Inflow versus deoxyhemoglobin effects in BOLD functional MRI using gradient echoes at 1.5 T.

Modified gradient-echo MR techniques were applied to study the effects of inflow on functional brain imaging studies using visual and motor cortex stimulation. The results demonstrate that the large signal changes, seen in previously reported gradient-echo studies at 1.5-2.0 T, are dominated by direct inflow effects, in particular when using a large flip angle and a thin slice. The findings suggest that inflow-based functional imaging, along with Blood Oxygenation Level Dependent (BOLD) functional MRI, may play an important role in future research towards the functional organization of the human brain.