Functional neuroimaging of a complex motor task: Comparison of spin- echo functional MRI, gradient-echo functional MRI and PET

Brain activation of cortical and subcortical foci during a complex motor task as demonstrated with spin-echo (SE) and gradient-echo (GE) FMRI and PET were compared in order to determine how signal changes in each of these FMRI techniques reflect cerebral blood flow changes shown by PET. Five normal volunteers performed bilateral fingering tapping in a defined sequential pattern during functional imaging. BOLD FMRI was performed at 1.5T. Five 32 second activation periods were alternated with five 32 second rest periods. MR signal detection was done by performing a least-squares fit of the time series data to a boxcar function. PET CBF measurements were performed using intravenous H₂¹⁵O. 4 pairs of control and task scans were obtained. PET activation maps were generated by subtracting the averaged activation and control scans. The statistical significance of regions of interest in sensorimotor cortex, basal ganglia and cerebellum for all three techniques were evaluated within each subject. GE-FMRI and SE-FMRI showed large amplitude (p<0.001) signal increases in regions of sensorimotor cortex, basal ganglia and cerebellum. PET also showed significant (p≤0.01) increases in CBF in sensorimotor cortex and cerebellum but less significant increases in CBF in the basal ganglia (p<0.16). The regions of cortical activation shown by SE-FMRI were smaller in size than those shown by GE-FMRI and corresponded more closely to the areas of increased CBF shown by PET. Both GE-FMRI and SE- FMRI are more sensitive for activation by this complex motor task along the entire motor pathway compared to H₂¹⁵O PET. SE-FMRI localizes areas of cortical activation more focally and corresponds more closely to areas of increased CBF on PET than does GE-FMRI.