Maria I Altbach

Interests

Research

Dr. Altbach’s research group is focused on the development of novel magnetic resonance imaging (MRI) techniques for improving the diagnosis of disease. We develop novel acquisition and reconstruction strategies and we work closely with clinicians to translate them into the clinic. One of the major goals is to be able to derive parameters for the quantification of disease from data acquired within the time constraints of a clinical MRI examination. The idea is to complement the current qualitative-approach of clinical radiology with a quantitative or “parametric” approach. This should not only improve the accuracy in diagnosis but it should also allow radiologists to interpret data faster. One of the major goals is to develop acquisition and reconstructions strategies that can yield quantitative parameters for the characterization of disease.

Courses

Scholarly Contributions

Chapters

• Weinkauf, C., Trouard, T., Altbach, M., Tan, T., Zhou, W., Arias, J., Bernstein, A., Guzman, G., Bruck, D., Berman, S., Leon, L., Pacanowski, J., & Goshima, K. (2021). Improved Cognition and Preserved Hippocampal Fractional Anisotropy in Subjects Undergoing Carotid Endarterectomy. In Improved Cognition and Preserved Hippocampal Fractional Anisotropy in Subjects Undergoing Carotid Endarterectomy. Research Square Platform LLC. doi:10.21203/rs.3.rs-185232/v1
• Altbach, M. I. (2009). A Radial Magnetic Resonance Imaging Method for Imaging Abdominal Neoplasms. In Liver Cancer. Springer, Dordrecht. doi:10.1007/978-1-4020-9804-8_3

Journals/Publications

• Omar, I. M., Weaver, J. S., Altbach, M. I., Herynk, B. A., McCurdy, W. E., Kadakia, A. R., & Taljanovic, M. S. (2023). Imaging of osteoarthritis from the ankle through the midfoot. Skeletal radiology, 52(11), 2239-2257.
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  Ankle, hindfoot, and midfoot osteoarthritis (OA) is most commonly posttraumatic and tends to become symptomatic in younger patients. It often results from instability due to insufficiency of supportive soft tissue structures, such as ligaments and tendons. Diagnostic imaging can be helpful to detect and characterize the distribution of OA, and to assess the integrity of these supportive structures, which helps determine prognosis and guide treatment. However, the imaging findings associated with OA and instability may be subtle and unrecognized until the process is advanced, which may ultimately limit therapeutic options to salvage procedures. It is important to understand the abilities and limitations of various imaging modalities used to assess ankle, hindfoot, and midfoot OA, and to be familiar with the imaging findings of OA and instability patterns.
• Umapathy, L., Brown, T., Mushtaq, R., Greenhill, M., Lu, J., Martin, D., Altbach, M., & Bilgin, A. (2023). Reducing annotation burden in MR: A novel MR-contrast guided contrastive learning approach for image segmentation. Medical physics.
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  Contrastive learning, a successful form of representational learning, has shown promising results in pretraining deep learning (DL) models for downstream tasks. When working with limited annotation data, as in medical image segmentation tasks, learning domain-specific local representations can further improve the performance of DL models.
• Fu, Z., Johnson, K., Altbach, M. I., & Bilgin, A. (2022). Cancellation of streak artifacts in radial abdominal imaging using interference null space projection. Magnetic resonance in medicine, 88(3), 1355-1369.
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  In radial abdominal imaging, it has been commonly observed that signal from the arms cause streaks due to system imperfections. We previously introduced a streak removal technique (B-STAR), which is inherently spatially variant and limited to work in image space. In this work, we propose a spatially invariant streak cancellation technique (CACTUS), which can be applied in either image space or k-space and is compatible with iterative reconstructions.
• Keerthivasan, M. B., Galons, J. P., Johnson, K., Umapathy, L., Martin, D. R., Bilgin, A., & Altbach, M. I. (2021). Abdominal T2-Weighted Imaging and T2 Mapping Using a Variable Flip Angle Radial Turbo Spin-Echo Technique. Journal of magnetic resonance imaging : JMRI, 55(1), 289-300.
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  T2 mapping is of great interest in abdominal imaging but current methods are limited by low resolution, slice coverage, motion sensitivity, or lengthy acquisitions.
• 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 T 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.
• Tapia, E., Villa-Guillen, D. E., Chalasani, P., Centuori, S., Roe, D. J., Guillen-Rodriguez, J., Huang, C., Galons, J. P., Thomson, C. A., Altbach, M., Trujillo, J., Pinto, L., Martinez, J. A., Algotar, A. M., & Chow, H. S. (2021). A randomized controlled trial of metformin in women with components of metabolic syndrome: intervention feasibility and effects on adiposity and breast density. Breast cancer research and treatment, 190(1), 69-78.
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  Obesity is a known risk factor for post-menopausal breast cancer and may increase risk for triple negative breast cancer in premenopausal women. Intervention strategies are clearly needed to reduce obesity-associated breast cancer risk.
• Umapathy, L., Perez-Carrillo, G. G., Keerthivasan, M. B., Rosado-Toro, J. A., Altbach, M. I., Winegar, B., Weinkauf, C., Bilgin, A., & , A. D. (2021). A Stacked Generalization of 3D Orthogonal Deep Learning Convolutional Neural Networks for Improved Detection of White Matter Hyperintensities in 3D FLAIR Images. AJNR. American journal of neuroradiology, 42(4), 639-647.
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  Accurate and reliable detection of white matter hyperintensities and their volume quantification can provide valuable clinical information to assess neurologic disease progression. In this work, a stacked generalization ensemble of orthogonal 3D convolutional neural networks, StackGen-Net, is explored for improving automated detection of white matter hyperintensities in 3D T2-FLAIR images.
• Fu, Z., Mandava, S., Keerthivasan, M. B., Li, Z., Johnson, K., Martin, D. R., Altbach, M. I., & Bilgin, A. (2020). A multi-scale residual network for accelerated radial MR parameter mapping. Magnetic resonance imaging, 73, 152-162.
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  A deep learning MR parameter mapping framework which combines accelerated radial data acquisition with a multi-scale residual network (MS-ResNet) for image reconstruction is proposed. The proposed supervised learning strategy uses input image patches from multi-contrast images with radial undersampling artifacts and target image patches from artifact-free multi-contrast images. Subspace filtering is used during pre-processing to denoise input patches. For each anatomy and relaxation parameter, an individual network is trained. in vivo T mapping results are obtained on brain and abdomen datasets and in vivo T mapping results are obtained on brain and knee datasets. Quantitative results for the T mapping of the knee show that MS-ResNet trained using either fully sampled or undersampled data outperforms conventional model-based compressed sensing methods. This is significant because obtaining fully sampled training data is not possible in many applications. in vivo brain and abdomen results for T mapping and in vivo brain results for T mapping demonstrate that MS-ResNet yields contrast-weighted images and parameter maps that are comparable to those achieved by model-based iterative methods while offering two orders of magnitude reduction in reconstruction times. The proposed approach enables recovery of high-quality contrast-weighted images and parameter maps from highly accelerated radial data acquisitions. The rapid image reconstructions enabled by the proposed approach makes it a good candidate for routine clinical use.
• Mandava, S., Keerthivasan, M. B., Martin, D. R., Altbach, M. I., & Bilgin, A. (2021). Improving subspace constrained radial fast spin echo MRI using block matching driven non-local low rank regularization. Physics in medicine and biology.
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  Subspace-constrained reconstruction methods restrict the relaxation signals (of size M) in the scene to a pre-determined subspace (of size K≪M) and allow multi-contrast imaging and parameter mapping from accelerated acquisitions. However, these constraints yield poor image quality at some imaging contrasts, which can impact the parameter mapping performance. Additional regularization such as the use of joint-sparse (JS) or locally-low-rank (LLR) constraints can help improve the recovery of these images but are not sufficient when operating at high acceleration rates. We propose a method, non-local rank 3D (NLR3D), that is built on block matching and transform domain low rank constraints to allow high quality recovery of subspace-coefficient images and subsequent multi-contrast imaging and parameter mapping. The performance of NLR3D was evaluated using Monte-Carlo simulations and compared against the JS and LLR methods. In-vivo T2 mapping results are presented on brain and knee datasets. Monte-Carlo results demonstrate improved bias, variance, and MSE behavior in both the multi-contrast images and parameter maps when compared to the JS and LLR methods. In-vivo brain and knee results at moderate and high acceleration rates demonstrate improved recovery of high SNR early TE images as well as parameter maps. No significant difference was found in the T2 values measured in ROIs between the NLR3D reconstructions and the reference images (Wilcoxon signed rank test). The proposed method, NLR3D, enables recovery of high-quality subspace-coefficient images and, consequently, the associated multi-contrast images and parameter maps.
• Umapathy, L., Winegar, B., MacKinnon, L., Hill, M., Altbach, M. I., Miller, J. M., & Bilgin, A. (2020). Fully Automated Segmentation of Globes for Volume Quantification in CT Images of Orbits using Deep Learning. AJNR. American journal of neuroradiology, 41(6), 1061-1069.
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  Fast and accurate quantification of globe volumes in the event of an ocular trauma can provide clinicians with valuable diagnostic information. In this work, an automated workflow using a deep learning-based convolutional neural network is proposed for prediction of globe contours and their subsequent volume quantification in CT images of the orbits.
• Blew, R. M., Lee, V. R., Bea, J. W., Hetherington-Rauth, M. C., Galons, J. P., Altbach, M. I., Lohman, T. G., & Going, S. B. (2019). Validation of Peripheral Quantitative Computed Tomography-Derived Thigh Adipose Tissue Subcompartments in Young Girls Using a 3 T MRI Scanner. Journal of clinical densitometry : the official journal of the International Society for Clinical Densitometry, 21(4), 583-594.
