MR perfusion studies with T1-weighted echo planar imaging.

The T1 perfusion model has worked well in brain functional studies where flow changes are measured. Using selective and nonselective inversion pulses, a new method has been developed to study steady-state brain blood flow. The authors obtained flow-sensitive images using selective inversion and flow-insensitive images using nonselective inversion. Subtraction of flow-insensitive images from flow-sensitive images gave us flow-weighted images with good gray-white flow contrast in cortical gray matter as well as in the thalamus and basal ganglia. Fitting T1s of flow-insensitive and flow-sensitive images allowed us to obtain preliminary results of brain blood flow maps. Two specific problems can seriously affect the accuracy of the brain blood flow values and the gray-white flow contrast of brain blood flow maps. These are the problems of the partial volume effect of CSF and gray matter, and the difference between blood T1 and white matter T1. The authors discuss in detail the character of these problems and present a number of approaches to manage such problems.