IDENTIFICATION OF VASCULAR STRUCTURES AS A MAJOR SOURCE OF SIGNAL CONTRAST IN HIGH-RESOLUTION 2D AND 3D FUNCTIONAL ACTIVATION IMAGING OF THE MOTOR CORTEX AT 1.5T - PRELIMINARY-RESULTS

We have measured the T2 signal response associated with cortical acti vation due to finger motion at 1.5 Tesla. Both thin slice 2D and 3D im ages show signal intensity changes which vary from 2% to 32% depending on volunteer, echo time, slice thickness, and in-plane resolution. Th e largest signal change occurred for the thinnest slices and highest r esolution (2 mm3). This is consistent with reducing partial volume eff ects and a simple difference in phase between the intravascular signal and surrounding parenchyma. No inflow enhancement, was seen on the 2D or 3D scans, confirming the nature of the signal difference for this approach was due to local field inhomogeneity effects. Using 3D imagin g, multiple effects can be seen simultaneously. With a 3D MRA method, it was possible to locate the vessel that was the source of the T2 be havior; it was in each case a vein on the surface of the cortical pare nchyma.