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  The ability to assess skeletal muscle adipose tissue is important given the negative clinical implications associated with greater fat infiltration of the muscle. Computed tomography and magnetic resonance imaging (MRI) are highly accurate for measuring appendicular soft tissue and muscle composition, but have limitations. Peripheral quantitative computed tomography (pQCT) is an alternative that investigators find valuable because of its low radiation, fast scan time, and comparatively lower costs. The present investigation sought to assess the accuracy of pQCT-derived estimates of total, subcutaneous, skeletal muscle, intermuscular, and calculated intramuscular adipose tissue areas, and muscle density in the midthigh of young girls using the gold standard, 3 T MRI, as the criterion. Cross-sectional data were analyzed for 26 healthy girls aged 9-12 years. Midthigh soft tissue composition was assessed by both pQCT and 3 T MRI. Mean tissue area for corresponding adipose compartments by pQCT and MRI was compared using t tests, regression analysis, and Bland-Altman plots. Muscle density was regressed on MRI skeletal muscle adipose tissue, intermuscular adipose tissue, and intramuscular adipose tissue, each expressed as a percentage of total muscle area. Correlations were high between MRI and pQCT for total adipose tissue (r = 0.98), subcutaneous adipose tissue (r = 0.95), skeletal muscle adipose tissue (r = 0.83), and intermuscular adipose tissue (r = 0.82), and pQCT muscle density correlated well with both MRI skeletal muscle adipose tissue (r = 0.70) and MRI intermuscular adipose tissue (r = 0.70). There was a slight, but statistically significant underestimation by pQCT for total and subcutaneous adipose tissue, whereas no significant difference was observed for skeletal muscle adipose tissue. Both pQCT-estimated intramuscular adipose tissue and muscle density were weakly correlated with MRI-intramuscular adipose tissue. We conclude that pQCT is a valid measurement technique for estimating all adipose subcompartments, except for intramuscular adipose tissue, for the midthigh region in young/adolescent girls.
• Keerthivasan, M. B., Saranathan, M., Johnson, K., Fu, Z., Weinkauf, C. C., Martin, D. R., Bilgin, A., & Altbach, M. I. (2019). An efficient 3D stack-of-stars turbo spin echo pulse sequence for simultaneous T2-weighted imaging and T2 mapping. Magnetic resonance in medicine, 82(1), 326-341.
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  To design a pulse sequence for efficient 3D T2-weighted imaging and T2 mapping.
• Li, Z., Bilgin, A., Johnson, K., Galons, J. P., Vedantham, S., Martin, D. R., & Altbach, M. I. (2019). Rapid high-resolution T mapping using a highly accelerated radial steady-state free-precession technique. Journal of magnetic resonance imaging : JMRI, 49(1), 239-252.
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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.
• Mandava, S., Keerthivasan, M. B., Martin, D. R., Altbach, M. I., & Bilgin, A. (2019). Radial streak artifact reduction using phased array beamforming. Magnetic resonance in medicine, 81(6), 3915-3923.
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  A new method for streak artifact reduction in radial MRI based on phased array filtering.
• Blew, R., Lee, V., Bea, J. W., Hetherington-Rauth, M., Galons, J., Altbach, M. I., Lohman, T. G., & Going, S. B. (2018). Validation of Peripheral Quantitative Computed Tomography-Derived Thigh Adipose Tissue Subcompartments in Young Girls Using a 3 T MRI Scanner. Journal of Clinical Densitometry, 583-594.
• Ding, J., Stopeck, A. T., Gao, Y., Marron, M. T., Wertheim, B. C., Altbach, M. I., Galons, J. P., Roe, D. J., Wang, F., Maskarinec, G., Thomson, C. A., Thompson, P. A., & Huang, C. (2018). Reproducible automated breast density measure with no ionizing radiation using fat-water decomposition MRI. Journal of magnetic resonance imaging : JMRI, 48(4), 971-981.
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  Increased breast density is a significant independent risk factor for breast cancer, and recent studies show that this risk is modifiable. Hence, breast density measures sensitive to small changes are desired.
• Keerthivasan, M. B., Mandava, S., Johnson, K., Avery, R., Janardhanan, R., Martin, D. R., Bilgin, A., & Altbach, M. I. (2018). A multi-band double-inversion radial fast spin-echo technique for T2 cardiovascular magnetic resonance mapping of the heart. Journal of Cardiovascular Magnetic Resonance. doi:10.1186/s12968-018-0470
• Keerthivasan, M. B., Mandava, S., Johnson, K., Avery, R., Janardhanan, R., Martin, D. R., Bilgin, A., & Altbach, M. I. (2018). A multi-band double-inversion radial fast spin-echo technique for T2 cardiovascular magnetic resonance mapping of the heart. Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance, 20(1), 49.
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  Double inversion recovery (DIR) fast spin-echo (FSE) cardiovascular magnetic resonance (CMR) sequences are used clinically for black-blood T2-weighted imaging. However, these sequences suffer from slice inefficiency due to the non-selective inversion pulses. We propose a multi-band (MB) encoded DIR radial FSE (MB-DIR-RADFSE) technique to simultaneously excite two slices. This sequence has improved signal-to-noise ratio per unit time compared to a single slice excitation. It is also motion robust and enables the reconstruction of high-resolution black-blood T2-weighted images and T2 maps for the excited slices.
• Keerthivasan, M. B., Winegar, B., Becker, J. L., Bilgin, A., Altbach, M. I., & Saranathan, M. (2018). Clinical Utility of a Novel Ultrafast T2-Weighted Sequence for Spine Imaging. AJNR. American journal of neuroradiology, 39(8), 1568-1575.
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  TSE-based T2-weighted imaging of the spine has long scan times. This work proposes a fast imaging protocol using variable refocusing flip angles, optimized for blurring and specific absorption rate.
• Mandava, S., Keerthivasan, M. B., Li, Z., Martin, D. R., Altbach, M. I., & Bilgin, A. (2018). Accelerated MR parameter mapping with a union of local subspaces constraint. Magnetic resonance in medicine, 80(6), 2744-2758.
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  A new reconstruction method for multi-contrast imaging and parameter mapping based on a union of local subspaces constraint is presented.
• Galons, J., Stopeck, A., Marron, M. T., Wertheim, B. C., Wang, F., Thomson, C. A., Thompson, P. A., Stopeck, A., Roe, D. J., Maskarinec, G., Marron, M. T., Huang, C., Gao, Y., Galons, J., Ding, J., & Altbach, M. I. (2017). Abstract P3-02-03: Accurate and reliable automated breast density measurements with no ionizing radiation using fat-water decomposition MRI. Cancer Research, 77(4_Supplement), P3-02-03-P3-02-03. doi:10.1158/1538-7445.sabcs16-p3-02-03
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  Objective Breast density(BD) is a measure of the distribution of variable tissue types within the breast and higher BD has been shown to positively correlate with breast cancer risk. As such, the accurate measurement of BD has become a priority for risk assessment and for evaluating the effects of prevention strategies aimed at reducing BD. Mammography(MG) is the most common method of BD determination but is limited by the exposure to ionizing radiation, particularly for studies requiring repeated measures. BD derived from fat-water decomposition magnetic resonance imaging(FWMRI-BD) has been proposed as an alternative, safe, and quantitative method for BD. To optimize its use, we developed a new FWMRI-BD that is automated, more accurate and reliable. In this study, we compare our automated method to digital MG and a previous reported algorithm for MRI derived BD. Methods From a completed prevention trial, 42 pre- and post-menopausal patients receiving tamoxifen therapy for early stage breast cancer or as primary chemoprevention were identified. Patients had undergone prior digital MG within 6 months from the date of MRI scan and MG-BD was calculated using a well-established method(Cumulus). MRI scans were performed on a 1.5T GE Signa NV-CV/i scanner using an axial radial IDEAL-GRASE sequence to generate quantitative fat fraction maps of the entire breast. Total acquisition time was Results Table 1 shows the correlation and reliability analysis results between MG-BD and FWMRI-BD. Both FWMRI-BD measures(Fra80 and FraG+W) were strongly correlated with MG-BD. More importantly, they exhibit superior test-retest reliability(ICC>0.98) compared to MG-BD values from the literature(reported ICC range 0.91-0.95). FraG+W showed improvement over Fra80 in all measures tested including correlation to MG-BD, dynamic range, standard errors and ICC. Conclusion The refined and automated FWMRI-BD that quantifies the entire fibroglandular and water content of the breast(FraG+W) strongly correlates with MG-BD and is more accurate and reliable than previous FWMRI-BD method. Acknowledgement NIH grants CA149417, CA161534. Citation Format: Ding J, Thompson PA, Gao Y, Marron MT, Wertheim BC, Altbach MI, Galons J-P, Roe DJ, Wang F, Maskarinec G, Thomson CA, Stopeck A, Huang C. Accurate and reliable automated breast density measurements with no ionizing radiation using fat-water decomposition MRI [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-02-03.
• Pandey, A., Yoruk, U., Keerthivasan, M., Galons, J. P., Sharma, P., Johnson, K., Martin, D. R., Altbach, M. I., Bilgin, A., & Saranathan, M. (2017). Multiresolution imaging using golden angle stack-of-stars and compressed sensing for dynamic MR urography. Journal of magnetic resonance imaging : JMRI, 46(1), 303-311.
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  To develop a novel multiresolution MRI methodology for accurate estimation of glomerular filtration rate (GFR) in vivo.
• Rosado-Toro, J. A., Abidov, A., Altbach, M. I., Oliva, I. B., Rodriguez, J. J., & Avery, R. J. (2017). Segmentation of the right ventricle in four chamber cine cardiac MR images using polar dynamic programming. Computerized medical imaging and graphics : the official journal of the Computerized Medical Imaging Society, 62, 15-25.
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  The four chamber plane is currently underutilized in the right ventricular segmentation community. Four chamber information can be useful to determine ventricular short axis stacks and provide a rough estimate of the right ventricle in short axis stacks. In this study, we develop and test a semi-automated technique for segmenting the right ventricle in four chamber cine cardiac magnetic resonance images. The three techniques that use minimum cost path algorithms were used. The algorithms are: Dijkstra's shortest path algorithm (Dijkstra), an A* algorithm that uses length, curvature and torsion into an active contour model (ALCT), and a variation of polar dynamic programming (PDP). The techniques are evaluated against the expert traces using 175 cardiac images from 7 patients. The evaluation first looks at mutual overlap metrics and then focuses on clinical measures such as fractional area change (FAC). The mean mutual overlap between the physician's traces ranged from 0.85 to 0.88. Using as reference physician 1's landmarks and traces (i.e., comparing the traces from physician 1 to the semi-automated segmentation using physician 1's landmarks), the PDP algorithm has a mean mutual overlap of 0.8970 compared to 0.8912 for ALCT and 0.8879 for Dijkstra. The mean mutual overlap between the BP regions generated by physician 1 and physician 2 landmarks are 0.9674, 0.9605 and 0.9531 for PDP, ALCT and Dijkstra, respectively. The FAC correlation coefficient between the physician's traces ranged from 0.73 to 0.93.
