The use of positron emission tomography in cerebrovascular disease

Positron emission tomography (PET) is the only technique that provides accurate, quantitative measurements of regional hemodynamics and metabolism in human subjects. PET measurements are being used to identify high-risk patients who have carotid occlusion for inclusion in a clinical trial to assess the efficacy of surgical revascularization in reducing the subsequence of ipsilateral ischemic stroke. Early studies of recovery from stroke have suggested functional reorganization of the brain, but further investigations with more rigorous experimental design need to be performed. PET has demonstrated that hematomas exert a primary depression of metabolism rather than inducing ischemia in the surrounding tissue. It has also documented the integrity of autoregulation and provided clinically useful information regarding the safety of blood pressure reduction after intracranial hemorrhage. Studies in subarachnoid hemorrhage have differentiated the primary effects of the hemorrhage on cerebral hemodynamics and metabolism from those of vasospasm.