Hyperacute stroke: Simultaneous measurement of relative cerebral blood volume, relative cerebral blood flow, and mean tissue transit time

PURPOSE: To investigate additional information provided by maps of relative cerebral blood flow in functional magnetic resonance (MR) imaging of human hyperacute cerebral ischemic stroke. MATERIALS AND METHODS: Diffusion-weighted and hemodynamic MR imaging were p erformed in 23 patients less than 12 hours after the onset of symptoms. Map s of relative cerebral blood flow and tracer mean tissue transit time were computed, as were maps of apparent diffusion and relative cerebral blood vo lume. Acute lesion volumes on the maps were compared with follow-up imaging findings. RESULTS: In 15 of 23 subjects (65%), blood flow maps revealed hemodynamic a bnormalities not visible on blood volume maps. A mismatch between initial b lood flow and diffusion findings predicted growth of infarct more often (12 of 15 subjects with infarcts that grew) than did a mismatch between initia l blood volume and diffusion findings (eight of 15). However, lesion volume s on blood volume and diffusion maps correlated better with eventual infarc t volumes (r > 0.90) than did those on blood flow and tracer mean transit t ime maps (r similar to 0.6), likely as a result of threshold effects. In ei ght patients, blood volume was elevated around the diffusion abnormality, s uggesting a compensatory hemodynamic response. CONCLUSION: MR imaging carl delineate areas of altered blood flow, blood vo lume, and water mobility in hyperacute human stroke. Predictive models of t issue outcome may benefit by including computation of both relative cerebra l blood flow and blood volume.