• Stopeck, A., Stopeck, A., Marron, M. T., Wertheim, B. C., Wang, F., Thomson, C. A., Thompson, P. A., Roe, D. J., Marron, M. T., Huang, C., Galons, J., Ding, J., & Altbach, M. I. (2017). Abstract P6-09-19: Breast density change at 6 months is associated with change at 12 months as measured by fat-water decomposition MRI in women on tamoxifen. Cancer Research, 77(4_Supplement), P6-09-19-P6-09-19. doi:10.1158/1538-7445.sabcs16-p6-09-19
• Thomson, C. A., Chow, H. H., Wertheim, B. C., Roe, D. J., Stopeck, A., Maskarinec, G., Altbach, M., Chalasani, P., Huang, C., Strom, M. B., Galons, J. P., & Thompson, P. A. (2017). A randomized, placebo-controlled trial of diindolylmethane for breast cancer biomarker modulation in patients taking tamoxifen. Breast cancer research and treatment, 165(1), 97-107.
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  Diindolylmethane (DIM), a bioactive metabolite of indole-3-carbinol found in cruciferous vegetables, has proposed cancer chemoprevention activity in the breast. There is limited evidence of clinically relevant activity of DIM or long-term safety data of its regular use. A randomized, double-blind, placebo-controlled trial was conducted to determine the activity and safety of combined use of BioResponse DIM® (BR-DIM) with tamoxifen.
• Brand, J. F., Furenlid, L. R., Altbach, M. I., Galons, J., Bhattacharyya, A., Sharma, P., Bhattacharyya, T., Bilgin, A., & Martin, D. R. (2016). Task-based optimization of flip angle for fibrosis detection in T1-weighted MRI of liver. Journal of medical imaging (Bellingham, Wash.), 3(3), 035502.
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  Chronic liver disease is a worldwide health problem, and hepatic fibrosis (HF) is one of the hallmarks of the disease. The current reference standard for diagnosing HF is biopsy followed by pathologist examination; however, this is limited by sampling error and carries a risk of complications. Pathology diagnosis of HF is based on textural change in the liver as a lobular collagen network that develops within portal triads. The scale of collagen lobules is characteristically in the order of 1 to 5 mm, which approximates the resolution limit of in vivo gadolinium-enhanced magnetic resonance imaging in the delayed phase. We use MRI of formalin-fixed human ex vivo liver samples as phantoms that mimic the textural contrast of in vivo Gd-MRI. We have developed a local texture analysis that is applied to phantom images, and the results are used to train model observers to detect HF. The performance of the observer is assessed with the area-under-the-receiver-operator-characteristic curve (AUROC) as the figure-of-merit. To optimize the MRI pulse sequence, phantoms were scanned with multiple times at a range of flip angles. The flip angle that was associated with the highest AUROC was chosen as optimal for the task of detecting HF.
• Martinez, J. A., Chalasani, P., Thomson, C. A., Roe, D., Altbach, M., Galons, J., Stopeck, A., Thompson, P. A., Villa-Guillen, D. E., & Chow, H. S. (2016). Phase II study of metformin for reduction of obesity-associated breast cancer risk: a randomized controlled trial protocol. BMC cancer, 16, 500.
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  Two-thirds of U.S. adult women are overweight or obese. High body mass index (BMI) and adult weight gain are risk factors for a number of chronic diseases, including postmenopausal breast cancer. The higher postmenopausal breast cancer risk in women with elevated BMI is likely to be attributable to related metabolic disturbances including altered circulating sex steroid hormones and adipokines, elevated pro-inflammatory cytokines, and insulin resistance. Metformin is a widely used antidiabetic drug that has demonstrated favorable effects on metabolic disturbances and as such may lead to lower breast cancer risk in obese women. Further, the anti-proliferative effects of metformin suggest it may decrease breast density, an accepted biomarker of breast cancer risk.
• Rosado-Toro, J. A., Altbach, M. I., & Rodriguez, J. J. (2016). Dynamic Programming Using Polar Variance for Image Segmentation. IEEE Trans. on Image Processing, 25(12), 5857-5866. doi:10.1109/TIP.2016.2615809
• Rosado-Toro, J. A., Altbach, M. I., & Rodriguez, J. J. (2016). Dynamic Programming Using Polar Variance for Image Segmentation. IEEE transactions on image processing : a publication of the IEEE Signal Processing Society.
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  When using polar dynamic programming (PDP) for image segmentation, the object size is one of the main features used. This is because if size is left unconstrained the final segmentation may include high-gradient regions that are not associated with the object. In this paper, we propose a new feature, polar variance, which allows the algorithm to segment objects of different sizes without the need for training data. The polar variance is the variance in a polar region between a user-selected origin and a pixel we want to analyze. We also incorporate a new technique that allows PDP to segment complex shapes by finding low-gradient regions and growing them. The experimental analysis consisted on comparing our technique with different active contour segmentation techniques on a series of tests. The tests consisted on robustness to additive Gaussian noise, segmentation accuracy with different grayscale images and finally robustness to algorithm-specific parameters. Experimental results show that our technique performs favorably when compared to other segmentation techniques.
• Sharma, P., Altbach, M., Galons, J., Kalb, B., & Martin, D. R. (2016). Measurement of liver fat fraction and iron with MRI and MR spectroscopy techniques. Diagnostic and interventional radiology (Ankara, Turkey), 20(1), 17-26.
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  Diffuse liver disease is a widespread global healthcare burden, and the abnormal accumulation of lipid and/or iron is common to important disease processes. Developing the improved methods for detecting and quantifying liver lipid and iron is an important clinical need. The inherent risk, invasiveness, and sampling error of liver biopsy have prompted the development of noninvasive imaging methods for lipid and iron assessment. Ultrasonography and computed tomography have the ability to detect diffuse liver disease, but with limited accuracy. The purpose of this review is to describe the current state-of-the-art methods for quantifying liver lipid and iron using magnetic resonance imaging and spectroscopy, including their implementation, benefits, and potential pitfalls. Imaging- and spectroscopy-based methods are naturally suited for lipid and iron quantification. Lipid can be detected and decomposed from the inherent chemical shift between lipid and water signals, whereas iron imparts significant paramagnetic susceptibility to tissue, which accelerates proton relaxation. However, measurements of these biomarkers are confounded by technical and biological effects. Current methods must address these factors to allow a precise correlation between the lipid fraction and iron concentration. Although this correlation becomes increasingly challenging in the presence of combined lipid and iron accumulation, advanced techniques show promise for delineating these quantities through multi-lipid peak analysis, T2 water mapping, and fast single-voxel water-lipid spectroscopy.
• Trouard, T. P., Sabharwal, Y., Altbach, M. I., & Gmitro, A. F. (2016). Analysis and comparison of motion-correction techniques in diffusion-weighted imaging. Journal of magnetic resonance imaging : JMRI, 6(6), 925-35.
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  Motion continues to be a significant problem in MRI, producing image artifacts that can severely degrade image quality. In diffusion-weighted imaging (DWI), the problem is amplified by the presence of large gradient fields used to produce the diffusion weighting. Three correction methods applicable for correction of specific classes of motion are described and compared. The first is based on a generalised projection onto convex sets (GPOCS) postprocessing algorithm. The second technique uses the collection of navigator echoes to track phase errors. The third technique is based on a radial-scan data acquisition combined with a modified projection-reconstruction algorithm. Although each technique corrects well for translations, the radial-scan method proves to be more robust when more complex motions are present. A detailed description of the causes of MR data errors caused by rigid body motion is included as an appendix.
• Berman, B. P., Pandey, A., Li, Z., Jeffries, L., Trouard, T. P., Oliva, I., Cortopassi, F., Martin, D. R., Altbach, M. I., & Bilgin, A. (2015). Volumetric MRI of the lungs during forced expiration. Magnetic resonance in medicine.
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  Lung function is typically characterized by spirometer measurements, which do not offer spatially specific information. Imaging during exhalation provides spatial information but is challenging due to large movement over a short time. The purpose of this work is to provide a solution to lung imaging during forced expiration using accelerated magnetic resonance imaging. The method uses radial golden angle stack-of-stars gradient echo acquisition and compressed sensing reconstruction.
• Hagio, T., Huang, C., Abidov, A., Singh, J., Ainapurapu, B., Squire, S., Bruck, D., & Altbach, M. I. (2015). T2 mapping of the heart with a double-inversion radial fast spin-echo method with indirect echo compensation. Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance, 17, 24.
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  The abnormal signal intensity in cardiac T2-weighted images is associated with various pathologies including myocardial edema. However, the assessment of pathologies based on signal intensity is affected by the acquisition parameters and the sensitivities of the receiver coils. T2 mapping has been proposed to overcome limitations of T2-weighted imaging, but most methods are limited in spatial and/or temporal resolution. Here we present and evaluate a double inversion recovery radial fast spin-echo (DIR-RADFSE) technique that yields data with high spatiotemporal resolution for cardiac T2 mapping.
• Huang, C., Galons, J., Graff, C. G., Clarkson, E. W., Bilgin, A., Kalb, B., Martin, D. R., & Altbach, M. I. (2015). Correcting partial volume effects in biexponential T2 estimation of small lesions. Magnetic resonance in medicine, 73(4), 1632-42.
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  T2 mapping provides a quantitative approach for focal liver lesion characterization. For small lesions, a biexponential model should be used to account for partial volume effects (PVE). However, conventional biexponential fitting suffers from large uncertainty of the fitted parameters when noise is present. The purpose of this work is to develop a more robust method to correct for PVE affecting small lesions.
