility study. In MEDICAL IMAGING 2016: PHYSICS OF MEDICAL IMAGING, 9783.
• Shi, L., Vedantham, S., Karellas, A., & Zhu, L. (2016, JUN). Library-Based X-Ray Scatter Correction for Dedicated Cone-Beam Breast CT: Clinical Validation. In MEDICAL PHYSICS, 43.
• Shi, L., Vedantham, S., Karellas, A., & Zhu, L. (2016, JUN). Scatter Correction for Dedicated Cone Beam Breast CT Based On a Forward Projection Model. In MEDICAL PHYSICS, 43, 3820-+.
• Shrestha, S., Vedantham, S., & Karellas, A. (2016, JUN). Alternative K-Edge Filters for Low-Energy Image Acquisition in Contrast Enhanced Spectral Mammography. In MEDICAL PHYSICS, 43, 3716-+.
• Shrestha, S., Vedantham, S., & Karellas, A. (2016, JUN). Towards Standardization of X-Ray Filters in Digital Mammography-Enabled Breast Tomosynthesis Systems. In MEDICAL PHYSICS, 43.
• Vedantham, S., Shrestha, S., Shi, L., Vijayaraghavan, G., & Karellas, A. (2016, JUN). Task-Specific Optimization of Scintillator Thickness for CMOS-Detector Based Cone-Beam Breast CT. In MEDICAL PHYSICS, 43, 3346-3346.
• Shi, L., Vedantham, S., & Karellas, A. (2015, JUN). Dedicated Cone-Beam Breast CT with Laterally-Shifted Detector: Monte Carlo Evaluation of X-Ray Scatter Distribution and Scatter-To-Primary Ratio. In MEDICAL PHYSICS, 42, 3682-3682.
• Shrestha, S., Vedantham, S., Karellas, A., Bellazzini, R., Spandre, G., & Brez, A. (2015, JUN). Photon-Counting Hexagonal Pixel Array CdTe Detector: Optimal Resampling to Square Pixels. In MEDICAL PHYSICS, 42, 3694-3694.
• Vedantham, S., Shi, L., & Karellas, A. (2015, JUN). Dedicated Cone-Beam Breast CT: Design of a 3-D Beam-Shaping Filter. In MEDICAL PHYSICS, 42, 3612-3612.
• Vedantham, S., Shi, L., Karellas, A., & O'Connell, A. (2015, JUN). Accuracy of Radiologists Interpretation of Mammographic Breast Density. In MEDICAL PHYSICS, 42, 3574-3575.
• Vedantham, S., Shi, L., Karellas, A., Michaelsen, K. E., Krishnaswamy, V., Pogue, B. W., & Paulsen, K. D. (2011, AUG). Semi-automated Segmentation and Classification of Digital Breast Tomosynthesis Reconstructed Images. In 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC), 6188-6191.
• Chowdhury, S. M., Vedantham, S., Suryanarayanan, S., Sumrain, S., Shah, N., Medithe, A., Kumar, V., Guntupalli, R., Giakos, G. C., Endorf, R. E., & Chowdhury, S. (2003). An efficient collector architecture for digital radiographic imaging czt semiconductor sensors. In Proceedings of the 20th IEEE Instrumentation Technology Conference (Cat. No.03CH37412), 1, 541-544.
• Nagarkar, V. V., Tipnis, S. V., Gaysinskiy, V. B., Miller SR, ., Karellas, A., & Vedantham, S. (2003, FEB). New design of a structured CsI(Tl) screen for digital mammography. In MEDICAL IMAGING 2003: PHYSICS OF MEDICAL IMAGING, PTS 1 AND 2, 5030, 541-546.
• Vedantham, S., Ved, H., Suryanarayanan, S., Karellas, A., & D'orsi, C. J. (2003). Evaluation of detection in compressed digital mammograms using numerical observers. In Medical Imaging 2003: Image Perception, Observer Performance, and Technology Assessment, 5034, 513-521.
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  The objective of this study was to evaluate an image compression technique for digital mammography using a nonprewhitening matched filter with an eye filter (NPWE) and channelized Hotelling numerical observer models. A total of 1024 images were cropped from clinical digital mammograms and used as backgrounds. The images were acquired using a clinical full-field digital mammography (FFDM) system and masses of sizes 30, 40, and 60 pixels (100 μm pixel size) were simulated. In addition, microcalcifications were synthetically extracted from clinical digital mammograms and used in the study. Image compression was achieved using a compression software (JPEG 2000, Aware Inc., Bedford, MA) at compression ratios 1:1, 15:1 and 30:1. The channelized Hotelling observer model was investigated only for the mass type lesions by transforming the images to channel space and computing the Hotelling trace for each compression condition. The NPWE model was investigated for both lesions and micocalcifications at all compression conditions and the detection indices were computed by assuming Gaussian statistics and by the 'percent correct’ detection method. The results of the study indicated a reduction in detection with increased compression for microcalcifications at 30:1 compression while almost no variation in detection index was observed for the simulated masses.
