Diffusion weighted magnetic resonance imaging (DW-MRI) is an imaging technique that provides a measure of local tissue microstructure based on the water molecular diffusion. Although this imaging method has been successfully used in investigating brain white matter for normal and various dysfunctional states, major limitations of this technique have recently been identified. In diffusion tensor MRI (DT-MRI), image noise produces both noise and bias in the estimated tensor, and leads to errors in estimated axonal fiber pathways. Moreover the single-tensor model is inappropriate in regions with non-parallel fiber structure.
Several high angular resolution diffusion imaging (HARDI) methods have been proposed as alternative tools for resolving multiple fiber structures within a single voxel. At low SNR, however, fiber orientation from HARDI becomes unreliable. Also none of the HARDI methods can provide estimates of the intrinsic diffusion properties of any of the fibers. Addressing limitations of this technique, we suggest improved imaging methods for brain white matter in conventional and ultra high field imaging environments.
This study provides experimental and theoretical results about the uncertainty in fiber orientation using DT-MRI. It proposes methods for the estimation of intrinsic diffusion properties as well as reliable fiber orientation distribution (FOD) functions using HARDI with simulations and in vivo experiments. These methods are then applied to ultra high field strength experiments using a field inhomogeneity correction for image distortions. In summary, the results of this study provide improved diffusion imaging methods for human and/or non-human primates.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-07232008-170634 |
| Date | 28 July 2008 |
| Creators | JEONG, HA-KYU |
| Contributors | Zhaohua Ding, Ph. D., Mark D. Does, Ph. D., Bruce M. Damon, Ph. D., John C. Gore, Ph. D., Adam W. Anderson, Ph. D. |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-07232008-170634/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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