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ACCELERATED CHEMICAL SHIFT ENCODED WATER-FAT IMAGING
by
Samir D. Sharma
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(ELECTRICAL ENGINEERING)
May 2012
Copyright 2012 Samir D. Sharma
Object Description
| Title | Accelerated chemical shift encoded water-fat imaging |
| Author | Sharma, Samir D. |
| Author email | sdsharma@usc.edu;samirdsharma@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Electrical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2012-03-06 |
| Date submitted | 2012-04-21 |
| Date approved | 2012-04-23 |
| Restricted until | 2012-04-23 |
| Date published | 2012-04-23 |
| Advisor (committee chair) | Nayak, Krishna S. |
| Advisor (committee member) |
Ortega, Antonio Tjan, Bosco |
| Abstract | Water-fat imaging techniques are commonly used in the research and clinical setting to separate and/or quantitate the two species. Within this class of techniques, chemical shift encoded methods have recently gained significant interest because of their insensitivity to magnetic field inhomogeneity. ❧ The benefits of chemical shift encoding come at a cost of a long scan time because data must be acquired at multiple echo times. This cost increases the likelihood of image artifacts that result from patient motion during the scan while also reducing the overall level of patient comfort. The long scan time becomes especially problematic when imaging non-stationary regions of the body such as the abdomen. In these cases, a compromise with other parameters must be made. Most often, a sacrifice of the spatial resolution and/or volume coverage is required to avoid motion-related image artifacts. ❧ The objective of this dissertation is to present a new method for chemical shift encoded water-fat separation and quantitation from an accelerated data acquisition. In this context, accelerating the acquisition implies that a fewer number of measurements are acquired as compared to the requirements from the Nyquist Sampling Theorem. The resulting image recovery is an ill-posed inverse problem that requires the incorporation of additional knowledge to find the desired solution. A combined parallel imaging and compressed sensing approach for accelerated water-fat separation and quantitation is introduced. To enable this work, I developed a novel method for B0 field map estimation as an alternative to traditional region-growing and region-merging schemes. Uniform water-fat separation is demonstrated in a variety of anatomies from both retrospectively and prospectively undersampled acquisitions. In addition, accurate quantitation is presented in water-fat phantoms as well as in liver datasets acquired from seven subjects. |
| Keyword | water-fat MRI; chemical shift encoding; multiscale B-splines; compressed sensing; parallel imaging |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m |
| Rights | Sharma, Samir D. |
| Access conditions | The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given. |
| Repository name | University of Southern California Digital Library |
| Repository address | USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA |
| Repository email | cisadmin@usc.edu |
| Archival file | uscthesesreloadpub_Volume4/etd-SharmaSami-626-0.pdf |
Description
| Title | Page 1 |
| Full text | ACCELERATED CHEMICAL SHIFT ENCODED WATER-FAT IMAGING by Samir D. Sharma A Dissertation Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (ELECTRICAL ENGINEERING) May 2012 Copyright 2012 Samir D. Sharma |
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