- Associate Professor, Medical Imaging - (Research Scholar Track)
- Associate Professor, Biomedical Engineering
- Associate Professor, Electrical and Computer Engineering
- Associate Professor, Neurosurgery
Following my Ph.D. that focused on cardiac MRI (coronary), I worked at the Applied Science Laboratory, GE Healthcare as a Senior Scientist for almost 7 years until 2010 when I moved to Stanford and SRI International, where I developed novel techniques for dynamic contrast enhanced imaging, ultra-high field (7T) imaging, pediatric imaging as well as for imaging deep brain structures.
My current research interests are in the area of fast imaging and ultra-high field imaging (7T). Specifically, I have been developing dynamic contrast enhanced (DCE) techniques for imaging of cancer (breast, prostate and liver) using novel k-space acquisition and reconstruction strategies. These methods have also been applied for measurmenet of split renal function in pediatric patients as well as for fast T1 mapping in the brain. I have also been investigating deep brain structures such as the thalamus and hippocampus using novel imaging methods coupled with cutting edge deep-learning based segmentation methods that can delineate subfields for targeting or disease progression. I am extending this work to include imaging of structural and functional connectivity esp. for the thalamus.
- Ph.D. Bioengineering
- University of Washington, Seattle, Seattle, Washington, United States
- Magnetic Resonance Coronary Angiography
- M.S. Bioengineering
- University of Washington, Seattle, Seattle, Washington, United States
- Bachelor of Technlogy Electronics and Communication Engineering
- Indian Institute of Technology, Madras, Chennai, Tamil Nadu, India
- SRI International (2013 - 2015)
- Stanford University, Radiology (2010 - 2015)
- GE Healthcare (Applied Science Laboratory) (2007 - 2010)
- Indian Institute of Science (Electrical Engineering) (2004 - 2007)
- Faculty Seed Grant
- Office of Research and Discovery, UA, Summer 2016
High spatio-temporal resolution dynamic MRI for imaging cancer, renal function and cardiac applications; Structural, structural connectivity and functional connectivity imaging of deep brain structures; Image segmentation; Compressed sensing;
MRI Physics, Biomedical Imaging, Biomedical signal and image processing
Advanced Medical ImagingOPTI 638 (Spring 2021)
Advanced Medical ImagingOPTI 638 (Spring 2019)
Advanced Medical ImagingBME 638 (Spring 2018)
Advanced Medical ImagingOPTI 638 (Spring 2018)
Rsrch Meth Biomed EngrBME 597G (Spring 2018)
Advanced Medical ImagingBME 638 (Spring 2016)
Advanced Medical ImagingOPTI 638 (Spring 2016)
Rsrch Meth Biomed EngrBME 597G (Spring 2016)
- , L. U., , M. B., , N. M., , A. B., & , M. S. (2021). A Contrast Synthesized Thalamic Nuclei Segmentation Scheme using Convolutional Neural Networks.More infoThalamic nuclei have been implicated in several neurological diseases.WMn-MPRAGE images have been shown to provide better intra-thalamic nuclearcontrast compared to conventional MPRAGE images but the additional acquisitionresults in increased examination times. In this work, we investigated 3DConvolutional Neural Network (CNN) based techniques for thalamic nucleiparcellation from conventional MPRAGE images. Two 3D CNNs were developed andcompared for thalamic nuclei parcellation using MPRAGE images: a) a nativecontrast segmentation (NCS) and b) a synthesized contrast segmentation (SCS)using WMn-MPRAGE images synthesized from MPRAGE images. We trained the twosegmentation frameworks using MPRAGE images (n=35) and thalamic nuclei labelsgenerated on WMn-MPRAGE images using a multi-atlas based parcellationtechnique. The segmentation accuracy and clinical utility were evaluated on acohort comprising of healthy subjects and patients with alcohol use disorder(AUD) (n=45). The SCS network yielded higher Dice scores in the Medialgeniculate nucleus (P=.003) and Centromedian nucleus (P=.01) with lower volumedifferences for Ventral anterior (P=.001) and Ventral posterior lateral (P=.01)nuclei when compared to the NCS network. A Bland-Altman analysis revealedtighter limits of agreement with lower coefficient of variation between truevolumes and those predicted by the SCS network. The SCS network demonstrated asignificant atrophy in Ventral lateral posterior nucleus in AUD patientscompared to healthy age-matched controls (P=0.01), agreeing with previousstudies on thalamic atrophy in alcoholism, whereas the NCS network showedspurious atrophy of the Ventral posterior lateral nucleus. CNN-based contrastsynthesis prior to segmentation can provide fast and accurate thalamic nucleisegmentation from conventional MPRAGE images.[Journal_ref: ]
- Datta, R., Bacchus, M. K., Kumar, D., Elliott, M. A., Rao, A., Dolui, S., Reddy, R., Banwell, B. L., & Saranathan, M. (2020). Fast automatic segmentation of thalamic nuclei from MP2RAGE acquisition at 7 Tesla. Magnetic resonance in medicine.More infoThalamic nuclei are largely invisible in conventional MRI due to poor contrast. Thalamus Optimized Multi-Atlas Segmentation (THOMAS) provides automatic segmentation of 12 thalamic nuclei using white-matter-nulled (WMn) Magnetization Prepared Rapid Gradient Echo (MPRAGE) sequence at 7T, but increases overall scan duration. Routinely acquired, bias-corrected Magnetization Prepared 2 Rapid Gradient Echo (MP2RAGE) sequence yields superior tissue contrast and quantitative T1 maps. Application of THOMAS to MP2RAGE has been investigated in this study.