• Vedantham, S., Ved, H., Suryanarayanan, S., Karellas, A., & D'orsi, C. J. (2003). Theoretical and empirical characterization of the physical characteristics of a clinical digital mammography system. In SPIE Proceedings, 5030, 929-938.
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  The physical performance characteristics of a clinical full-field digital mammography (FFDM) system were analyzed for different target/filter conditions using theoretical modeling and experimental measurements. The signal and noise propagation through the various stages of the FFDM system was simulated as a cascaded process and used to compute the frequency dependent detective quantum efficiency (DQE) of the system. The presampling modulation transfer function (MTF) of the system and the noise power spectra (NPS) of the system were measured under the different spectral conditions as used in the theoretical model at an exposure close to 10-mR from which corresponding DQEs were computed. The experimental zero frequency DQE after filtering the x-ray beam through 45-mm acrylic was estimated at 0.51, 0.48, and 0.46 for Mo/Mo, Mo/Rh, and Rh/Rh respectively. A good agreement between the theoretical and experimental results was observed. The clinical digital mammography system appears to exhibit favorable physical characteristics and similar models could be used to design and optimize other imaging systems.
• Vedatham, S., Vedantham, S., Suryanarayanan, S., Sunirain, S., Sumrain, S., Shah, N., Patnekar, N., Odogba, J., Moholkar, A., Mehta, K., Kumar, V., Guntupalli, R., Giakos, G. C., Endorf, R. E., & Chowdhury, S. (2003). Detective quantum efficiency [DQE(0)] of CZT semiconductor detectors for digital radiography. In Proceedings of the 20th IEEE Instrumentation Technology Conference (Cat. No.03CH37412), 53, 1479-1484.
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  In this paper, the detective quantum efficiency (DQE) of cadmium zinc telluride (CZT) detector samples for digital radiography has been measured. Specifically, this study is aimed at investigating the zero-frequency DQE(0) under different X-ray tube and detector parameters. The experimental results of this study indicate that the DQE(0) of the CZT samples is strongly dependent upon the irradiation geometry. This is attributed to the incomplete charge collection process, which can be further improved by controlling the purity of the samples and the contact type.
• Glick, S. J., Vedantham, S., & Karellas, A. (2002, FEB). Investigation of optimal kVp settings for CT mammography using a flat-panel imager. In MEDICAL IMAGING 2002: PHYSICS OF MEDICAL IMAGING, 4682, 392-402.
• Vedantham, S., Suryanarayanan, S., Sumrain, S., Shah, N., Patnekar, N., Mehta, K., Guntupalli, R., Giakos, G. C., & Chowdhury, S. (2002). Intrinsic sensitivity of CdZnTe semiconductors for digital radiographic imaging. In IMTC/2002. Proceedings of the 19th IEEE Instrumentation and Measurement Technology Conference (IEEE Cat. No.00CH37276), 1, 475-480.
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  The intrinsic sensitivity of Cd/sub 1-x/Zn/sub x/Te semiconductor detectors have been theoretically modeled and experimentally measured, within the X-ray diagnostic energy range. The purpose of this study is to optimize the detector signal parameters of these solid state ionization devices for digital imaging applications. The experimental results of this study indicate that Cd/sub 1-x/Zn/sub x/Te detectors exhibit good intrinsic sensitivity.
• Vedantham, S., Ved, H., Suryanarayanan, S., Karellas, A., & D'orsi, C. J. (2002). Screen film versus digital mammography: a perceptual analysis of postprocessed hard copy images. In SPIE Proceedings, 4686, 312-318.
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  In this investigation we studied the imaging characteristics of a mammographic screen-film (MinR-2000, Eastman Kodak Co.) and an amorphous-silicon flat-panel digital mammography system (Senographe 2000D, GE Medical Systems) based on information perception by human observers. The focus of the study was to utilize an effective means to estimate the contrast-detail characteristics of x-ray imaging systems at various threshold levels to evaluate system performance with reduced observer subjectivity. We obtained three images of a contrast-detail phantom (CDMAM, Nuclear Associates) with screen-film and three images with digital mammography under identical exposure conditions. The digital images were printed using dry film printer (DryView 8600, Eastman Kodak Co.) after being windowed/leveled appropriately by two experienced radiologists. Seven observers reviewed the images and 'proportion correct' detection data were computed for each observer. A psychophysical signal detection model that hypothesizes a continuous decision variable internal to the observer with Gaussian probability density functions was used to fit the experimental observer data. Projection data from the detection curves at 50%, 62.5%, and 75% threshold levels were used to generate contrast-detail diagrams. Digital mammography, on average, exhibited lower (better) threshold contrast-detail characteristics compared to screen-film mammography.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
• Evans, E. A., Vedantham, S., Suryanarayanan, S., Sumrain, S., Shah, N., Russo, F., Patnekar, N., Passerini, A. G., Mehta, K., Guntupalli, R., Giakos, G. C., Evans, E. A., Endorf, R. J., & Chowdhury, S. (2000). Contrast sensitivity and dynamic range measurements of CdZnTe semiconductors for direct type flat-panel imaging. In Proceedings of the 17th IEEE Instrumentation and Measurement Technology Conference [Cat. No. 00CH37066], 1, 375-379.
