Early changes in water diffusion, perfusion, T-1, and T-2 during focal cerebral ischemia in the rat studied at 8.5 T

The time evolution of water diffusion, perfusion, T-1, and T-2 is investiga ted at high magnetic field (8.5 T) following permanent middle cerebral arte ry occlusion in the rat. Cerebral blood flow maps were obtained using arter ial spin tagging. although the quantitative perfusion measurements in ische mic tissue still pose difficulties, the combined perfusion and diffusion da ta nevertheless distinguish between a "moderately affected area," with redu ced perfusion but normal diffusion; and a "severely affected area," in whic h both perfusion and diffusion are significantly reduced. Two novel magneti c resonance imaging observations are reported, namely, a decrease in T-2 an d an increase in T-1, both within the first few minutes of ischemia. The ra pid initial decrease in T-2 is believed to be associated with an increase i n deoxyhemoglobin levels, while the initial increase in T-1 may be related to several factors, such as flow effects, an alteration in tissue oxygenati on, and changes in water environment. Magn Reson Med 41:479-485, 1999. (C) 1999 Wiley-Liss, Inc.