- Gravbrot, N., Burket, A., Saranathan, M., & Kasoff, W. S. (2020). Asleep Deep Brain Stimulation of the Nucleus Ventralis Intermedius for Essential Tremor Using Indirect Targeting and Interventional Magnetic Resonance Imaging: Single-Institution Case Series. Movement disorders clinical practice, 7(5), 521-530.More infoLiterature on asleep deep brain stimulation (DBS) of the ventralis intermedius (Vim) nucleus in essential tremor is relatively sparse. Furthermore, controversy exists as to whether indirect ("consensus" or "atlas-based") targeting of the Vim requires physiologic adjustment for effective clinical outcomes in DBS surgery.
- Gravbrot, N., Saranathan, M., Nagae, L. M., Becker, J., & Kasoff, W. S. (2020). Safety Profile of Infinity Deep Brain Stimulation Electrode Placement in a 1.5T Interventional MRI Suite: Consecutive Single-Institution Case Series. AJNR. American journal of neuroradiology, 41(12), 2257-2262.More info"Asleep" deep brain stimulation using general anesthesia and intraoperative MR imaging guidance is considered "off-label" use by current FDA guidelines but is widely used in neurosurgical practice, and excellent safety has been demonstrated using first-generation, omnidirectional electrodes. Safety data for second-generation, directional electrodes in the interventional MR imaging environment have not yet been published. Herein, we report 34 cases of asleep deep brain stimulation using second-generation, directional electrodes in an interventional MR imaging suite at a single institution. Procedural complications and imaging data are described. All patients underwent postoperative MR imaging with fully implanted ("internalized") electrodes after scalp closure; 4 patients also underwent MR imaging with "externalized" electrodes before scalp closure. No MR imaging-related complications were observed, and procedural complication rates were comparable to prior series. This suggests that the use of second-generation, directional electrodes in the interventional MR imaging environment appears to be safe when following manufacturer-published imaging guidelines.
- Gravbrot, N., Saranathan, M., Pouratian, N., & Kasoff, W. S. (2020). Advanced Imaging and Direct Targeting of the Motor Thalamus and Dentato-Rubro-Thalamic Tract for Tremor: A Systematic Review. Stereotactic and functional neurosurgery, 98(4), 220-240.More infoDirect targeting methods for stereotactic neurosurgery in the treatment of essential tremor have been the subject of active research over the past decade but have not yet been systematically reviewed. We present a clinically oriented topic review based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses Group guidelines. Our focus is studies using advanced magnetic resonance imaging (MRI) techniques (ultrahigh-field structural MRI, diffusion-weighted imaging, diffusion-tensor tractography, and functional MRI) for patient specific, in vivo identification of the ventral intermediate nucleus and the dentato-rubro-thalamic tract.
- Honnorat, N., Saranathan, M., Sullivan, E. V., Pfefferbaum, A., Pohl, K. M., & Zahr, N. M. (2021). Performance ramifications of abnormal functional connectivity of ventral posterior lateral thalamus with cerebellum in abstinent individuals with Alcohol Use Disorder. Drug and alcohol dependence, 220, 108509.More infoThe extant literature supports the involvement of the thalamus in the cognitive and motor impairment associated with chronic alcohol consumption, but clear structure/function relationships remain elusive. Alcohol effects on specific nuclei rather than the entire thalamus may provide the basis for differential cognitive and motor decline in Alcohol Use Disorder (AUD). This functional MRI (fMRI) study was conducted in 23 abstinent individuals with AUD and 27 healthy controls to test the hypothesis that functional connectivity between anterior thalamus and hippocampus would be compromised in those with an AUD diagnosis and related to mnemonic deficits. Functional connectivity between 7 thalamic structures [5 thalamic nuclei: anterior ventral (AV), mediodorsal (MD), pulvinar (Pul), ventral lateral posterior (VLP), and ventral posterior lateral (VPL); ventral thalamus; the entire thalamus] and 14 "functional regions" was evaluated. Relative to controls, the AUD group exhibited different VPL-based functional connectivity: an anticorrelation between VPL and a bilateral middle temporal lobe region observed in controls became a positive correlation in the AUD group; an anticorrelation between the VPL and the cerebellum was stronger in the AUD than control group. AUD-associated altered connectivity between anterior thalamus and hippocampus as a substrate of memory compromise was not supported; instead, connectivity differences from controls selective to VPL and cerebellum demonstrated a relationship with impaired balance. These preliminary findings support substructure-level evaluation in future studies focused on discerning the role of the thalamus in AUD-associated cognitive and motor deficits.