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  The contrast sensitivity and dynamic range of Cd/sub 1-x/Zn/sub x/Te semiconductor detectors have been measured within the X-ray diagnostic energy range, using a contrast sensitivity phantom. The aim of this study is to optimize the image quality parameters of these solid state-ionization devices for flat panel digital radiographic applications. The experimental results of this study indicate that Cd/sub 1-x/Zn/sub x/Te detectors have excellent contrast sensitivity response and large dynamic range.
• Vedantham, S., Suryanarayanan, S., Sumrain, S., Shah, N., Scheiber, C., Passerini, A. G., Mehya, K., Giakos, G. C., & Chowdhury, S. (2000). Dual-energy measurements utilizing a novel multimedia detector. In Proceedings of the 17th IEEE Instrumentation and Measurement Technology Conference [Cat. No. 00CH37066], 2, 607-610.
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  Dual-energy measurements are presented utilizing a novel slot-scan digital radiographic imaging detector, operating on gaseous-solid state ionization principles. The novel multimedia detector has two basic functional components: a noble gas filled detector volume operating on gas microstrip principles, and a solid state detector volume. The purpose of this study is to investigate the potential use of this multimedia detector for enhanced dual-energy imaging. The experimental results indicate that the multimedia detector exhibits a high sensitivity. Although the intrinsic merit of this device is being explored for medical imaging, potential applications of the multimedia detector technology in other industrial areas are also very promising.
• Vedantham, S., Suryanarayanan, S., Sumrain, S., Sridhar, M., Shah, N., Russo, F., Patnekar, N., Passerini, A. G., Odogba, J., Nemer, R., Mehta, K., Guntupalli, R., Giakos, G. C., & Chowdhury, S. (2000). Pulse timing optimization of II-IV direct type semiconductor detectors for flat-panel pulsed X-ray imaging. In Proceedings of the 17th IEEE Instrumentation and Measurement Technology Conference [Cat. No. 00CH37066], 3, 1248-1252.
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  The rising and falling edges of detected signal pulses have been measured utilizing X-ray ionization of a planar Cd/sub 1-x/Zn/sub x/Te system under different irradiation geometries. The experimental results of this study indicate that the time response of the CdZnTe based X-ray system is suitable for digital pulsed radiographic applications.
• Vedantham, S., Pillai, B., Guntupalli, R. K., Giakos, G. C., & Chowdhury, S. (1998). A computed tomographic CdZnTe based scanning detector. In IMTC/98 Conference Proceedings. IEEE Instrumentation and Measurement Technology Conference. Where Instrumentation is Going (Cat. No.98CH36222), 1, 462-465.
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  In this feasibility study, single detector experiments were carried out in order to study the system characteristics of a cadmium zinc telluride (Cd/sub 1-x/Zn/sub x/Te) sample for pulsed X-ray computed tomography (CT). The experimental observations indicate the presence of long trailing edges which may be associated with charge trapping and recombination. On the other hand the system exhibits high stability.
• Vedantham, S., Suryanarayanan, S., Pillai, B., Odogba, J., Guntupalli, R. K., Giakos, G. C., Endorf, R. J., Dasgupta, A., & Chowdhury, S. (1998). Detection characterization of Cd1-xZnxTe detectors for x-ray linear arrays. In SPIE Proceedings, 3336, 537-545.
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  In this paper, the detected signal-to-noise was measured and related to the tube current (mA) setting. The line spread function amplitude (LSF) dependence on drift distance of a 3 mm thick detector, for 100 kVp, 100 mA, with an applied electric field of 50 V/mm, and 100 V/mm, were measured. In addition, the dependence of the modulation transfer function [MTF(f)] of the x-ray detector system on the applied bias voltage has been experimentally determined. The experimental setup, although is not offered for large field-of-view imaging applications, offers capabilities for feasibility studies, research and evaluation of the temporal response and noise characteristics of a Cd 1-x Zn x Te detector, for fast digital radiographic and CT applications. The experimental results indicate that Cd 1-x Zn x Te detectors exhibit both a high signal-to-noise ratio and linear response, as well as a good spatial resolution within the diagnostic energy range. Tor system improves both with increasing applied bias voltage and decreasing detector thickness. A study is in process aimed at improving the spatial resolution of the x-ray system by suitable optimization of the system geometry as well as the system temporal response.
