Measurement of regional cerebral blood flow by stable xenon-enhanced computed tomography. Part I: Efficacy, normal values and adverse reactions in 40 normal Taiwan Chineses

Background: By sequential computed tomography, nonradioactive xenon gas is inhaled and the temporal changes in radiographic enhancement produced by the inhalation are measured. Methods: Studies involving 5 minutes of mixed gas including 30% stable xenon,30% oxygen and 40% of room air inhalation were performed routinely in 40 awake volunteers and patients. Direct measurement of the expired xenon concentration and the use of computer-programmed formulas allowed accurate, reproducible measurement of regional cerebral blood flow and partition coefficients of small regions. Results: There was no definite significant side-to-side difference. The measurement were: 42.2ml/100g/minute ±6.5 in anterior anterior cerebral artery territory, 42.1ml/100g/minute ±6.2 in middle cerebral artery territory, 38.1ml/100g/minute ±4.3 in posterior cerebral artery territory, 55.5ml/100g/minute ±5.9 in putamen territory, and 61.4ml/100g/minute ±7.3 in thalamus territory. Adverse reactions such as respiratory delay, nausea, vomiting and headache were observed in 22.5% without permanent neurological deficit. Physiologic reactions of xenon gas such as lightheadedness, and emotional lability were found in 35% of patients. All of them became normal within 5 minutes after re-breathing of room-air after the procedures. Conclusion: Measurement of regional cerebral blood flow with xenon-CT is feasible and reproducible. The xenon/CT method appears to have several advantages over conventional cerebral blood flow measurement utilizing radionuclide techniques, and it can provide useful clinical and research information. Cerebral blood flow becomes less with the ages advanced in all the vascular territories in normal Chinese and this is compatible to the previous western reports.