Xenon-induced flow activation in patients with cerebral insult who undergoxenon-enhanced CT blood flow studies

BACKGROUND AND PURPOSE: Stable xenon-enhanced CT (Xe-s/CT) has gained wide acceptance in the assessment of regional cerebral blood flow (rCBF) in pati ents with intracranial abnormalities. The aim of this study was to test whe ther the contrast medium (ie, Xe-s) itself directly induces relevant change s in rCBF, thereby distorting any valid determination of cerebral perfusion by using Xe-s/CT. METHODS: To characterize the degree and temporal dynamics of Xe-s-induced f low activation, a thermal diffusion (TD)-based microprobe was placed subcor tically into the frontal lobe on either hemisphere to assess rCBF (TD-rCBF) continuously in 23 patients (mean age, 55 +/- 18 years) with severe intrac ranial insult who were undergoing Xe-s/CT. RESULTS: In 35, the Xe-s/CT studies TD-rCBF rose from 25 +/- 17 mL/100 g pe r minute (range, 5-42 mL/100 g per minute) before Xe-s administration to 28 +/- 21 mL/100 g per minute (range, 6-46 mL/100 g per minute) after arteria l Xe-s saturation was reached. Analysis of the flow activation curve showed a logarithmic shape with an increase in TD-rCBF between 3% and 7% within t he first 76 seconds of Xe-s wash-in (12% after 190 seconds) and showed no f urther augmentation until the end of the blood flow study. CONCLUSION: The observed Xe-s-induced rCBF activation, which showed signifi cant interand intraindividual variability, might lead to overestimation of rCBF in patients with severe intracranial insult. The obtained How activati on curve provides essential information that may allow subsequent refinemen t of the methodology, aiming to further minimize the influence of Xe-s-indu ced rCBF activation on rCBF calculations when using Xe-s/CT technology.