• Vega-lozada, V., Vedantham, S., Suryanarayanan, S., Pillai, B., Odogba, M., Guntupalli, R., Giakos, G. C., Dasgupta, A., & Chowdhury, S. (1998). Modulation transfer function (MTF) measurement of CdZnTe detectors for digital radiography and computed tomography. In IMTC/98 Conference Proceedings. IEEE Instrumentation and Measurement Technology Conference. Where Instrumentation is Going (Cat. No.98CH36222), 1, 456-461.
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  In this study, dependence of the temporal modulation of a Cd/sub 1-x/Zn/sub x/Te detector, operated under scanning beam geometry, of both the applied electric field and detector thickness, at each frequency of a scanning square-wave test pattern, have been measured. The experimental arrangement, although is not offered for large field-of-view imaging applications, offers potential capabilities for feasibility studies, research and evaluation of the temporal response and noise characteristics of a Cd/sub 1-x/Zn/sub x/Te detector, for fast digital radiographic and computed tomographic (CT) applications. The experimental results indicate a system spatial resolution of >8 cy/mm. Currently, efforts are aimed at improving the imaging potential of the experimental detector system, by optimizing system geometry as well as by increasing the temporal response of the overall system.
• Vega-lozada, V., Vedantham, S., Suryanarayanan, S., Sheffer, D. B., Pillai, B., Odogba, J., Guntupalli, R., Giakos, G. C., & Chowdhury, S. (1998). Image analysis of CdZnTe detectors for digital radiography. In IMTC/98 Conference Proceedings. IEEE Instrumentation and Measurement Technology Conference. Where Instrumentation is Going (Cat. No.98CH36222), 1, 358-363.
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  In this study, the temporal response of a planar Cd/sub 1-x/Zn/sub x/Te sample at each frequency of a scanning square-wave test pattern, have been measured. The experimental arrangement, although is not offered for large field-of-view imaging applications, offers potential capabilities for feasibility studies, research and evaluation of the temporal response and noise characteristics of a Cd/sub 1-x/Zn/sub x/Te detector, for fast digital radiographic and CT applications. The dependence of the modulation transfer function (MTF(f)) of the experimental X-ray detector system of both the applied electric fields and thickness has been determined experimentally. The results of this study indicate that the overall MTF(f) of the CdZnTe detector system improves both with increasing applied bias voltage and decreasing detector thickness. Further improvement of the geometrical and signal collection parameters will improve the spatial resolution of the X-ray system significantly.
• Giakos, G. C., Chowdhury, S., Vedantham, S., Dasgupta, A., Pillai, B., Ghotra, P., Suryanarayanan, S., & Odogba, J. (1997, FEB). Feasibility study of a gas microstrip detector for medical applications. In PHYSICS OF MEDICAL IMAGING - MEDICAL IMAGING 1997, 3032, 459-468.
• Giakos, G. C., Vedantham, S., Chowdhury, S., & Pillai, B. (1997, FEB). Novel hybrid imaging modalities. In PHYSICS OF MEDICAL IMAGING - MEDICAL IMAGING 1997, 3032, 476-487.
• Vedantham, S., Odogba, J., & Giakos, G. C. (1997). Collection efficiency of CdZnTe detectors. In IEEE Instrumentation and Measurement Technology Conference Sensing, Processing, Networking. IMTC Proceedings, 1, 8-11.
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  In this work, the detection of signal charge produced by X-rays incident on resistive CdZnTe semiconductor substrates, at different detector geometries, within the X-ray diagnostic energy range, is investigated. The experimental results suggest that the observed signal-to-noise ratio is dependent upon the choice of the polarizing electrode that is directly exposed to the incident X-ray beam. An efficient charge defection is achieved achieved when the X-ray beam is incident on the negative electrode with the electric field parallel to the direction of the incoming photons.
• Vedantham, S., Pillai, B., Giakos, G. C., Ghotra, P., Dasgupta, A., & Chowdhury, S. (1997). Electrical characterization of CdZnTe imaging detectors for digital radiography. In SPIE Proceedings, 3032, 499-505.
