Browsing by Subject "Whole Body Imaging"
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Item Robust Fat and Fluid Suppression in MR Imaging: Technical Developments and Advanced Clinical Applications(2018-07-25) Wang, Xinzeng; Vinogradov, Elena; Madhuranthakam, Ananth; Lenkinski, Robert; Pedrosa, Ivan; Lewis, Matthew AllenFat and fluid suppression methods are widely used in MR imaging to improve the lesion conspicuity, reduce the artifacts, increase quantification accuracy etc. However, these methods often suffer from either low signal to noise ratio (SNR), incomplete fat suppression or long scan times in some challenging clinical applications, such as MR Neurography, abdominal imaging, whole-body imaging and diffusion-weighted imaging. The research in this thesis aims to improve and develop MR sequences and reconstruction methods for robust fat and fluid suppression in several advanced clinical applications. The first topic of this thesis focuses on improving fat suppression. A frequency offset corrected inversion (FOCI) pulse based short tau inversion recovery (STIR) sequence was developed to improve the fat suppression in brachial plexus imaging, where large B1 and B0 inhomogeneities are often encountered. However, similar to the conventional STIR, it suffers from low SNR. Then, a multi-echo Dixon based variable flip angle TSE sequence was implemented for robust fat suppression with improved SNR and blood suppression, increasing the visualization of brachial plexus. The multi-echo Dixon method was later extended to single shot TSE (SShTSE) sequence to improve the fat suppression in breathhold abdominal imaging, where the commonly used fat suppression method (SPAIR) suffers from incomplete fat suppression due to the large B0 inhomogeneities. The second topic was simultaneous fat and fluid suppression. A dual-echo 3D TSE sequence combined with multi-echo Dixon was developed to generate simultaneous fat and fluid suppressed images of the cervical spines in a single acquisition. It can also simultaneously generate the standard T2-weighted image, fluid suppressed image and myelogram, significantly reducing the total scan time compared to the current clinical protocols. Then a fast whole-body MR imaging (7 min) sequence was developed for metastatic cancer detection by combining the simultaneous fat and fluid suppression method with the SShTSE acquisition. The images generated from the proposed sequence showed good lesion conspicuity without EPI-associated geometric distortions. Finally, the multi-echo Dixon was implemented with the TSE-based diffusion-weighted imaging sequence, to generate distortion-fee diffusion images with improved fat suppression and lesion conspicuity in areas with large B0 inhomogeneities, such as cervical spinal cord.Item Tumor Segmentation of Whole-Body Magnetic Resonance Imaging in Neurofibromatosis Type 1 Patients: Tumor Burden Correlates(2017-01-17) Heffler, Michael A.; Chhabra, Avneesh; Le, Lu Q.; Xi, YinPURPOSE: To use software segmentation of whole body MRI (WBMRI) to quantitate total body tumor volume (tumor burden) in patients with Neurofibromatosis type 1 (NF1) and examine associations between demographic factors and tumor burdens. METHODS: Patients with NF1 underwent WBMRI, and the images were reviewed by a board-certified radiologist for tumors. Each tumor was classified as superficial or internal, and discrete or plexiform. Tumors were then segmented by a trained assistant using a semi-automated software-based tool (SliceOMatic, TomoVision, Québec, Canada). Segmentation times were recorded. Segmentation yielded the total quantity and tumor burden of superficial, internal, and plexiform tumors. Correlations between the segmentation data and patient demographic factors were examined. RESULTS: 15 patients were included (42.3 +/- 13.6 years, 10 female, 5 male). Segmentation time ranged from 20 to 60 minutes, and yielded 2328 tumors (1582 superficial, 746 internal, and 23 plexiform). One tumor (0.04%) was malignant, all others were benign. The number of tumors per patient ranged from 14 to 397. Tumor burden ranged from 6.95 cm3 to 571 cm3. Individual tumor volume ranged from 0.0120 cm3 to 298 cm3. Significant correlation was found between total volume of superficial tumors and height (ρ = 0.5966, p < 0.02). Male patients had larger overall tumor burdens (p < 0.05) and larger superficial tumor burdens (p < 0.03). Patients with a negative family history of NF1 tended to have more tumors (p < 0.05). CONCLUSION: Segmentation of WBMRI in patients with NF1 is possible and can elucidate meaningful relationships between disease phenotype and demographic factors.