• Marron, M. T., Kupinski, M. A., Stopeck, A., Wertheim, B. C., Thomson, C. A., Thompson, P. A., Stopeck, A., Roe, D. J., Maskarinec, G., Marron, M. T., Kupinski, M. A., Galons, J., & Altbach, M. I. (2015). Abstract P6-01-18: 2-Hydroxyestrone is associated with breast density measured by mammography and fat:water ratio magnetic resonance imaging in women taking tamoxifen. Cancer Research, 75(9_Supplement), P6-01-18-P6-01-18. doi:10.1158/1538-7445.sabcs14-p6-01-18
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  Research Objectives and Rationale. Tamoxifen (TAM) use has been shown to reduce breast cancer recurrence with the benefit greater in patients who experience a TAM-associated decrease in percent mammographic density(PMD); findings that support PMD as a biomarker of response to TAM. PMD is a radiographic phenomenon of breast fibroglandular tissue that is associated with breast cancer risk. PMD is inversely associated with body mass index (BMI) and sparse data have shown a weak positive association with the sex hormone levels. Limited data exist evaluating the relationship between TAM, 2OHE1:16 a-OHE1 ratio (concentrations previously hypothesized to be associated with a reduced risk of breast cancer) and PBD. Methods. Using cross-sectional baseline breast density (BD) from an ongoing prevention trial of diindolylmethane (DIM) in 121 women receiving TAM, we evaluated BD in relation to circulating TAM metabolites [TAM, endoxifen, 4-OH TAM, ND TAM], estradiol (E2), sex hormone-binding globulin (SHBG) and urinary 2-OHE1 and 16α-OHE1. PMD was assessed by mammography (n=65; 54%) and also a novel, non-radiative, non-contrast magnetic resonance imaging-derived fat-water ratio (FWR-MRI) as the fat fraction (Fra)50 and 80 (n=53; 44%) developed for repeat BD assessment in short intervals. This is our first report that BD using digitized mammograms is correlated with FWR-MRI-derived measures designated Fra50 and Fra80; Spearman ρ = 0.90 and 0.86, respectively, p Results. As previously demonstrated, BMI was inversely correlated with all measures of BD. No association was shown between TAM and TAM metabolites and BD or urinary 2OHE1. Further, we found no relationship between circulating E2 or SHBG concentrations and BD. In contrast, urinary 2OHE1 levels were positively correlated with BD across all measures of density; 2OHE1 levels were most strongly correlated with BD measured by FW-MRI using Fra80 (Spearman ρFra80=0.483; p=0.001 compared to ρFra50 =0.431; p = 0.004 and ρPD=0.400; p=0.003). A significant, but weaker, correlation was observed for the 2OHE1:16OHE1 ratio and BD (ρ values 0.34-0.38). The magnitude of the relationship between 2OHE1 and BD was similar in pre and post-menopausal women despite lower PBD after menopause. Conclusions. Our results replicate earlier work from Maskarinec et al. wherein excreted 2OHE1 was an independent determinant of BD. These data challenge the hypothesis proposed by Yager and Liehr that higher urinary 2OHE1 to 16OHE1 ratio would be indicative of reduced hormone tumorigenesis. These results suggest a possible comparable binding affinity for the estrogen receptor that may modify endogenous steroid hormones and their effects on BD. Our findings strengthen the arguments favoring a better mechanistic understanding of BD, the biological determinants and their relationship to breast cancer. This is particularly timely given new mandates to provide BD measures to all women undergoing mammography and recent findings that while BD is associated with breast cancer risk high BD is not associated with greater breast cancer mortality. Citation Format: Cynthia A Thomson, Patricia A Thompson, Betsy C Wertheim, Denise Roe, Marilyn T Marron, John-Phillipe Galons, Matthew A Kupinski, Maria I Altbach, Gertraud Maskarinec, Alison Stopeck. 2-Hydroxyestrone is associated with breast density measured by mammography and fat:water ratio magnetic resonance imaging in women taking tamoxifen [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-01-18.
• Rosado-Toro, J. A., Barr, T., Galons, J., Marron, M. T., Stopeck, A., Thomson, C., Thompson, P., Caroll, D., Wolf, E., Altbach, M. I., & Rodriguez, J. J. (2015). Automated Breast Segmentation of Fat and Water MR Images Using Dynamic Programming. Academic Radiology, 22(2), 139-148. doi:10.1016/j.acra.2014.09.015
• Rosado-Toro, J. A., Barr, T., Galons, J., Marron, M. T., Stopeck, A., Thomson, C., Thompson, P., Carroll, D., Wolf, E., Altbach, M. I., & Rodríguez, J. J. (2015). Automated breast segmentation of fat and water MR images using dynamic programming. Academic radiology, 22(2), 139-48.
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  To develop and test an algorithm that outlines the breast boundaries using information from fat and water magnetic resonance images.
• Altbach, M. I., Martin, D. R., Kalb, B., Bilgin, A., Clarkson, E. W., Galons, J., Huang, C., & Graff, C. G. (2014). Correcting partial volume effects in biexponential T ₂ estimation of small lesions. Magnetic Resonance in Medicine, 73(4), 1632-1642. doi:10.1002/mrm.25250
• Huang, C., Altbach, M. I., & El Fakhri, G. (2014). Pattern recognition for rapid T2 mapping with stimulated echo compensation. Magnetic resonance imaging, 32(7), 969-74.
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  Indirect echoes (such as stimulated echoes) are a source of signal contamination in multi-echo spin-echo T2 quantification and can lead to T2 overestimation if a conventional exponential T2 decay model is assumed. Recently, nonlinear least square fitting of a slice-resolved extended phase graph (SEPG) signal model has been shown to provide accurate T2 estimates with indirect echo compensation. However, the iterative nonlinear least square fitting is computationally expensive and the T2 map generation time is long. In this work, we present a pattern recognition T2 mapping technique based on the SEPG model that can be performed with a single pre-computed dictionary for any arbitrary echo spacing. Almost identical T2 and B1 maps were obtained from in vivo data using the proposed technique compared to conventional iterative nonlinear least square fitting, while the computation time was reduced by more than 14-fold.
• Huang, C., Bilgin, A., & Altbach, M. I. (2013). Extending the capabilities of quantitative MRI. Spie Newsroom. doi:10.1117/2.1201309.005136
• Huang, C., Bilgin, A., Barr, T., & Altbach, M. I. (2013). T2 relaxometry with indirect echo compensation from highly undersampled data.. Magnetic resonance in medicine, 70(4), 1026-37. doi:10.1002/mrm.24540
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  To develop an algorithm for fast and accurate T2 estimation from highly undersampled multi-echo spin-echo data..The algorithm combines a model-based reconstruction with a signal decay based on the slice-resolved extended phase graph (SEPG) model with the goal of reconstructing T2 maps from highly undersampled radial multi-echo spin-echo data with indirect echo compensation. To avoid problems associated with the nonlinearity of the SEPG model, principal component decomposition is used to linearize the signal model. The proposed CUrve Reconstruction via principal component-based Linearization with Indirect Echo compensation (CURLIE) algorithm is used to estimate T2 curves from highly undersampled data. T2 maps are obtained by fitting the curves to the SEPG model..Results on phantoms showed T2 biases (1.9% to 18.4%) when indirect echoes are not taken into account. The T2 biases were reduced (< 3.2%) when the CURLIE reconstruction was performed along with SEPG fitting even for high degrees of undersampling (4% sampled). Experiments in vivo for brain, liver, and heart followed the same trend as the phantoms..The CURLIE reconstruction combined with SEPG fitting enables accurate T2 estimation from highly undersampled multi-echo spin-echo radial data thus, yielding a fast T2 mapping method without errors caused by indirect echoes.
• Ainapurapu, B., Galons, J. P., Squire, S., Singh, J., Kc, D. B., Huang, C., Galons, J. P., Barr, T., Altbach, M. I., Ainapurapu, B., & Abidov, A. (2012). T2 mapping of the heart with high temporal and spatial resolution using a radial double inversion fast spin-echo pulse sequence with view sharing. Journal of Cardiovascular Magnetic Resonance, 14(1), 1-2. doi:10.1186/1532-429x-14-s1-o112
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  Summary A double inversion radial fast spin echo (DIR-RADFSE) has been developed to obtain T2 maps of the heart with high-temporal and spatial resolution from data acquired in as ingle breath hold. The method allows for the quantitative assessment of inflammation in the heart. Background While DE imaging is considered a gold standard in the evaluation of myocardial scar/viability in patients with old MI or cardiomyopathy, a few recent publications demonstrate a higher diagnostic sensitivity of T2weighted techniques in patients with Non-STEMI and myocarditis where changes in T2-weighting are due to inflammation in the myocardium leading to edema (Abdel-Aty H, JACC 53:1194, 2009; Tilak GS, Invest
• Altbach, M., Huang, C., Bilgin, A., Barr, T., & Altbach, M. I. (2012). T(2) relaxometry with indirect echo compensation from highly undersampled data. Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine.
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  PURPOSE: To develop an algorithm for fast and accurate T(2) estimation from highly undersampled multi-echo spin-echo data. METHODS: The algorithm combines a model-based reconstruction with a signal decay based on the slice-resolved extended phase graph (SEPG) model with the goal of reconstructing T(2) maps from highly undersampled radial multi-echo spin-echo data with indirect echo compensation. To avoid problems associated with the nonlinearity of the SEPG model, principal component decomposition is used to linearize the signal model. The proposed CUrve Reconstruction via principal component-based Linearization with Indirect Echo compensation (CURLIE) algorithm is used to estimate T(2) curves from highly undersampled data. T(2) maps are obtained by fitting the curves to the SEPG model. RESULTS: Results on phantoms showed T(2) biases (1.9% to 18.4%) when indirect echoes are not taken into account. The T(2) biases were reduced (< 3.2%) when the CURLIE reconstruction was performed along with SEPG fitting even for high degrees of undersampling (4% sampled). Experiments in vivo for brain, liver, and heart followed the same trend as the phantoms. CONCLUSION: The CURLIE reconstruction combined with SEPG fitting enables accurate T(2) estimation from highly undersampled multi-echo spin-echo radial data thus, yielding a fast T(2) mapping method without errors caused by indirect echoes. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.
• Altbach, M., Huang, C., Graff, C. G., Clarkson, E. W., Bilgin, A., & Altbach, M. I. (2012). T2 mapping from highly undersampled data by reconstruction of principal component coefficient maps using compressed sensing. Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine, 67(5).