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  Abstract The purpose of this study is to measure the electrical parameters of the Cd1ZnTe detectors, with the aim of characterizing the optimal detector performance parameters for digital radiographic applications. 1. Introduction Recent developments in digital technology have resulted in increased interest in semiconductor devices forradiological applications[1]-[3]. This paper describes some of our ongoing work in the application of the semiconductor material, Cd1ZnTe, for radiological uses. This material has high stopping power due to its highmass density (5.8 gm/cm3) and effective atomic number Z of 49.6 (Cd09:48, Zn1 :30, Te:52). It is important to make observations of its leakage current and capacitance at several voltages over the operating range to determine the noise performance ofthe system. It is also important to measure the resistivity of material so thatthe impedance can be matched to the input impedance of amplifier. The noise characteristics of Cdi..ZnTe aredescribed by measuring the variations of leakage current and capacitance with respect to parameters like biasvoltage and gain ofthe system.
• Vedantham, S., Richardson, D. B., Pillai, B., Passalaqua, A. M., Odogba, J., Giakos, G. C., Ghotra, P., Endorf, R. J., Dasgupta, A., & Chowdhury, S. (1997). Evaluation of a gas-microstrip dual-energy system. In SPIE Proceedings, 3032, 488-498.
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  The use of a gas microstrip detector in dual-energy radiography for certain clinical applications is explored. Optimal conditions of this technology for digital chest radiography are presented. These optimal conditions were obtained via computer simulations. The gas microstrip detector shows promise for achieving high spatial resolution, high internal gain, low noise and through the use of dual-energy techniques, high contrast resolution.
• Vedantham, S., Suryanarayanan, S., Richardson, D. B., Pillai, B., Passalaqua, A. M., Guntupalli, R. K., Giakos, G. C., Ghotra, P. S., Endorf, R. J., Dasgupta, A., & Chowdhury, S. (1997). Evaluation of a CdZnTe dual-energy system. In SPIE Proceedings, 3032, 469-475.
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  The purpose of the study is to optimize the input and the output parameters of a dual energy CdZnTe semiconductor detector for chest radiography. The optimal detector parameters were obtained by maximizing the figure of merit, defined as the ratio between the square of the signal-to- noise ratio and the absorbed dose, for chest radiography.
• Giakos, G. C., Chowdhury, S., Pillai, B., Ghotra, P., Vedantham, S., & Dasgupta, A. (1996, FEB). Novel multimedia detectors for medical imaging. In PHYSICS OF MEDICAL IMAGING, 2708, 759-770.
• Vedantham, S., Pillai, B., Giakos, G. C., Ghotra, P., Endorf, R. J., Dibianca, F. A., Devidas, S., Dasgupta, A., & Chowdhury, S. (1996). Progress in gas detector technology for medical imaging research. In Medical Imaging 1996: Physics of Medical Imaging, 2708, 771-780.
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  The x-ray capture, conversion into charge carriers, ion transport mechanisms and image formation mechanisms within a high-gas pressure digital radiographic system, operating up to 60 atm., are presented and analyzed. In detail, the physics of the high-pressure KCD imaging detectors is exposed, analyzed and related to the detector and image quality parameters. Specifically, this study indicates that ion diffusion cannot account for all the experimental observations. It advances the hypothesis that, at sufficiently high pressures, formation of molecular clusters with narrowed mobility distribution take place, through energy exchange mechanism, with local potential forces such that they compensate the space charge distortion of the applied field strength.

Presentations

• Duhancioglu, G., Gupta, K., Reynolds, C., Vedantham, S., & Arif Tiwari, H. (2023, April). Multiparametric MRI characterization for diagnosing acute cholecystitis.. 2023 American Roentgen Ray Society (ARRS) Annual Meeting.
• Fu, Z., Tseng, H., & Vedantham, S. (2023). An attenuation field network for cone-beam breast CT with a laterally-shifted detector in short scan.. 17th International Meeting on Fully 3D image reconstruction in Radiology and Nuclear medicine.
• Greenhill, M., Rounseville, B., Elcic, L., Trujillo, M., Vedantham, S., & Arif Tiwari, H. (2023, April). Implementation of an abbreviated venous duplex ultrasound protocol for detection of deep vein thrombus in hospitalized COVID-19 (+) patients. Annual Meeting of the American Roentgen Ray Society (ARRS 2023). Honolulu, HI: American Roentgen Ray Society.
• Rogers, S., Renshaw, B., Reynolds, C. A., Frazzitta, A., Bhandari, A., & Vedantham, S. (2023, April). Validating Heildelberg ratings of hemorrhagic transformation after mechanical thrombectomy on MRI with SWI and GRE sequences, with comparison to CT. Annual Meeting of the American Society of Neuroradiology (ASNR 2023). Chicago, IL: American Society of Neuroradiology.
• Rogers, S., Reynolds, C. A., Frazzitta, A., Renshaw, B., Bhandari, A., & Vedantham, S. (2023, April). Contrast-enhanced FLAIR and the relationship to hemorrhagic transformation in patients with large vessel occlusion treated with mechanical thrombectoy. Annual Meeting of the American Society of Neuroradiology 2023 (ASNR 2023). Chicago, IL: American Society of Neuroradiology.
