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Incorporation of phase changes in functional magnetic resonance imaging


Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/10323

Incorporation of phase changes in functional magnetic resonance imaging

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Title: Incorporation of phase changes in functional magnetic resonance imaging
Author: Arja, Sunil Kumar
Advisor(s): Calhoun, Vince D
Committee Member(s): Kiehl, Kent
Pattichis, Marios
Department: University of New Mexico. Dept. of Electrical and Computer Engineering
Subject: complex fmri
phase fmri
motor tapping
phase activations
LC Subject(s): Brain--Magnetic resonance imaging--Data processing.
Degree Level: Masters
Abstract: Functional magnetic resonance imaging (fMRI) data is acquired as a complex image pair including magnitude and phase information. The vast majority of fMRI experiments do not attempt to take advantage of the time varying phase information. The phase of the MRI signal is related to the local magnetic field changes, suggesting it may contain useful information about the source of hemodynamic activity. Analysis of phase data acquired from different fMRI experiments has shown the presence of activity in response to various stimuli. However, there have been no studies which have examined phase data in a larger group of subjects for multiple types of fMRI tasks, nor have studies examined phase changes due to event-related stimuli. In this thesis, we examine the magnitude and phase changes in group data in a block-design motor tapping task and in an event-related auditory oddball task. We also look at any additional processing steps that might be required for phase. The results for both block-design and event-related tasks indicate the presence of task related information in the phase data with phase only and magnitude only approaches showing signal changes in the expected brain regions. Techniques like temporal smoothing and Gaussian smoothing seem to help improve the results. Although there is more overall activity detected with magnitude data, the phase only analysis also reveals activity in regions expected to be involved in the task, but not significantly activated in the magnitude only analysis, suggesting that the phase might provide some unique information. In addition, the phase can potentially increase sensitivity within regions also showing magnitude changes. Future work should focus on additional methods for combining the magnitude and phase data.
Graduation Date: December 2009
URI: http://hdl.handle.net/1928/10323

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