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Assessment of Cerebral Blood Flow Reserve with Xenon-Enhanced Computed Tomography in Ischemic Stroke Patients

839 (age 61 ± 13 years, 16 men, 4 women) with clinical and CT signs of ischemic stroke were examined. They included 14 patients in the chronic stage (more than one month after onset) and four patients in the subacute stage within 48 hours of onset) with stenosis or occlusion of the internal carotid artery. Patients with severe pulmonary, liver or renal disease and those allergic to sulfa were excluded . Cerebral blood flow (CBF) measurements were taken before and 20 min after intravenous administration of a cerebral vasodilator: acetazolamide (17 mg/kg body weight) using a helical scanner equipped with CBF hardware and software package (XeCT SystemTM, DDP Texas, USA). Spiral scanning was performed using 10 mm / sec table speed (pitch = 1), 80 kVp, and 240 mAs. Four parallel levels of CT scans on the axial plane, slices 10 mm thick, located above the orbito-meatal line, were analysed. At each level 2 baseline and 6 xenon-enhanced images were obtained. The enhanced images were produced by a 4.5 min inhalation of 28% stable xenon in oxygen (figure 1). Regions of interest were placed bilaterally on territories of the Introduction