• Vedantham, S. (2023). Advanced breast CT and quantitative breast cancer assessment.. National Cancer Institute, Quantitative Imaging Working Group.
• A, B., Vedantham, S., Rogers, S., Mushtaq, R., & R, W. J. (2022). Imaging Characteristics of Hyperostosis Frontalis Interna.. 54th Annual Meeting of the Western Neuroradiology Society. Indian Wells, CA: Western Neuroradiology Society.
• D, C., J, L., Vedantham, S., Kubal, W. S., & Mushtaq, R. (2022). Temporal enhancement pattern between Cavernous Sinus and Suboccipital Cavernous Sinus: Results from analysis of MRI data.. 54th Annual Meeting of the Western Neuroradiology Society. Indian Wells, CA: Western Neuroradiology Society.
• Di Maria, S., Vedantham, S., & Vaz, P. (2022, October). X-ray dosimetry in breast cancer screening: state-of-the-art and emerging technologies. European Radiation Protection Week (ERPW 2022). Estoril (Lisbon), Portugal.
• Fu, Z., Tseng, H., Karellas, A., & Vedantham, S. (2022). Dedicated Breast CT Image Reconstruction: Self-supervised Denoising from Single Image. 2022 University of Arizona College of Medicine Research Day. Tucson, AZ.
• J, L., D, C., Vedantham, S., Kubal, W. S., & Mushtaq, R. (2022). Quantitative association between CS and SCS enhancement: Results from analysis of CT data. . 54th Annual Meeting of the Western Neuroradiology Society. Indian Wells, CA: Western Neuroradiology Society.
• Tseng, H., Karellas, A., & Vedantham, S. (2022). Angular Normalized Dose Coefficients in Breast CT: Clinical data study.. University of Arizona College of Medicine Research Day. Tucson, AZ.
• Vedantham, S. (2021, 08/Fall). Towards breast cancer screening with dedicated breast computed tomography (CT). University of Arizona Cancer Center Collaborative Grand Rounds. Tucson, AZ: University of Arizona Cancer Center (UACC).
• Vedantham, S. (2021, 09/Fall). Screening for Breast Cancer with Dedicated Breast Computed Tomography. Biomedical Engineering Seminar, Rennselaer Polytechnic InstituteRennselaer Polytechnic Institute.
• Vedantham, S. (2021, 11/Fall). Breast cancer screening with dedicated breast computed tomography: Challenges and Opportunities. Research Seminar, Department of Radiological Sciences, University of California at Irvine (UCI)University of California at Irvine (UCI).
• Fu, Z., Tseng, H., Vedantham, S., Karellas, A., & Bilgin, A. (2020, July). Dedicated Breast CT: Comparative Evaluation of Multi-Scale Residual Dense Network and Residual Encoder-Decoder Network for Deep Learning-Driven Sparse-View Reconstruction. American Association of Physicists in Medicine (AAPM) Annual Meeting. Vancouver, Canada (Virtual): American Association of Physicists in Medicine.
• Spicer, C., Vedantham, S., Kalb, B. T., & Arif Tiwari, H. (2020, March). Diagnostic Performance of MR Imaging in the Detection of Ovarian Torsion. SAR 2020 Annual Scientific Meeting and Educational Course. Maui, HI: Society of Abdominal Radiology.
• Tseng, H., Vedantham, S., & Karellas, A. (2020, July). Upright Dedicated Cone-Beam Breast CT: Short-Scan, Non-Uniform, Sparse-View Angular Sampling for Radiation Dose Reduction. American Association of Physicists in Medicine (AAPM) Annual Meeting. Vancouver, Canada (Virtual): American Association of Physicists in Medicine (AAPM).
• Tseng, H., Vedantham, S., & Karellas, A. (2020, November). Short-scan, non-uniform, sparse-view angular sampling for radiation dose reduction in upright dedicated breast CT. University of Arizona Cancer Center (UACC) Retreat. Tucson, AZ: University of Arizona Cancer Center (UACC).
• Vedantham, S. (2020, December). Advanced X-ray and Tomographic Imaging. University of Arizona, DMI Research Division Workshop. Tucson, AZ: Department of Medical Imaging (DMI), University of Arizona.
• Vedantham, S., Udayasankar, U., Sawyer, D., & Mushtaq, R. (2020, May). Accuracy of Resident and Attending radiologist interpretations of abdominopelvic magnetic resonance imaging performed for pediatric acute appendicitis. SPR 2020 Annual Meeting & Postgraduate Course. Miami, FL (virtual): Society of Pediatric Radiology.