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  Recently, there has been an increased interest in quantitative MR parameters to improve diagnosis and treatment. Parameter mapping requires multiple images acquired with different timings usually resulting in long acquisition times. While acquisition time can be reduced by acquiring undersampled data, obtaining accurate estimates of parameters from undersampled data is a challenging problem, in particular for structures with high spatial frequency content. In this work, principal component analysis is combined with a model-based algorithm to reconstruct maps of selected principal component coefficients from highly undersampled radial MRI data. This novel approach linearizes the cost function of the optimization problem yielding a more accurate and reliable estimation of MR parameter maps. The proposed algorithm--reconstruction of principal component coefficient maps using compressed sensing--is demonstrated in phantoms and in vivo and compared with two other algorithms previously developed for undersampled data.
• Rajaraman, S., Rodriguez, J. J., Graff, C., Altbach, M. I., Dragovich, T., Sirlin, C. B., Korn, R. L., & Raghunand, N. (2011). Automated registration of sequential breath-hold dynamic contrast-enhanced MR images: a comparison of three techniques. Magnetic resonance imaging, 29(5), 668-82.
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  Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is increasingly in use as an investigational biomarker of response in cancer clinical studies. Proper registration of images acquired at different time points is essential for deriving diagnostic information from quantitative pharmacokinetic analysis of these data. Motion artifacts in the presence of time-varying intensity due to contrast enhancement make this registration problem challenging. DCE-MRI of chest and abdominal lesions is typically performed during sequential breath-holds, which introduces misregistration due to inconsistent diaphragm positions and also places constraints on temporal resolution vis-à-vis free-breathing. In this work, we have employed a computer-generated DCE-MRI phantom to compare the performance of two published methods, Progressive Principal Component Registration and Pharmacokinetic Model-Driven Registration, with Sequential Elastic Registration (SER) to register adjacent time-sample images using a published general-purpose elastic registration algorithm. In all three methods, a 3D rigid-body registration scheme with a mutual information similarity measure was used as a preprocessing step. The DCE-MRI phantom images were mathematically deformed to simulate misregistration, which was corrected using the three schemes. All three schemes were comparably successful in registering large regions of interest (ROIs) such as muscle, liver, and spleen. SER was superior in retaining tumor volume and shape, and in registering smaller but important ROIs such as tumor core and tumor rim. The performance of SER on clinical DCE-MRI data sets is also presented.
• Sorrell, V. L., Paleru, V., Altbach, M. I., Hilwig, R. W., Kern, K. B., Gaballa, M., Ewy, G. A., & Berg, R. A. (2011). Mild hypothermia delays the development of stone heart from untreated sustained ventricular fibrillation--a cardiovascular magnetic resonance study. Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance, 13, 17.
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  'Stone heart' resulting from ischemic contracture of the myocardium, precludes successful resuscitation from ventricular fibrillation (VF). We hypothesized that mild hypothermia might slow the progression to stone heart.
• Altbach, M., Li, Z., Graff, C., Gmitro, A. F., Squire, S. W., Bilgin, A., Outwater, E. K., & Altbach, M. I. (2009). Rapid water and lipid imaging with T2 mapping using a radial IDEAL-GRASE technique. Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine, 61(6).
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  Three-point Dixon methods have been investigated as a means to generate water and fat images without the effects of field inhomogeneities. Recently, an iterative algorithm (IDEAL, iterative decomposition of water and fat with echo asymmetry and least squares estimation) was combined with a gradient and spin-echo acquisition strategy (IDEAL-GRASE) to provide a time-efficient method for lipid-water imaging with correction for the effects of field inhomogeneities. The method presented in this work combines IDEAL-GRASE with radial data acquisition. Radial data sampling offers robustness to motion over Cartesian trajectories as well as the possibility of generating high-resolution T(2) maps in addition to the water and fat images. The radial IDEAL-GRASE technique is demonstrated in phantoms and in vivo for various applications including abdominal, pelvic, and cardiac imaging.
• Sorrell, V. L., Bilgin, A., Ata, I., & Altbach, M. I. (2008). 1084 A double-inversion radial FSE and GRASE methods for the evaluation of cardiac masses. Journal of Cardiovascular Magnetic Resonance, 10(1), 1-3. doi:10.1186/1532-429x-10-s1-a209
• Trouard, T. P., Lalgudi, H. G., Kim, Y., Bilgin, A., & Altbach, M. I. (2008). Parallel magnetic resonance imaging using compressed sensing. Proceedings of SPIE, 7073. doi:10.1117/12.797206
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  Although magnetic resonance imaging (MRI) is routinely used in clinical practice, long acquisition times limit its practical utility in many applications. To increase the data acquisition speed of MRI, parallel MRI (pMRI) techniques have recently been proposed. These techniques utilize multi-channel receiver arrays and are based on simultaneous acquisition of data from multiple receiver coils. Recently, a novel framework called Compressed Sensing (CS) was introduced. Since this new framework illustrates how signals can be reconstructed from much fewer samples than suggested by the Nyquist theory, it has the potential to significantly accelerate data acquisition in MRI. This paper illustrates that CS and pMRI techniques can be combined and such joint processing yields results that are superior to those obtained from independent utilization of each technique.
• Altbach, M. I., Squire, S. W., Kudithipudi, V., Castellano, L., & Sorrell, V. L. (2007). Cardiac MRI is complementary to echocardiography in the assessment of cardiac masses. Echocardiography (Mount Kisco, N.Y.), 24(3), 286-300.
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  Despite the fact that the incidence of cardiac tumors is low, the prompt evaluation and adequate intervention of these is highly important. Although most tumors of the heart are considered histologically benign, there are significant risks associated with these "benign" tumors. These are associated with significant morbidity and mortality due to obstruction of blood flow, alterations of conduction, propagation of arrhythmias, and thromboembolism, depending on their size, location, and nature. With the advent of noninvasive imaging modalities--traditionally echocardiography; but more recently using cross-sectional imaging with cardiac computed tomography and magnetic resonance imaging--cardiac tumors can be optimally assessed providing a greater opportunity for curative treatments by cardiothoracic surgery.
• Altbach, M., Li, Z., Gmitro, A. F., Bilgin, A., & Altbach, M. I. (2007). Fast decomposition of water and lipid using a GRASE technique with the IDEAL algorithm. Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine, 57(6).
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  Three-point Dixon techniques achieve good lipid-water separation by estimating the phase due to field inhomogeneities. Recently it was demonstrated that the combination of an iterative algorithm (iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL)) with a fast spin-echo (FSE) three-point Dixon method yielded robust lipid-water decomposition. As an alternative to FSE, the gradient- and spin-echo (GRASE) technique has been developed for efficient data collection. In this work we present a method for lipid-water separation by combining IDEAL with the GRASE technique. An approach to correct for errors in the lipid-water decomposition caused by phase distortions due to the switching of the readout gradient polarities inherent to GRASE is presented. The IDEAL-GRASE technique is demonstrated in phantoms and in vivo for various applications, including pelvic, musculoskeletal, and (breath-hold) cardiac imaging.
• Squire, S., Sorrell, V. L., Kudithipudi, V., Kern, K. B., Hilwig, R. W., Ewy, G. A., Bhatt, R. D., Berg, R. A., & Altbach, M. I. (2007). Cardiac magnetic resonance imaging investigation of sustained ventricular fibrillation in a swine model--with a focus on the electrical phase.. Resuscitation, 73(2), 279-86. doi:10.1016/j.resuscitation.2006.08.032
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  We sought to develop a method to evaluate the rapidly changing cardiac dimensions during sustained ventricular fibrillation (VF). We also present details of our CPR research imaging program to facilitate this avenue of clinically important research..The changes in cardiac dimensions occurring during the initial critical electrical phase of sustained VF are not entirely known. Conventional cardiac magnetic resonance imaging (CMR) functional imaging lacks the temporal resolution necessary to capture the dynamic changes within this early time period of sustained VF. We hypothesized that changes in the middle short axis slice of the ventricles will reflect changes in ventricular volumes accurately..Ventricular dimensions were determined from CMR for 30 min of untreated VF in a closed chest, closed pericardium model in seven swine. Ungated steady-state free precession images (SSFP) from the cardiac base to the apex were acquired, taking care to align the anatomical short axis (SAX) imaging planes maximally. The middle slice of the ventricles was determined as the mathematical center of the stack of SAX slices. We then compared the relative changes of right ventricle (RV) and left ventricle (LV) volumes to relative changes in mid-ventricular single slice area..During 30 min of sustained VF, there was an excellent correlation between the changes in exact mid-slice area and the quantitative changes in ventricular volumes (r(2)>0.95)..Mid-slice area data can be used as a surrogate marker of prompt ventricular volume changes during VF. By imaging the heart 10 times faster, the rapid anatomical changes occurring during the initial few minutes of sustained VF can be understood better.
• Altbach, M. I., Bilgin, A., Li, Z., Clarkson, E. W., Trouard, T. P., & Gmitro, A. F. (2005). Processing of radial fast spin-echo data for obtaining T2 estimates from a single k-space data set. Magnetic resonance in medicine, 54(3), 549-59.
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  Radially acquired fast spin-echo data can be processed to obtain T2-weighted images and a T2 map from a single k-space data set. The general approach is to use data at a specific TE (or narrow TE range) in the center of k-space and data at other TE values in the outer part of k-space. With this method high-resolution T2-weighted images and T2 maps are obtained in a time efficient manner. The mixing of TE data, however, introduces errors in the T2-weighted images and T2 maps that affect the accuracy of the T2 estimates. In this work, various k-space data processing methods for reconstructing T2-weighted images and T2 maps from a single radial fast spin-echo k-space data set are analyzed in terms of the accuracy of T2 estimates. The analysis is focused on the effect of image artifacts, object dependency, and noise on the T2 estimates. Results are presented in computer-generated phantoms and in vivo.
• Altbach, M. I., Li, Z., Bilgin, A., Marcus, F. I., Sorrell, V. L., Gmitro, A. F., & Bluemke, D. A. (2005). Interleaved acquisition of lipid and water images of the heart using a double-inversion fast spin-echo method. Magnetic resonance in medicine, 54(6), 1562-8.