- Iglehart, C., Monti, M., Cain, J., Tourdias, T., & Saranathan, M. (2020). A systematic comparison of structural-, structural connectivity-, and functional connectivity-based thalamus parcellation techniques. Brain structure & function, 225(5), 1631-1642.More infoThe thalamus consists of several histologically and functionally distinct nuclei increasingly implicated in brain pathology and important for treatment, motivating the need for development of fast and accurate thalamic parcellation. The contrast between thalamic nuclei as well as between the thalamus and surrounding tissues is poor in T1- and T2-weighted magnetic resonance imaging (MRI), inhibiting efforts to date to segment the thalamus using standard clinical MRI. Automatic parcellation techniques have been developed to leverage thalamic features better captured by advanced MRI methods, including magnetization prepared rapid acquisition gradient echo (MP-RAGE), diffusion tensor imaging (DTI), and resting-state functional MRI (fMRI). Despite operating on fundamentally different image contrasts, these methods claim a high degree of agreement with the Morel stereotactic atlas of the thalamus. However, no comparison has been undertaken to compare the results of these disparate parcellation methods. We have implemented state-of-the-art structural-, diffusion-, and functional imaging-based thalamus parcellation techniques and used them on a single set of subjects. We present the first systematic qualitative and quantitative comparison of these methods. The results show that DTI parcellation agrees more with structural parcellation in the larger thalamic nuclei, while rsfMRI parcellation agrees more with structural parcellation in the smaller nuclei. Structural parcellation is the most accurate in the delineation of small structures such as the habenular, antero-ventral, and medial geniculate nuclei.
- Majdi, M. S., Keerthivasan, M. B., Rutt, B. K., Zahr, N. M., Rodriguez, J. J., & Saranathan, M. (2020). Automated thalamic nuclei segmentation using multi-planar cascaded convolutional neural networks. Magnetic resonance imaging, 73, 45-54.More infoTo develop a fast and accurate convolutional neural network based method for segmentation of thalamic nuclei.
- Su, J. H., Choi, E. Y., Tourdias, T., Saranathan, M., Halpern, C. H., Henderson, J. M., Pauly, K. B., Ghanouni, P., & Rutt, B. K. (2020). Improved Vim targeting for focused ultrasound ablation treatment of essential tremor: A probabilistic and patient-specific approach. Human brain mapping, 41(17), 4769-4788.More infoMagnetic resonance-guided focused ultrasound (MRgFUS) ablation of the ventral intermediate (Vim) thalamic nucleus is an incisionless treatment for essential tremor (ET). The standard initial targeting method uses an approximate, atlas-based stereotactic approach. We developed a new patient-specific targeting method to identify an individual's Vim and the optimal MRgFUS target region therein for suppression of tremor. In this retrospective study of 14 ET patients treated with MRgFUS, we investigated the ability of WMnMPRAGE, a highly sensitive and robust sequence for imaging gray matter-white matter contrast, to identify the Vim, FUS ablation, and a clinically efficacious region within the Vim in individual patients. We found that WMnMPRAGE can directly visualize the Vim in ET patients, segmenting this nucleus using manual or automated segmentation capabilities developed by our group. WMnMPRAGE also delineated the ablation's core and penumbra, and showed that all patients' ablation cores lay primarily within their Vim segmentations. We found no significant correlations between standard ablation features (e.g., ablation volume, Vim-ablation overlap) and 1-month post-treatment clinical outcome. We then defined a group-based probabilistic target, which was nonlinearly warped to individual brains; this target was located within the Vim for all patients. The overlaps between this target and patient ablation cores correlated significantly with 1-month clinical outcome (r = -.57, p = .03), in contrast to the standard target (r = -.23, p = .44). We conclude that WMnMPRAGE is a highly sensitive sequence for segmenting Vim and ablation boundaries in individual patients, allowing us to find a novel tremor-associated center within Vim and potentially improving MRgFUS treatment for ET.
- Witte, M. H., Galons, J., Saranathan, M., Kalb, B. T., Mustacich, D., Moedano, L., & Seckeler, M. (2020). Non contrast MR lymphography of rare lymphatic abnormalities. Lymphology, 53(3), 133-137.
