Yujie Qiu

Abstract

Multi-center functional MRI (fMRI) research studies are advantageous but unavoidably introduce variations in the results due to differences in imager vendor, magnetic field strength, imaging pulse sequences, and many other aspects. These variations make combining data from different MRI centers risky. Even for a single MRI center, temporal variations over the course of a study can make combining data problematic. Therefore, it is necessary in both situations to perform quality assurance (QA) measurements on a regular basis. Unfortunately, there are no dynamic standards or phantoms as they are called in the MRI community, which can mimic the small, rapidly changing fMRI signal at a relatively large field-of-view (FOV) and number of magnetic field strengths. The goal of this research was to develop a dynamic phantom which mimiced the signal change in fMRI and hence could be used for QA procedures related to fMRI. A phantom was developed with a rapidly switchable MRI signal. This phantom consisted of a geometric grid, eight vials with solutions of known proton spin-spin relaxation time (T2) values, and a cylindrical electrical cell filled with a polar liquid, all surrounded by water. An electrical circuit was built to interface the phantom to an imager through the pulse sensor and produce pulsed electric (E) fields during the imaging sequence. The results of spin-echo, echo planar imaging (SE-EPI) imaging sequence showed that the signal changed by approximately 8% with the application of a 11.8 kV/m electric field. This change was found to be based on the residual dipolar couplings induced by the applied E field, directly related to the size of the field, and switchable in 50 μs.

Library of Congress Subject Headings

Magnetic resonance imaging--Standards

Publication Date

8-11-2013

Document Type

Dissertation

Student Type

Graduate

Department, Program, or Center

Chester F. Carlson Center for Imaging Science (COS)

Advisor

Hornak, Joseph

Comments

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in December 2013. Physical copy available from RIT's Wallace Library at QC762.6.M34 Q48 2013

Campus

RIT – Main Campus

Plan Codes

IMGS-PHD

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