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  In this work we present a new method for the improved detection of lipid infiltration in the heart. The method employs a double-inversion fast spin-echo technique where the acquisition of water- and lipid-suppressed k-space data is alternated between TR periods to produce co-registered lipid and water images from data acquired in a breath hold. The lipid and water images can then be combined to generate a lipid/water image with reduced artifacts due to flow and excellent contrast between lipid and myocardium. The method is demonstrated in ex vivo tissue and in vivo. This novel method may improve the detection of lipid infiltration in the heart in pathologies such as arrhythmogenic right ventricular dysplasia.
• Berg, R. A., Sorrell, V. L., Kern, K. B., Hilwig, R. W., Altbach, M. I., Hayes, M. M., Bates, K. A., & Ewy, G. A. (2005). Magnetic resonance imaging during untreated ventricular fibrillation reveals prompt right ventricular overdistention without left ventricular volume loss. Circulation, 111(9), 1136-40.
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  Most out-of-hospital ventricular fibrillation (VF) is prolonged (>5 minutes), and defibrillation from prolonged VF typically results in asystole or pulseless electrical activity. Recent visual epicardial observations in an open-chest, open-pericardium model of swine VF indicate that blood flows from the high-pressure arterial system to the lower-pressure venous system during untreated VF, thereby overdistending the right ventricle and apparently decreasing left ventricular size. Therefore, inadequate left ventricular stroke volume after defibrillation from prolonged VF has been postulated as a major contributor to the development of pulseless rhythms.
• Gmitro, A. F., Kono, M., Theilmann, R. J., Altbach, M. I., Li, Z., & Trouard, T. P. (2005). Radial GRASE: implementation and applications. Magnetic resonance in medicine, 53(6), 1363-71.
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  RAD-GRASE is an MRI sequence that combines radial (RAD) k-space scanning with the gradient and spin-echo (GRASE) technique. RAD-GRASE has the advantages of all radial data acquisition methods in that it can reduce motion sensitivity and correct motion-induced data errors, which can be exploited to achieve high-resolution diffusion-weighted imaging (DWI). One can obtain different types of image contrast, including DWI, T(1), T(2), and T(2)*, in RAD-GRASE by controlling the magnetization preparation and sequence timing. Moreover, because there is oversampling of the low spatial frequencies inherent to radial sequences, partial data reconstruction can be used to achieve multiple forms of image contrast from a single acquired data set, and to generate parametric image maps of equilibrium magnetization, T(2), and T(2) (dagger). The RAD-GRASE technique can also be used to achieve fat-suppressed and/or separated fat and water images by choosing the appropriate timing parameters.
• Sarlls, J. E., Newbould, R. D., Altbach, M. I., Gmitro, A. F., Seeger, J., & Trouard, T. P. (2005). Isotropic diffusion weighting in radial fast spin-echo magnetic resonance imaging. Magnetic resonance in medicine, 53(6), 1347-54.
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  Radial fast spin-echo (radial-FSE) methods enable multishot diffusion-weighted MRI (DWMRI) to be carried out without significant artifacts due to motion and/or susceptibility and can be used to generate DWMRI images with high spatial resolution. In this work, a novel method that allows isotropic diffusion weighting to be obtained in a single radial k-space data set is presented. This is accomplished by altering the direction of diffusion weighting gradients between groups of TR periods, which yield sets of radial lines that possess diffusion weighting sensitive to motion in different directions. By altering the diffusion weighting directions and controlling the view ordering appropriately within the sequence, an effectively isotropic diffusion-weighted image can be obtained within one radial-FSE scan. The order in which radial lines are acquired can also be controlled to yield data sets without significant artifacts due to motion, T(2) decay, and/or diffusion anisotropy.
• Sorrell, V. L., Altbach, M. I., Kern, K. B., Squire, S., Hilwig, R. W., Hayes, M. M., Ewy, G. A., & Berg, R. A. (2005). Images in cardiovascular medicine. Continuous cardiac magnetic resonance imaging during untreated ventricular fibrillation. Circulation, 111(19), e294.
• Theilmann, R. J., Gmitro, A. F., Altbach, M. I., & Trouard, T. P. (2004). View-ordering in radial fast spin-echo imaging. Magnetic resonance in medicine, 51(4), 768-74.
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  Radial MRI sequences are frequently used to obtain images with reduced sensitivity to motion. To decrease imaging time, multiple spin-echo acquisitions can be incorporated into radial sequences. In this case, different radial lines of Fourier data have different TE times and the resulting images can contain streaking artifacts due to T(2) decay. The streaking is not only dependent on the T(2) of the object and the timing of the data acquisition, but also on the order in which radial lines are collected (view order). The view ordering can easily be controlled to minimize artifacts due to T(2) decay as well as motion. Four view-ordering techniques are presented and evaluated for the radial FSE sequence.
• Marcellin, M. W., Marcellin, M. W., Bilgin, A., & Altbach, M. I. (2003). Compression of electrocardiogram signals using JPEG2000. IEEE Transactions on Consumer Electronics, 49(4), 833-840. doi:10.1109/tce.2003.1261162
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  JPEG2000 is the latest international standard for compression of still images. Although the JPEG2000 codec is designed to compress images, we illustrate that it can also be used to compress other signals. As an example, we illustrate how the JPEG2000 codec can be used to compress electrocardiogram (ECG) data. Experiments using the MIT-BIH arrhythmia database illustrate that the proposed approach outperforms many existing ECG compression schemes. The proposed scheme allows the use of existing hardware and software JPEG2000 codecs for ECG compression, and can be especially useful in eliminating the need for specialized hardware development. The desirable characteristics of the JPEG2000 codec, such as precise rate control and progressive quality, are retained in the presented scheme. The goal of this paper is to demonstrate the ECG application as an example. This example can be extended to other signals that exist within the consumer electronics realm.
• Altbach, M. I., Outwater, E. K., Trouard, T. P., Krupinski, E. A., Theilmann, R. J., Stopeck, A. T., Kono, M., & Gmitro, A. F. (2002). Radial fast spin-echo method for T2-weighted imaging and T2 mapping of the liver. Journal of magnetic resonance imaging : JMRI, 16(2), 179-89.
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  To evaluate a multishot radial fast-spin echo (RAD-FSE) method developed to improve the quality of abdominal T2-weighted imaging as well as the characterization of focal liver lesions.
• Altbach, M. I., Trouard, T. P., Van de Walle, R., Theilmann, R. J., Clarkson, E., Barrett, H. H., & Gmitro, A. F. (2001). Chemical-shift imaging utilizing the positional shifts along the readout gradient direction. IEEE transactions on medical imaging, 20(11), 1156-66.
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  In this work, we describe a method that uses the linear phase acquired during the readout period due to chemical shift to generate individual magnetic resonance (MR) images of chemically shifted species. The method utilizes sets of Fourier (or k-space) data acquired with different directions of the readout gradient and a postprocessing algorithm to generate chemical shift images. The methodology is developed for both Cartesian data acquisition and for radial data acquisition. The method is presented here for two chemically shifted species but it can be extended to more species. In this work, we present the theory, show the results in phantoms and in human images, and discuss the artifacts and signal-to-noise ratio of the images obtained with the technique.
• Van de Walle, R., Barrett, H. H., Myers, K. J., Altbach, M. I., Desplanques, B., Gmitro, A. F., Cornelis, J., & Lemahieu, I. (2000). Reconstruction of MR images from data acquired on a general nonregular grid by pseudoinverse calculation. IEEE transactions on medical imaging, 19(12), 1160-7.
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  A minimum-norm least-squares image-reconstruction method for the reconstruction of magnetic resonance images from non-Cartesian sampled data is proposed. The method is based on a general formalism for continuous-to-discrete mapping and pseudoinverse calculation. It does not involve any regridding or interpolation of the data and therefore the methodology differs fundamentally from existing regridding-based methods. Moreover, the method uses a continuous representation of objects in the image domain instead of a discretized representation. Simulations and experiments show the possibilities of the method in both radial and spiral imaging. Simulations revealed that minimum-norm least-squares image reconstruction can result in a drastic decrease of artifacts compared with regridding-based reconstruction. Besides, both in vivo and phantom experiments showed that minimum-norm least-squares image reconstruction leads to contrast improvement and increased signal-to-noise ratio compared with image reconstruction based on regridding. As an appendix, an analytical calculation of the raw data corresponding to the well-known Shepp and Logan software head phantom is presented.
• Galons, J. P., Altbach, M. I., Paine-Murrieta, G. D., Taylor, C. W., & Gillies, R. J. (1999). Early increases in breast tumor xenograft water mobility in response to paclitaxel therapy detected by non-invasive diffusion magnetic resonance imaging. Neoplasia (New York, N.Y.), 1(2), 113-7.
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  An important goal in cancer chemotherapy is to sensitively and quantitatively monitor the response of individual patients' tumors to successful, or unsuccessful, therapy so that regimens can be altered iteratively. Currently, tumor response is monitored by frank changes in tumor morphology, yet these markers take long to manifest and are not quantitative. Recent studies suggest that the apparent diffusion coefficient of water (ADCw), measured noninvasively with magnetic resonance imaging, is sensitively and reliably increased in response to successful CTx. In the present study, we investigate the combination chemotherapy response of human breast cancer tumor xenografts sensitive or resistant to Paclitaxel by monitoring changes in the ADCw. Our results indicate that there is a clear, substantial, and early increase in the ADCw after successful therapy in drug sensitive tumors and that there is no change in the ADCw in p-glycoprotein-positive tumors, which are resistant to Paclitaxel. The mechanism underlying these changes is unknown yet is consistent with apoptotic cell shrinkage and a concomitant increase in the extracellular water fraction.
• Raghunand, N., Altbach, M. I., van Sluis, R., Baggett, B., Taylor, C. W., Bhujwalla, Z. M., & Gillies, R. J. (1999). Plasmalemmal pH-gradients in drug-sensitive and drug-resistant MCF-7 human breast carcinoma xenografts measured by 31P magnetic resonance spectroscopy. Biochemical pharmacology, 57(3), 309-12.
