Comparing gray and white matter fMRI activation using asymmetric spin echo spiral

Recent developments have shown that it is possible to detect functional magnetic resonance imaging (fMRI) activation in white matter (WM). Enhanced sensitivity to WM fMRI signals has been associated with the asymmetric spin echo (ASE) spiral sequence. The ASE spiral sequence produces three consecutive images that have equal blood-oxygen level-dependent (BOLD) contrast but increasing T2 contrast. The current study evaluated whether ASE spiral sensitivity differed between white and gray matter in the corpus callosum, superior parietal lobes, cingulate gyrus, and inferior frontal lobes. Contrast and noise were compared across the three images for each region. Results showed increasing gains in functional contrast in both white and gray matter as a function of T2 contrast. The third image, with the most T2 contrast, showed the largest increase in contrast, while changes in noise were maintained. The results suggest that ASE spiral increases fMRI sensitivity globally through the addition of T2 weighted contrast.

► fMRI activation was elicited in both gray and white matter regions in the brain. ► We used the ‘asymmetric spin echo’ MRI sequence which increases white matter signals. ► Functional contrast increased in white matter, replicating prior findings. ► This pattern was identical in gray matter, verifying white matter activation. ► ‘Asymmetric spin echo’ enhances fMRI signals globally through increased T2 weighting.