• Arif Tiwari, H., & Vedantham, S. (2019, June/Summer). Advances in Multiparametric MRI and Fusion Prostate Biopsy for Prostate Adenocarcinoma: A Changing Paradigm.. Prostate Cancer Working Group Annual Meeting, University of Arizona Cancer Center. Tucson, AZ: University of Arizona Cancer Center.
• Fu, Z., Tseng, H., Vedantham, S., Karellas, A., & Bilgin, A. (2019, Dec/Fall). Deep Learning-Driven Sparse-View Reconstruction for Radiation Dose Reduction in Dedicated Breast CT: Quantitative Evaluation.. 105th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA), 2019 RSNA Annual Meeting Program, Abstract # SSC13-05.. Chicago, IL: Radiological Society of North America (RSNA).
• Spicer, C., Spicer, C., Kalb, B. T., Kalb, B. T., Martin, D. R., Martin, D. R., Vedantham, S., Vedantham, S., Arif Tiwari, H., & Arif Tiwari, H. (2019, May). Diagnostic accuracy of shear-wave elastography combined with standard ultrasound imaging in thyroid nodule evaluation.. Annual Meeting of the American Roentgen Ray Society (ARRS 2019). Honolulu, HI: American Roentgen Ray Society (ARRS 2019).
• Tseng, H., Vedantham, S., & Karellas, A. (2019, February). Radiation dose reduction in dedicated breast computed tomography.. 2019 University of Arizona College of Medicine Research Day. Tucson, AZ: University of Arizona, College of Medicine.
• Tseng, H., Vedantham, S., & Karellas, A. (2019, February). System design in X-ray Fluorescence Computed Tomography (XFCT) using analytical point spread function system matrix.. 2019 University of Arizona College of Medicine Research Day. Tucson, AZ: University of Arizona, College of Medicine.
• Tseng, H., Vedantham, S., Cho, S., & Karellas, A. (2019, Aug 2019). Expedient System Optimization of X-Ray Fluorescence Computed Tomography (XFCT) Using Analytical Point Spread Function and Model Observer. 61st Annual Meeting of the American Association of Physicists in Medicine (AAPM), MEDICAL PHYSICS 46 (6), E191-E191. San Antonio, TX: American Association of Physicists in Medicine (AAPM).
• Vedantham, S. (2019, April/Spring). Quantitative Whole-breast X-ray Imaging. Cancer Prevention & Control (CPC)/Cancer Imaging Program (CIP) Joint Retreat, University of Arizona Cancer Center. Tucson, AZ: University of Arizona Cancer Center.
• Vedantham, S. (2019, Sep 16). Beyond Tomosynthesis: Advancing Fully 3D, Quantitative, Breast Cancer X-ray Imaging. BME Seminar Series. Tucson, AZ: Department of Biomedical Engineering, University of Arizona.
• Vedantham, S. (2019, Sep 2019). Quantitative measurement of breast density. Cancer Prevention and Control Seminar, University of Arizona Cancer Center. Tucson, AZ: University of Arizona Cancer Center.
• Vedantham, S., & Karellas, A. (2019, February). Automated notification: Radiomics of non-contrast CT scans.. 2019 University of Arizona College of Medicine Research Day. Tucson, AZ: University of Arizona College of Medicine.
• Vedantham, S., & Karellas, A. (2019, February). Interventional Radiology: Dual-energy dynamic imaging.. 2019 University of Arizona College of Medicine Research Day. Tucson, AZ: University of Arizona, College of Medicine.
• Arif, H., Kalb, B., Funk, J., Cress, A., Vedantham, S., & Martin, D. R. (2018, March). Magnetic Resonance-directed Ultrasound-guided (MRdUSg) prostate biopsies using a new real-time registration and image display system to improve tumor-targeting accuracy. Annual Scientific Meeting and Educational Course, Society of Abdominal Radiology, 2018. Scottsdale, Arizona: Society of Abdominal Radiology.
• Bhowra, A., Petkovska, I., Martin, D. R., Kalb, B. T., & Vedantham, S. (2018, JUN). The Diagnostic Accuracy of MR Imaging for Acute Pyelonephritis. Joint Annual Meeting ISMRM-ESMRMB 2018. Paris, France: ISMRM.
• Desoky, S. M., Arteaga, V., Vedantham, S., & Taljanovic, M. S. (2018, May). Comparison of Assessment of Medical Student Knowledge Following a Radiology Rotation by Radiology ExamWeb and Institutionally-created Final Examinations: Are the Exams Comparable and Does a Subspecialty Rotation Make a Difference in Performance?. 66th Annual Meeting of the Association of University Radiologists (AUR). Orlando, FL: Association of University Radiologists (AUR).