- Altbach, M. I., Bilgin, A., Martin, D. R., Weinkauf, C. C., Fu, Z., Saranathan, M., Johnson, K., & Keerthivasan, M. B. (2019). An Efficient 3D Stack-of-Stars TSE Pulse Sequence for Simultaneous T2-weighted Imaging and T2 Mapping. Magnetic Resonance in Medicine, 82(1), 326-341.
- Bisla, J. K., Saranathan, M., Martin, D. R., Arif-Tiwari, H., & Kalb, B. T. (2019). MR Imaging Evaluation of the Kidneys in Patients with Reduced Kidney Function: Noncontrast Techniques Versus Contrast-Enhanced Techniques. Magnetic resonance imaging clinics of North America, 27(1), 45-57.More infoMR imaging has been optimized for the evaluation of a multitude of disease processes affecting the kidneys. A wide variety of noncontrast methods are available for the evaluation of both kidney structure and function, which are especially useful in clinical scenarios that obviate the use of intravenous contrast. Contrast-enhanced methods remain important, especially for tumor evaluation, and are used increasingly for functional analysis of quantitative biometrics, such as glomerular filtration rate and kidney blood flow.
- 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.More infoTo design a pulse sequence for efficient 3D T2-weighted imaging and T2 mapping.
- Planche, V., Su, J. H., Mournet, S., Saranathan, M., Dousset, V., Han, M., Rutt, B. K., & Tourdias, T. (2019). White-matter-nulled MPRAGE at 7T reveals thalamic lesions and atrophy of specific thalamic nuclei in multiple sclerosis. Multiple sclerosis (Houndmills, Basingstoke, England), 1352458519828297.More infoInvestigating the degeneration of specific thalamic nuclei in multiple sclerosis (MS) remains challenging.
- Su, J. H., Thomas, F. T., Kasoff, W. S., Tourdias, T., Choi, E. Y., Rutt, B. K., & Saranathan, M. (2019). Thalamus Optimized Multi Atlas Segmentation (THOMAS): fast, fully automated segmentation of thalamic nuclei from structural MRI. NeuroImage, 194, 272-282.More infoThe thalamus and its nuclei are largely indistinguishable on standard T1 or T2 weighted MRI. While diffusion tensor imaging based methods have been proposed to segment the thalamic nuclei based on the angular orientation of the principal diffusion tensor, these are based on echo planar imaging which is inherently limited in spatial resolution and suffers from distortion. We present a multi-atlas segmentation technique based on white-matter-nulled MP-RAGE imaging that segments the thalamus into 12 nuclei with computation times on the order of 10 min on a desktop PC; we call this method THOMAS (THalamus Optimized Multi Atlas Segmentation). THOMAS was rigorously evaluated on 7T MRI data acquired from healthy volunteers and patients with multiple sclerosis by comparing against manual segmentations delineated by a neuroradiologist, guided by the Morel atlas. Segmentation accuracy was very high, with uniformly high Dice indices: at least 0.85 for large nuclei like the pulvinar and mediodorsal nuclei and at least 0.7 even for small structures such as the habenular, centromedian, and lateral and medial geniculate nuclei. Volume similarity indices ranged from 0.82 for the smaller nuclei to 0.97 for the larger nuclei. Volumetry revealed that the volumes of the right anteroventral, right ventral posterior lateral, and both right and left pulvinar nuclei were significantly lower in MS patients compared to controls, after adjusting for age, sex and intracranial volume. Lastly, we evaluated the potential of this method for targeting the Vim nucleus for deep brain surgery and focused ultrasound thalamotomy by overlaying the Vim nucleus segmented from pre-operative data on post-operative data. The locations of the ablated region and active DBS contact corresponded well with the segmented Vim nucleus. Our fast, direct structural MRI based segmentation method opens the door for MRI guided intra-operative procedures like thalamotomy and asleep DBS electrode placement as well as for accurate quantification of thalamic nuclear volumes to follow progression of neurological disorders.
