Single-shot T*(2) measurement to establish optimum echo time for fMRI: Studies of the visual, motor, and auditory cortices at 3.0 T

The signal change in fMRI is dependent on the echo time and the rate of dec ay of transverse magnetization. The latter factor may vary across regions o f the brain as a result of variations in field homogeneity. Previous measur ements of the signal change with echo time have generally employed relative ly slow multi-echo techniques, which may be sensitive to movement and habit uation effects. Here a fast T-2(*) measurement technique, involving the gen eration of six low-resolution echo planar images from a single FID, is desc ribed, and its use in the evaluation of the optimum echo time for visual, m otor, and auditory fMRI experiments at 3.0 T is outlined. (C) 2001 Wiley-Li ss, Inc.