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  31p Magnetic resonance spectroscopy (MRS) was employed to investigate tumor pH in xenografts of drug-sensitive and drug-resistant MCF-7 human breast carcinoma cells. Measured extracellular pH values were found to be lower than the intracellular pH in all three tumor types investigated. The magnitude of this acid-outside plasmalemmal pH gradient increased with increasing tumor size in tumors of two drug-resistant variants of MCF-7 cells, but not in tumors of the parent (drug-sensitive) cells. The partitioning of weak-base or weak-acid drug molecules across the plasma membrane of a tumor cell is dependent upon the acid-dissociation constant (pKa) of the drug as well as the plasmalemmal pH gradient. A large acid-outside pH gradient, such as those seen in MCF-7 xenografts, can exert a protective effect on the cell from weak-base drugs such as anthracyclines and Vinca alkaloids, which have pKa values of 7.5 to 9.5. The possibility of enhancing the therapeutic efficacy of weak-base drugs by dietary or metabolic manipulation of the extracellular pH, in order to reduce or reverse the plasmalemmal pH gradient, deserves investigation.
• Trouard, T. P., Theilmann, R. J., Altbach, M. I., & Gmitro, A. F. (1999). High-resolution diffusion imaging with DIFRAD-FSE (diffusion-weighted radial acquisition of data with fast spin-echo) MRI. Magnetic resonance in medicine, 42(1), 11-8.
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  A novel MRI method, DIFRAD-FSE (diffusion-weighted radial acquisition of data with fast spin-echo), is demonstrated that enables rapid, high-resolution multi-shot diffusion-weighted MRI without significant artifacts due to motion. Following a diffusion-weighting spin-echo preparation period, multiple radial lines of Fourier data are acquired using spin-echo refocusing. Images can be reconstructed from the radial data set using a magnitude-only filtered back-projection reconstruction algorithm that removes phase errors due to motion. Results from human brain imaging demonstrate the ability of DIFRAD-FSE to acquire multiple radial lines of Fourier data each TR period without significant artifacts due to relaxation and to produce high-resolution diffusion-weighted MRI images without significant artifacts from motion.
• Butler, L. G., Altbach, M. I., & Aeja, W. (1997). Deuterium NMR Studies of $({\mu}_3-C^2H)[Co(CO)_3]_3$. Journal of the Korean magnetic resonance society, 1(2), 95-102.
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  Deuterium quadrupole coupling constant (e2qzzQ/h) of (3-C2H)[Co(CO)3]3 was determined by using solid-state deuterium MAS NMR spectroscopy. The small quadrupole coupling constant of bridging methyne unit relative to sp-acethylene in propyne is discussed in terms of the C-H bond length and the negative charge on the carbon.
• Trouard, T. P., Altbach, M. I., Hunter, G. C., Eskelson, C. D., & Gmitro, A. F. (1997). MRI and NMR spectroscopy of the lipids of atherosclerotic plaque in rabbits and humans. Magnetic resonance in medicine, 38(1), 19-26.
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  The early stages of atherosclerosis are characterized by the deposition of cholesteryl esters and triglycerides into the arterial wall. In the excised human atherosclerotic plaque these lipids are in a liquid-like state at body temperature and observable via MRI and NMR spectroscopy. To assess the ability of MRI to quantitatively image the lipids of atherosclerotic plaque in vivo, we have investigated eight New Zealand White rabbits fed atherogenic diets (2 weight (wt)% cholesterol, 1 wt% cholesterol + 6 wt% peanut oil, and 1 wt% cholesterol + 6 wt% com oil). Postmortem examination indicated that all rabbits developed atherosclerosis in the aorta. Except for one animal, magnetic resonance angiography showed no noticeable obstruction in the aorta. MRI was carried out in an attempt to image atherosclerotic plaque lipids directly, but no signal was detected in vivo. However, a plaque lipid signal was observed from excised tissue using a small diameter RF coil. 1H NMR spectroscopy of the atherosclerotic plaque from excised aortas indicated that the major fraction of plaque lipids in rabbits is not in a liquid state at physiological temperature and are only marginally MRI-visible compared to human plaque lipid. The differences in the MRI characteristics of rabbit and human plaque are due to differences in the fatty acid profile of the cholesteryl esters, chiefly a decrease of linoleic acid in rabbit lesions.
• Inisan, A. G., Meunier, S., Fedelli, O., Altbach, M., Fremont, V., Sabatier, J. M., Thévan, A., Bernassau, J. M., Cambillau, C., & Darbon, H. (1995). Structure-activity relationship study of a scorpion toxin with high affinity for apamin-sensitive potassium channels by means of the solution structure of analogues. International journal of peptide and protein research, 45(5), 441-50.
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  Scorpion venoms contain numerous toxic polypeptides displaying various pharmacological activities. These toxins interact with ion channels of excitable membranes. Long toxins (60-70 amino acids) are known to interact with sodium channels, whereas most of the short toxins (31-37 amino acids) found their toxicity in modifying the potassium channel functions. A family of short scorpion toxins are known to interact specifically with apamin-sensitive calcium-activated potassium channels. Structure-activity relationship studies of these toxins have demonstrated that a short region located on the solvent-exposed side of an alpha-helix is involved in the interaction with their receptor. Two positions, i.e. residues 6 and 7 in the sequence, are essential for the full activity of these molecules. We have synthesized analogues of these toxins and demonstrated that the three-dimensional structure is not affected by these mutations, and thus that the observed variations of activity are only due to the chemical function carried by the side chain. This interaction between the toxins and their receptor is thus purely electrostatic.
• Altbach, M. I., Mattingly, M. A., Brown, M. F., & Gmitro, A. F. (1991). Magnetic resonance imaging of lipid deposits in human atheroma via a stimulated-echo diffusion-weighted technique. Magnetic resonance in medicine, 20(2), 319-26.
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  NMR images of subintimal lipid deposits within the vessel walls of atherosclerotic human aortas were obtained at 37 and 27 degrees C at 4.7 T. A combination of a stimulated-echo and pulsed-field gradients was used for suppressing the mobile tissue water relative to the less mobile tissue lipids. At 27 degrees C there was also a substantial reduction of the subintimal lipid signal intensity, which is consistent with the characteristic phase transition of cholesteryl esters in human atheroma. These results represent the first direct detection of lipid deposits in nonprotruding atherosclerotic lesions with NMR imaging.
• Wittebort, R. J., Hiyama, Y., Butler, L. G., & Altbach, M. I. (1990). Rotation of the cyclopentadienyl ligand in bis(μ-carbonyl)bis(carbonylcyclopentadienyliron)(Fe-Fe) in the solid state as determined from solid-state deuterium NMR spectroscopy. Inorganic Chemistry, 29(4), 741-747. doi:10.1021/ic00329a034
• Hiyama, Y., Gerson, D. J., Butler, L. G., & Altbach, M. I. (1987). Determination of the charge on carbon in a bridging methylene iron dimer with solid-state deuterium NMR spectroscopy. Journal of the American Chemical Society, 109(18), 5529-5531. doi:10.1021/ja00252a041
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  The chemistry of bridging methylene metal dimers and the value of the /sup 13/C NMR chemical shifts have been interpreted as due to a partial negative charge on the carbon atom. PES yields a C/sub 1s/ binding energy indicative of -0.5 e charge. However, for (..mu..-CH/sub 2/)(MnCp(CO)/sub 2/)/sub 2/, a high-resolution x-ray diffraction electron density map shows no excess charge buildup. The authors are attempting to resolve the dilemma by using solid-state deuterium NMR techniques. In the results for cis-(..mu..-C/sup 2/H/sub 2/)(..sigma..-CO)(FeCp/sup d/(CO))/sub 2/ (Cp/sup d/ and 5% deuteriated cyclopentadienyl) presented here, the authors find no evidence for an excess negative charge on the bridging methylene carbon atom.

Proceedings Publications

• Altbach, M. I. (2023, June). Abstracts presented in 2023. In ISMRM 2023.
• Altbach, M. I. (2021). Presentation at the Annual ISMRM Meeting. In ISMRM.
• Bilgin, A., Altbach, M. I., Johnson, K., Fu, Z., & Ahanonu, E. (2021). Improved Slice Coverage in Inversion Recovery Radial Balanced-SSFP using Deep Learning. In Annual Meeting of the International Society for Magnetic Resonance in Medicine.
• Altbach, M. I. (2020, August). Titles for 2020 are listed in attached file. In International Society of Magnetic Resonance in Medicine.
• Altbach, M. I. (2018, Summer). Proceedings 2018 - A total of 15 publications listed in the attachment. In International Society for Magnetic Resonance in Medicine.
• Altbach, M. I., Bilgin, A., Martin, D. R., Weinkauf, C. C., Saranathan, M., Johnson, K., & Keerthivasan, M. B. (2018, June). An Optimized 3D Stack-of-Stars TSE Pulse Sequence for Simultaneous T2-weighted Imaging and T2 Mapping. In 2018 Meeting of the International Society for Magnetic Resonance in Medicine.
• Altbach, M. I., Johnson, K., Bilgin, A., Martin, D. R., Galons, J., Keerthivasan, M. B., Unger, W. D., Saranathan, M., & Pandey, A. (2018, June). Quantifying hepatic fibrosis using 3D radial golden angle stack-of stars acquisition and a dual input two compartment model. In 2018 Meeting of the International Society for Magnetic Resonance in Medicine.
• Altbach, M. I., Martin, D. R., Saranathan, M., Galons, J., Johnson, K., Bilgin, A., Li, Z., Altbach, M. I., Martin, D. R., Saranathan, M., Galons, J., Johnson, K., Bilgin, A., Li, Z., Li, Z., Bilgin, A., Johnson, K., Galons, J., Saranathan, M., , Martin, D. R., et al. (2018, June). Rapid multi-slice abdominal T1 mapping with IR-radSSFP. In 2018 Meeting of the International Society for Magnetic Resonance in Medicine.
• Bilgin, A., Altbach, M. I., Martin, D. R., Keerthivasan, M. B., & Mandava, S. (2018, June). Radial streaking artifact reduction using phased array beamforming. In 2018 Meeting of the International Society for Magnetic Resonance in Medicine.
• Bilgin, A., Altbach, M. I., Martin, D. R., Li, Z., & Mandava, S. (2018, June). A non-local low rank approach for high resolution parameter mapping. In 2018 Meeting of the International Society for Magnetic Resonance in Medicine.