- Sullivan, E. V., Zahr, N. M., Saranathan, M., Pohl, K. M., & Pfefferbaum, A. (2019). Convergence of three parcellation approaches demonstrating cerebellar lobule volume deficits in Alcohol Use Disorder. NeuroImage. Clinical, 24, 101974.More infoRecent advances in robust and reliable methods of MRI-derived cerebellar lobule parcellation volumetry present the opportunity to assess effects of Alcohol Use Disorder (AUD) on selective cerebellar lobules and relations with indices of nutrition and motor functions. In pursuit of this opportunity, we analyzed high-resolution MRI data acquired in 24 individuals with AUD and 20 age- and sex-matched controls with a 32-channel head coil using three different atlases: the online automated analysis pipeline volBrain Ceres, SUIT, and the Johns Hopkins atlas. Participants had also completed gait and balance examination and hematological analysis of nutritional and liver status, enabling testing of functional meaningfulness of each cerebellar parcellation scheme. Compared with controls, each quantification approach yielded similar patterns of group differences in regional volumes: All three approaches identified AUD-related deficits in total tissue and total gray matter, but only Ceres identified a total white matter volume deficit. Convergent volume differences occurred in lobules I-V, Crus I, VIIIB, and IX. Coefficients of variation (CVs) were
- Zahr, N. M., Pohl, K. M., Saranathan, M., Sullivan, E. V., & Pfefferbaum, A. (2019). Hippocampal subfield CA2+3 exhibits accelerated aging in Alcohol Use Disorder: A preliminary study. NeuroImage. Clinical, 22, 101764.More infoThe profile of brain structural dysmorphology of individuals with Alcohol Use Disorders (AUD) involves disruption of the limbic system. In vivo imaging studies report hippocampal volume loss in AUD relative to controls, but only recently has it been possible to articulate different regions of this complex structure. Volumetric analysis of hippocampal regions rather than total hippocampal volume may augment differentiation of disease processes. For example, damage to hippocampal subfield cornu ammonis 1 (CA1) is often reported in Alzheimer's disease (AD), whereas deficits in CA4/dentate gyrus are described in response to stress and trauma. Two previous studies explored the effects of chronic alcohol use on hippocampal subfields: one reported smaller volume of the CA2+3 in alcohol-dependent subjects relative to controls, associated with years of alcohol consumption; the other, smaller volumes of presubiculum, subiculum, and fimbria in alcohol-dependent relative to control men. The current study, conducted in 24 adults with DSM5-diagnosed AUD (7 women, 53.7 ± 8.8) and 20 controls (7 women, 54.1 ± 9.3), is the first to use FreeSurfer 6.0, which provides state-of-the art hippocampal parcellation, to explore the sensitivity of hippocampal sufields to alcoholism. T1- and T2- images were collected on a GE MR750 system with a 32-channel Nova head coil. FreeSurfer 6.0 hippocampal subfield analysis produced 12 subfields: parasubiculum; presubiculum; subiculum; CA1; CA2+3; CA4; GC-ML-DG (Granule Cell (GC) and Molecular Layer (ML) of the Dentate Gyrus (DG)); molecular layer; hippocampus-amygdala-transition-area (HATA); fimbria; hippocampal tail; hippocampal fissure; and whole volume for left and right hippocampi. A comprehensive battery of neuropsychological tests comprising attention, memory and learning, visuospatial abilities, and executive functions was administered. Multiple regression analyses of raw volumetric data for each subfields by group, age, sex, hemisphere, and supratentorial volume (svol) showed significant effects of svol (p
- Zahr, N. M., Sullivan, E. V., Pohl, K. M., Pfefferbaum, A., & Saranathan, M. (2019). Sensitivity of ventrolateral posterior thalamic nucleus to back pain in alcoholism and CD4 nadir in HIV. Human brain mapping.More infoVolumes of thalamic nuclei are differentially affected by disease-related processes including alcoholism and human immunodeficiency virus (HIV) infection. This MRI study included 41 individuals diagnosed with alcohol use disorders (AUD, 12 women), 17 individuals infected with HIV (eight women), and 49 healthy controls (24 women) aged 39 to 75 years. A specialized, high-resolution acquisition protocol enabled parcellation of five thalamic nuclei: anterior [anterior ventral (AV)], posterior [pulvinar (Pul)], medial [mediodorsal (MD)], and ventral [including ventral lateral posterior (VLp) and ventral posterior lateral (VPl)]. An omnibus mixed-model approach solving for volume considered the "fixed effects" of nuclei, diagnosis, and their interaction while covarying for hemisphere, sex, age, and supratentorial volume (svol). The volume by diagnosis interaction term was significant; the effects of hemisphere and sex were negligible. Follow-up mixed-model tests thus evaluated the combined (left + right) volume of each nucleus separately for effects of diagnosis while controlling for age and svol. Only the VLp showed diagnoses effects and was smaller in the AUD (p = .04) and HIV (p = .0003) groups relative to the control group. In the AUD group, chronic back pain (p = .008) and impaired deep tendon ankle reflex (p = .0005) were associated with smaller VLp volume. In the HIV group, lower CD4 nadir (p = .008) was associated with smaller VLp volume. These results suggest that the VLp is differentially sensitive to disease processes associated with AUD and HIV.
- 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.More infoTSE-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.