• Tseng, H., Vedantham, S., & Karellas, A. (2018, Summer). Dedicated Breast CT: Impact of Short-Scan Source Trajectory and Sparse-View Acquisition on Image Quality. 60th Annual Meeting of the American Association of Physicists in Medicine (AAPM), Medical Physics 45 (6), E479-E480. Nashville, TN: AAPM.
• Tseng, H., Vedantham, S., & Karellas, A. (2018, Summer). Impact of GPU-Accelerated Sparse-View Reconstruction for Radiation Dose Reduction in Dedicated Breast CT. 60th Annual Meeting of the American Association of Physicists in Medicine (AAPM), Medical Physics 45 (6), E555-E555. Nashville, TN: AAPM.
• Vedantham, S. (2018, July). Let There Be Light! Photon Counting Detectors as the Next Step. 15th Annual Meeting of the Society of NeuroInterventional Surgery (SNIS 2018). San Francisco, CA: SNIS.
• Vedantham, S. (2018, March). Advances in 3D X-ray Breast Imaging. Cancer Imaging Program Meeting. University of Arizona Cancer Center.
• Litchman, J., Chueh, J. Y., Arslanian, R., Vedantham, S., Carniato, S., Rex, D. E., Howk, M., Gounis, M. J., & Puri, A. S. (2017, Spring). Clot characterization in acute ischemic stroke.. 2017 UMass Center for Clinical and Translational Science Research Retreat. Worcester, MA: UMass Medical School.
• Santos-Nunez, G. A., Kipervasser, E., Vedantham, S., Dundamadappa, S. K., & Takhtani, D. (2017, Dec). Presence of temporal lobe lesions help differentiate multiple sclerosis from small vessel ischemic changes.. 103rd Scientific Assembly and Annual Meeting of the Radiological Society of North America, 2017 RSNA Annual Meeting Program. Chicago, IL: Radiological Society of North America (RSNA).
• Vedantham, S. (2017, Apr). Towards breast cancer screening with dedicated breast computed tomography.. Arizona Research Institute for Biomedical Imaging Spring Workshop. Tucson, AZ: University of Arizona.
• Vedantham, S. (2017, Dec). X-ray imaging of the breast in 3D. 103rd Scientific Assembly and Annual Meeting of the Radiological Society of North America, 2017 RSNA Annual Meeting Program. Chicago, IL: Radiological Society of North America (RSNA).
• Vedantham, S. (2017, Oct). BIG-CT: Overview of research opportunities.. Medical Imaging Grand Rounds, University of Arizona. Tucson, AZ.
• Vedantham, S. (2016, JUN). Introduction to Dedicated Breast CT - Early Studies. MEDICAL PHYSICS.
• Karellas, A., Molloi, S., Zhou, O., Zhao, W., & Vedantham, S. (2015, JUN). Advances in Breast Imaging. MEDICAL PHYSICS.

Poster Presentations

• Larsen, T. C., Tseng, H., Trinate, R., Fu, Z., & Vedantham, S. (2023, February). Maximizing microcalcification detectability in low dose dedicated cone beam breast CT: Parallel cascades-based theoretical analysis. 11th Annual BME Research Expo. University of Arizona.
• Larsen, T. C., Tseng, H., Trinate, R., Fu, Z., Karellas, A., & Vedantham, S. (2023). Joint optimization of scintillator thickness and x-ray spectrum for microcalcification detection in dedicated cone-beam breast CT.. American Physician Scientists Assocation (APSA) 2023 Joint Meeting. Chicago, IL.
• Trinate, R., Tseng, H., Larsen, T. C., Fu, Z., & Vedantham, S. (2023, February). Quantitative evaluation of image quality for dedicated cone-beam computerized tomography. 11th Annual BME Research Expo. University of Arizona.
• Fu, Z., Tseng, H., Karellas, A., & Vedantham, S. (2022).

  A Self-supervised Pseudo-3D Network for Cone-beam Dedicated Breast CT Denoising.

  . The University of Arizona Cancer Center’s Annual Scientific Retreat 2022. Tucson, AZ: University of Arizona Cancer Center.
• Tseng, H., Fu, Z., Karellas, A., & Vedantham, S. (2022). Radiation dose reduction for the dedicated breast CT using shorter x-ray pulse width and model-based iterative reconstruction algorithm.. The University of Arizona Cancer Center’s Annual Scientific Retreat 2022. Tucson, AZ: University of Arizona Cancer Center.
• Tseng, H., Vedantham, S., & Karellas, A. (2019, Aug 2019). Impact of Uniform and Nonuniform Angular Sampling in Short-Scan Dedicated Breast Computed Tomography. 61st Annual Meeting of the American Association of Physicists in Medicine (AAPM), MEDICAL PHYSICS 46 (6), E428-E428. San Antonio, TX: American Association of Physicists in Medicine (AAPM).