Functional MRI of the human motor cortex using single-shot, multiple gradient-echo spiral imaging

In this study, we combined the advantages of a fast multi-slice spiral imag ing approach with a multiple gradient-echo sampling scheme at high magnetic held strength to improve quantification of BOLD and inflow effects and to estimate T-2* relaxation times in functional brain imaging. Eight echoes ar e collected with echo time (TE) ranging from 5 to 180 ms. Acquisition time per slice and echo time is 25 ms for a nominal resolution of 4 x 4 x 4 mm(3 ). Evaluation of parameter images during rest and stimulation yields no sig nificant activation on the inflow sensitive spin-density images (rho- or I- 0-maps) whereas clear activation patterns in primary human motor cortex (M1 ) and supplementary motor area (SMA) are detected on BOLD sensitive T-2*-ma ps. The calculation of relaxation times and rates of the activated areas ov er all subjects yields an average T-2* + standard deviation (SD) of 46.1 +/ - 4.5 ms (R-2* of 21.8 +/- 2.2 s(-1)) and an average increase (Delta T-2* /- SD) of 0.93 +/- 0.47 ms (Delta R-2(*) of -0.4 +/- 0.14 s(-1)). Our findi ngs demonstrate the usefulness of a multiple gradient echo data acquisition approach in separating various vascular contributions to brain activation in fMRI, (C) 1999 Elsevier Science Inc.