- Shaikh, J., Stoddard, P. B., Levine, E. G., Roh, A. T., Saranathan, M., Chang, S. T., Muelly, M. C., Hargreaves, B. A., Vasanawala, S. S., & Loening, A. M. (2018). View-Sharing Artifact Reduction With Retrospective Compressed Sensing Reconstruction in the Context of Contrast-Enhanced Liver MRI for Hepatocellular Carcinoma (HCC) Screening. Journal of magnetic resonance imaging : JMRI.More infoView-sharing (VS) increases spatiotemporal resolution in dynamic contrast-enhanced (DCE) MRI by sharing high-frequency k-space data across temporal phases. This temporal sharing results in respiratory motion within any phase to propagate artifacts across all shared phases. Compressed sensing (CS) eliminates the need for VS by recovering missing k-space data from pseudorandom undersampling, reducing temporal blurring while maintaining spatial resolution.
- Levine, E., Daniel, B., Vasanawala, S., Hargreaves, B., & Saranathan, M. (2017). 3D Cartesian MRI with compressed sensing and variable view sharing using complementary poisson-disc sampling. Magnetic resonance in medicine.More infoTo enable robust, high spatio-temporal-resolution three-dimensional Cartesian MRI using a scheme incorporating a novel variable density random k-space sampling trajectory allowing flexible and retrospective selection of the temporal footprint with compressed sensing (CS).
- Loening, A. M., Litwiller, D. V., Saranathan, M., & Vasanawala, S. S. (2017). Increased Speed and Image Quality for Pelvic Single-Shot Fast Spin-Echo Imaging with Variable Refocusing Flip Angles and Full-Fourier Acquisition. Radiology, 561-568.More infoPurpose To assess image quality and speed improvements for single-shot fast spin-echo (SSFSE) with variable refocusing flip angles and full-Fourier acquisition (vrfSSFSE) pelvic imaging via a prospective trial performed in the context of uterine leiomyoma evaluation. Materials and Methods Institutional review board approval and informed consent were obtained. vrfSSFSE and conventional SSFSE sagittal and coronal oblique acquisitions were performed in 54 consecutive female patients referred for 3-T magnetic resonance (MR) evaluation of known or suspected uterine leiomyomas. Two radiologists who were blinded to the image acquisition technique semiquantitatively scored images on a scale from -2 to 2 for noise, image contrast, sharpness, artifacts, and perceived ability to evaluate uterine, ovarian, and musculoskeletal structures. The null hypothesis of no significant difference between pulse sequences was assessed with a Wilcoxon signed rank test by using a Holm-Bonferroni correction for multiple comparisons. Results Because of reductions in specific absorption rate, vrfSSFSE imaging demonstrated significantly increased speed (more than twofold, P < .0001), with mean repetition times compared with conventional SSFSE imaging decreasing from 1358 to 613 msec for sagittal acquisitions and from 1494 to 621 msec for coronal oblique acquisitions. Almost all assessed image quality and perceived diagnostic capability parameters were significantly improved with vrfSSFSE imaging. These improvements included noise, sharpness, and ability to evaluate the junctional zone, myometrium, and musculoskeletal structures for both sagittal acquisitions (mean values of 0.56, 0.63, 0.42, 0.56, and 0.80, respectively; all P values < .0001) and coronal oblique acquisitions (mean values of 0.81, 1.09, 0.65, 0.93, and 1.12, respectively; all P values < .0001). For evaluation of artifacts, there was an insufficient number of cases with differences to allow statistical testing. Conclusion Compared with conventional SSFSE acquisition, vrfSSFSE acquisition increases 3-T imaging speed via reduced specific absorption rate and leads to significant improvements in perceived image quality and perceived diagnostic capability when evaluating pelvic structures. (©) RSNA, 2016 Online supplemental material is available for this article.
- Pandey, A., Yoruk, U., Galons, J., 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.
- 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.More infoTo develop a novel multiresolution MRI methodology for accurate estimation of glomerular filtration rate (GFR) in vivo.
- Saranathan, M., Worters, P. W., Rettmann, D. W., Winegar, B., & Becker, J. (2017). Physics for clinicians: Fluid-attenuated inversion recovery (FLAIR) and double inversion recovery (DIR) Imaging. Journal of magnetic resonance imaging : JMRI, 46(6), 1590-1600.More infoA pedagogical review of fluid-attenuated inversion recovery (FLAIR) and double inversion recovery (DIR) imaging is conducted in this article. The basics of the two pulse sequences are first described, including the details of the inversion preparation and imaging sequences with accompanying mathematical formulae for choosing the inversion time in a variety of scenarios for use on clinical MRI scanners. Magnetization preparation (or T2prep), a strategy for improving image signal-to-noise ratio and contrast and reducing T1 weighting at high field strengths, is also described. Lastly, image artifacts commonly associated with FLAIR and DIR are described with clinical examples, to help avoid misdiagnosis.