• Bilgin, A., Altbach, M. I., Martin, D. R., Li, Z., Keerthivasan, M. B., Mandava, S., & Fu, Z. (2018, October). MR Parameter Mapping Using Sequential Multi-Contrast Acquisitions & Multi-Input Multi-Scale ResNet. In ISMRM Workshop on Machine Learning Part II.
• Bilgin, A., Altbach, M. I., Martin, D. R., Unger, W. D., Galons, J., Keerthivasan, M. B., & Umapathy, L. (2018, June). A Comparison of Deep Learning Convolutional Neural Networks for Liver Segmentation in Radial Turbo Spin Echo Images. In 2018 Meeting of the International Society for Magnetic Resonance in Medicine.
• Fu, Z., Mandava, S., Keerthivasan, M. B., Martin, D. R., Altbach, M. I., & Bilgin, A. (2018, June). A Multi-Scale Deep ResNet for MR Parameter Mapping. In 2018 Meeting of the International Society for Magnetic Resonance in Medicine.
• Keerthivasan, M. B., Blew, D., Galons, J., Martin, D. R., Bilgin, A., & Altbach, M. I. (2018, June). Characterization of Abdominal Neoplasms using a Fast T2 Mapping Radial TSE Technique. In 2018 Meeting of the International Society for Magnetic Resonance in Medicine.
• Li, Z., Bilgin, A., Johnson, K., Arif Tiwari, H., Martin, D. R., & Altbach, M. I. (2018, June). High-resolution 3D T1 mapping of the prostate with an efficient inversion-recovery radial FLASH. In 2018 Meeting of the International Society for Magnetic Resonance in Medicine.
• Lindley, M., Bernstein, A., Ugonna, C., Bruck, D., Johnson, K., Altbach, M. I., Ryan, L., Chen, N., Chou, Y., Guzman Perez-Carrillo, G., Trouard, T. P., & Weinkauf, C. C. (2018, June). Impact of Carotid Endarterectomy on Functional Connectivity. In Joint International Society for Magnetic Resonance in Medicine & The European Society for Magnetic Resonance in Medicine and Biology (ISMRM-ESMRMB) Annual Meeting, 5562.
• Mandava, S., Keerthivasan, M. B., Martin, D. R., Altbach, M. I., & Bilgin, A. (2018, June). Higher-order subspace denoising for improved multi-contrast imaging and parameter mapping. In 2018 Meeting of the International Society for Magnetic Resonance in Medicine.
• Saranathan, M., Altbach, M. I., Bilgin, A., Udayasankar, U., Winegar, B., & Keerthivasan, M. B. (2018, June). An Optimized Single-shot Sequence for Fast T2W Imaging of the Brain. In 2018 Meeting of the International Society for Magnetic Resonance in Medicine.
• Saranathan, M., Altbach, M. I., Bilgin, A., Udayasankar, U., Winegar, B., & Keerthivasan, M. B. (2018, June). An optimized single-shot sequence for fast T2w imaging of the brain. In ISMRM annual meeting.
• Weinkauf, C. C., Altbach, M. I., Altbach, M. I., Mandava, S., Mandava, S., Bilgin, A., Johnson, K., Johnson, K., Becker, J., Li, Z., Li, Z., Keerthivasan, M. B., Keerthivasan, M. B., Keerthivasan, M. B., Li, Z., Johnson, K., Becker, J., Becker, J., Mandava, S., , Bilgin, A., et al. (2018, June). Rapid Carotid Artery T2 and T1 Mapping Using a Radial TSE and IR-FLASH Approach. In 2018 Meeting of the International Society for Magnetic Resonance in Medicine.
• Altbach, M. I., Martin, D. R., Bilgin, A., Saranathan, M., & Keerthivasan, M. B. (2017, May). High-resolution 3D T2 mapping using a stack-of-stars radial FSE pulse sequence. In 25th Annual meeting of ISMRM, 3957.
• Keerthivasan, M. B., Altbach, M. I., Saranathan, M., Bilgin, A., Galons, J., Martin, D. R., Martin, D. R., Galons, J., Bilgin, A., Saranathan, M., Keerthivasan, M. B., & Altbach, M. I. (2017, May). Variable Flip Angle Radial Turbo Spin Echo Technique for Abdominal T2 Mapping. In 25th Annual meeting of ISMRM, 72.
• Saranathan, M., Altbach, M. I., Becker, J., Martin, D. R., Bilgin, A., & Keerthivasan, M. B. (2017, May). Clinical utility of a novel ultrafast T2 Weighted sequence for Spine Imaging.. In 25th Annual meeting of ISMRM, 538.
• Saranathan, M., Bilgin, A., Altbach, M. I., Martin, D. R., Johnson, K., Galons, J., & Pandey, A. (2017, May). Glomerular filtration rate estimation in vivo using 3D radial MRI and a novel multiresolution reconstruction technique.. In 25th Annual meeting of ISMRM, 823.
• Altbach, M. I. (2016, May/November). See attached file for proceedings published or submitted in 2016. In ISMRM.
• Berman, B., Keerthivasan, M., Li, Z., Martin, D., Altbach, M. I., & Bilgin, A. (2015, May). Dictionary Learning for Compressive T2 Mapping with Non-Cartesian Trajectories and Parallel Imaging. In ISMRM.
• Brand, J., Furenlid, L., & Altbach, M. I. (2015, May). Autocorrelation Analysis of Hepatic Fibrosis on MRI. In ISMRM.
• Keerthivasan, M., Bilgin, A., Martin, D., & Altbach, M. I. (2015, May). Isotropic T2 Mapping using a 3D Radial FSE (or TSE) pulse sequence. In ISMRS.
• Li, Z., Berman, B., Martin, D., Altbach, M. I., & Bilgin, A. (2015, May). Efficient Dictionary Design for MR Fingerprinting using Tree-Structured Vector Quantization. In ISMRM.
• Mandava, S., Keerthivasan, M., Bilgin, A., Martin, D., & Altbach, M. I. (2015, May). Improved slice coverage in DBIR-FSE with multi-band encoding. In ISMRM.
• Rosado-Toro, J., Hagio, T., Marron, M., Galons, J., Thompson, P., Stopeck, A., Rodriguez, J., & Altbach, M. I. (2015, May). Automatic Segmentation of Breast Images Using Clustering and Dynamic Programming. In ISMRM.
• Rosado-Toro, J. A., Barr, T., Galons, J., Marron, M. T., Stopeck, A., Thomson, C., Altbach, M. I., Rodriguez, J. J., Rosado-Toro, J. A., Barr, T., Galons, J., Marron, M. T., Stopeck, A., Thomson, C., Altbach, M. I., & Rodriguez, J. J. (2013, May 26-31). Automated Segmentation of Breast Fat-Water MR Images Using Empirical Analysis. In 2013 IEEE Intl. Conf. on Acoustics, Speech, and Signal Processing, 1018-1022.
• Ryan, L., Trouard, T. P., Ryan, L., Pu, L., Huang, C., Bilgin, A., & Altbach, M. I. (2011). Model-based compressive diffusion tensor imaging. In 2011 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, 254-257.
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  Diffusion tensor imaging (DTI) is a Magnetic Resonance Imaging (MRI) technique that can reveal in vivo tissue microstructure by measuring diffusion of water in tissue. DTI has become an important tool in many clinical applications, such as assessment of white matter maturation, locating white matter lesions, and providing anatomical connectivity information. However, DTI usually requires long examination times due to the repetitive nature of the acquisition and is very sensitive to motion. These drawbacks have become the largest obstacles to full utilization of DTI. In this work, we propose to overcome these obstacles by using a model-based compressive imaging approach. Our approach consist of models to efficiently represent diffusion-encoded images and the corresponding recovery schemes based on compressive sensing (CS) principles. Our results indicate that the proposed model-based approach can allow reliable recovery of DTI signal from undersampled measurements and outperforms conventional CS recovery.
• Marcellin, M. W., Marcellin, M. W., Bilgin, A., & Altbach, M. I. (2004). Wavelet compression of ECG signals by JPEG2000. In Data Compression Conference, 2004. Proceedings. DCC 2004, 527-527.
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  This paper describes the wavelet compression of ECG signals by JPEG2000. JPEG2000 is the latest international standard for compression of still images. JPEG2000 codec is designed to compress images and it can also be used to compress other signals. The desirable characteristics of the JPEG2000 codec, such as precise rate control and progressive quality, are retained in the presented ECG compression scheme. To compress the ECG data using a JPEG2000 code, the one-dimensional ECG sequence is processed to produce a two-dimensional matrix. This matrix is then encoded using JPEG2000.

Poster Presentations

• Chow, H., Algotar, A., Altbach, M. I., Galons, J., Roe, D., Thomson, C. A., Guillen-Rodriguez, J. M., Martinez, J. A., Chalasani, P., Villa Guillen, D. E., Tapia, E. O., Trujillo, J., Chow, H., Algotar, A., Altbach, M. I., Galons, J., Roe, D., Thomson, C. A., Guillen-Rodriguez, J. M., , Martinez, J. A., et al. (2018, Fall). Abstract: Phase II clinical study of metformin for breast cancer prevention. UACC Scientific Retreat. UACC Scientific Retreat. Tucson, AZ.
• Rosado-Toro, J. A., Avery, R., Altbach, M. I., Rischard, F., & Vanderpool, R. R. (2017, November). Feasibility of MRI-RHC based pressure volume loops in control and PAH patients. AHA Annual Conference. Anahaim, CA: American Heart Association.
• Rosado-Toro, J. A., Avery, R., Altbach, M. I., Abidov, A., & Rodriguez, J. J. (2016, May 7-13). Semi-Automated Segmentation of the Right Ventricle in 4-CH MR Images. ISMRM 24th Annual Meeting & Exhibition. Singapore: Intl. Society for Magnetic Resonance in Medicine.
• Rosado-Toro, J. A., Barr, T., Galons, J., Marron, M. T., Stopeck, A. T., Thomson, C. A., Thompson, P., Carroll, D., Wolf, E., Altbach, M. I., & Rodriguez, J. J. (2015, May 30 – June 5). Automatic Segmentation of Breast Images Using Clustering and Dynamic Programming. ISMRM 23rd Annual Meeting & Exhibition. Toronto, Canada: Intl. Society for Magnetic Resonance in Medicine.