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Diffusion weighted fMRI at 1.5 T

✍ Scribed by Allen W. Song; Eric C. Wong; Steve G. Tan; James S. Hyde

Publisher
John Wiley and Sons
Year
1996
Tongue
English
Weight
428 KB
Volume
35
Category
Article
ISSN
0740-3194

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✦ Synopsis

Abstract

Functional magnetic resonance imaging (fMRI) is capable of detecting task‐induced blood oxygenation changes using susceptibility sensitive pulse sequences such as gradient‐recalled echo‐planar imaging (EPI). The local signal increases seen in the time course are believed to be due to an increase in oxygen delivery that is incommensurate with oxygen demands. To help isolate the sources of functional signal changes, the authors have incorporated various forms of diffusion weighting Into EPI pulse sequences to characterize the apparent mobility of the functionally modulated protons. Results suggest that the majority of the functional signal at 1.5 T arises from protons that have apparent diffusion coefficients that are approximately four or five times higher than that of brain tissue. This implies that significant functional signal sources are either protons within the vascular space or protons from the perivascular space that is occupied by cerebro‐spinal fluid.

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