- Yoruk, U., Saranathan, M., Loening, A. M., Hargreaves, B. A., & Vasanawala, S. S. (2016). High temporal resolution dynamic MRI and arterial input function for assessment of GFR in pediatric subjects. Magnetic resonance in medicine, 75(3), 1301-11.More infoTo introduce a respiratory-gated high-spatiotemporal-resolution dynamic-contrast-enhanced MRI technique and a high-temporal-resolution aortic input function (HTR-AIF) estimation method for glomerular filtration rate (GFR) assessment in children.
- Clarke, S. E., Saranathan, M., Rettmann, D. W., Hargreaves, B. A., & Vasanawala, S. S. (2015). High resolution multi-arterial phase MRI improves lesion contrast in chronic liver disease. Clinical and investigative medicine. Medecine clinique et experimentale, 38(3), E90-9.More infoTo determine the reliability of arterial phase capture and evaluate hypervascular lesion contrast kinetics with a combined view-sharing and parallel imaging dynamic contrast-enhanced acquisition, DIfferential Sub-sampling with Cartesian Ordering (DISCO), in patients with known chronic liver disease.
- Crombé, A., Saranathan, M., Ruet, A., Durieux, M., de Roquefeuil, E., Ouallet, J. C., Brochet, B., Dousset, V., & Tourdias, T. (2015). MS lesions are better detected with 3D T1 gradient-echo than with 2D T1 spin-echo gadolinium-enhanced imaging at 3T. AJNR. American journal of neuroradiology, 36(3), 501-7.More infoIn multiple sclerosis, gadolinium enhancement is used to classify lesions as active. Regarding the need for a standardized and accurate method for detection of multiple sclerosis activity, we compared 2D-spin-echo with 3D-gradient-echo T1WI for the detection of gadolinium-enhancing MS lesions.
- Hope, T. A., Petkovska, I., Saranathan, M., Hargreaves, B. A., & Vasanawala, S. S. (2015). Combined parenchymal and vascular imaging: High spatiotemporal resolution arterial evaluation of hepatocellular carcinoma. Journal of magnetic resonance imaging : JMRI.More infoTo assess the ability of high-resolution arterial phase imaging of hepatocellular carcinoma (HCC) to provide combined vascular characterization and parenchymal evaluation.
- Loening, A. M., Saranathan, M., Ruangwattanapaisarn, N., Litwiller, D. V., Shimakawa, A., & Vasanawala, S. S. (2015). Increased speed and image quality in single-shot fast spin echo imaging via variable refocusing flip angles. Journal of magnetic resonance imaging : JMRI, 42(6), 1747-58.More infoTo develop and validate clinically a single-shot fast spin echo (SSFSE) sequence utilizing variable flip angle refocusing pulses to shorten acquisition times via reductions in specific absorption rate (SAR) and improve image quality.
- Quist, B., Hargreaves, B. A., Daniel, B. L., & Saranathan, M. (2015). Balanced SSFP Dixon imaging with banding-artifact reduction at 3 Tesla. Magnetic resonance in medicine, 74(3), 706-15.More infoTo develop a three-dimensional (3D) balanced steady-state free-precession (bSSFP) two-point Dixon method with banding-artifact suppression to offer robust high-resolution 3D bright-fluid imaging.
- Ruangwattanapaisarn, N., Loening, A. M., Saranathan, M., Litwiller, D. V., & Vasanawala, S. S. (2015). Faster pediatric 3-T abdominal magnetic resonance imaging: comparison between conventional and variable refocusing flip-angle single-shot fast spin-echo sequences. Pediatric radiology, 45(6), 847-54.More infoSingle-shot fast spin echo (SSFSE) is particularly appealing in pediatric patients because of its motion robustness. However radiofrequency energy deposition at 3 tesla forces long pauses between slices, leading to longer scans, longer breath-holds and more between-slice motion.
- Saranathan, M., Tourdias, T., Bayram, E., Ghanouni, P., & Rutt, B. K. (2015). Optimization of white-matter-nulled magnetization prepared rapid gradient echo (MP-RAGE) imaging. Magnetic resonance in medicine, 73(5), 1786-94.More infoTo optimize the white-matter-nulled (WMn) Magnetization Prepared Rapid Gradient Echo (MP-RAGE) sequence at 7 Tesla (T), with comparisons to 3T.
- Saranathan, M., Rettmann, D. W., Hargreaves, B. A., Lipson, J. A., & Daniel, B. L. (2014). Variable spatiotemporal resolution three-dimensional Dixon sequence for rapid dynamic contrast-enhanced breast MRI. Journal of magnetic resonance imaging : JMRI, 40(6), 1392-9.More infoTo investigate a new variable spatiotemporal resolution dynamic contrast-enhanced (DCE) MRI method termed DIfferential Subsampling with Cartesian Ordering (DISCO), for imaging of breast cancer.
- Saranathan, M., Tourdias, T., Kerr, A. B., Bernstein, J. D., Kerchner, G. A., Han, M. H., & Rutt, B. K. (2014). Optimization of magnetization-prepared 3-dimensional fluid attenuated inversion recovery imaging for lesion detection at 7 T. Investigative radiology, 49(5), 290-8.More infoThe aim of this study was to optimize the 3-dimensional (3D) fluid attenuated inversion recovery (FLAIR) pulse sequence for isotropic high-spatial-resolution imaging of white matter (WM) and cortical lesions at 7 T.
- 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.
- Keerthivasan, M. B., Winegar, B., Udayasankar, U., Bilgin, A., Altbach, M. I., & Saranathan, M. (2018, June). An optimized single-shot sequence for fast T2w imaging of the brain. In ISMRM annual meeting.
- Li, Z., Li, Z., Bilgin, A., Bilgin, A., Johnson, K., Johnson, K., Galons, J., Galons, J., Saranathan, M., Saranathan, M., Martin, D. R., Martin, D. R., Altbach, M. I., & Altbach, M. I. (2018, June). Rapid multi-slice abdominal T1 mapping with IR-radSSFP. 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.
- Keerthivasan, M. B., Altbach, M. I., Altbach, M. I., Saranathan, M., Bilgin, A., Bilgin, A., Galons, J., Martin, D. R., Martin, D. R., Martin, D. R., Galons, J., Galons, J., Bilgin, A., Saranathan, M., Saranathan, M., Keerthivasan, M. B., 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.
- Keerthivasan, M. B., Bilgin, A., Martin, D. R., Becker, J., Altbach, M. I., & Saranathan, M. (2017, May). Clinical utility of a novel ultrafast T2 Weighted sequence for Spine Imaging.. In 25th Annual meeting of ISMRM, 538.
- Keerthivasan, M. B., Saranathan, M., Bilgin, A., Martin, D. R., & Altbach, M. I. (2017, May). High-resolution 3D T2 mapping using a stack-of-stars radial FSE pulse sequence. In 25th Annual meeting of ISMRM, 3957.
- Pandey, A., Galons, J., Johnson, K., Martin, D. R., Altbach, M. I., Bilgin, A., & Saranathan, M. (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.
- Pandey, A., Min, C., Li, Z., Johnson, K., Steyn, L., Purvis, W., Harland, R. C., Pappas, K. K., Sharma, P., Martin, D. R., Saranathan, M., & Galons, J. (2017, May). An MR compatible kidney perfusion system to assess kidney function and organ preservation. In 25th Annual meeting of ISMRM, 816.
- Thomas, F. T., Su, J., Rutt, B. K., & Saranathan, M. (2017, May). A method for near-realtime automated segmentation of thalamic nuclei.. In 25th Annual meeting of ISMRM, 4736.
- Zahr, N. M., & Saranathan, M. (2017, May). Substructural volumes of the thalmus in alcoholism. In 25th Annual meeting of ISMRM, 4214.
- Pandey, A., Yoruk, U., Sharma, P., Martin, D., Altbach, M., Bilgin, A., & Saranathan, M. (2016, May). Multiresolution Imaging Using Golden Angle Stack-Of-Stars and Compressed Sensing. In ISMRM, 24th Annual Meeting, Singapore.
- Saranathan, M., Sharma, P., Udayasankar, U., & Khan, R. (2016, May). Comparison of a novel, motion-robust MPRAGE imaging sequence with conventional MPRAGE imaging.. In ISMRM, 24th Annual Meeting, Singapore.
- Su, J., Tourdias, T., Saranathan, M., Ghanouni, P., & Rutt, B. (2016, May). THOMAS: Thalamus Optimized Multi-Atlas Segmentation at 3T. In ISMRM, 24th Annual Meeting, Singapore.
- Seckeler, M., Moedano, L., Kalb, B. T., Saranathan, M., Galons, J., & Witte, M. H. (2019, September). Non-Contrast MR Lymphology of Rare Central Lymphatic Abnormalities. 27th World Congress of Lymphology 2019. Buenos Aires, Argentina.
- Witte, M. H., Galons, J., Saranathan, M., Kalb, B. T., Moedano, L., & Seckeler, M. (2019, September). Non-Contrast MR Lymphology of Rare Central Lymphatic Abnormalities. International Society of Lymphology XXVII World Congress 2019. Buenos Aires, Argentina.
- Thomas, F., Kasoff, W., & Saranathan, M. (2018, Spring). A novel strategy for automated near-real-time segmentation of the ventral intermediate (Vim) nucleus for deep brain stimulation (DBS) surgery. ISMRM.