Effect of Xenon-Induced Flow Activation on Xenon-Enhanced Computed Tomography Cerebral Blood Flow Calculations

Abstract

Computer simulations of stable xenon ((S)Xe) uptake curves were used to evaluate the effect of xenon-induced flow activation on CBF calculations by xenon-enhanced computed tomography. Estimates of flow activation were based on repeated transcranial Doppler measurements of blood velocity during 4.5 minutes of (S)Xe inhalation. The synthetic curves were generated from a generalized Kety equation that included time-varying blood flow activation. In contrast to the peak 35% increase in blood flow velocity during (S)Xe inhalation, a standard analysis of the flow-varying synthetic curves revealed only minor 3% to 5% increases in calculated CBF. It is concluded that brief xenon inhalations can provide blood flow estimates that contain minimal bias from activation.

Comparative Overview of Brain Perfusion Imaging Techniques

“…This reliability, despite the pharmacological property of Xenon to directly increase CBF by 20% to 30%, is explained by the fact that nearly all the important flow data are acquired before this flow activation (the latter becomes significant only after 2.5 minutes of inhalation). 48 Reliability is also increased by use of a flow phantom that permits standardization of the data and the calibration of scanners from different manufacturers.…”

Guidelines and Recommendations for Perfusion Imaging in Cerebral Ischemia

“…115 This reliability in spite of the pharmacological property of xenon to directly increase CBF by 20% to 30% is explained by the fact that nearly all of the important flow data are acquired prior to this flow activation, which does not become significant until after 2.5 minutes of inhalation. 116 The use of a flow phantom not only allows each scanner to be calibrated between studies, but its universal use by all sites performing XeCT examinations permits standardization of the data between scanners of different manufacturers and the potential integration and comparison of the data for multi-institutional studies.…”

Cerebrovascular Reserve in Patients With Carotid Occlusive Disease Assessed by Stable Xenon-Enhanced CT Cerebral Blood Flow and Transcranial Doppler

“…Modeling has provided further support by confirming a minimal effect of Xe inhalation on the calculated versus "real" CBF values using the currently employed method for calculated CBF. 31 Xe also has an effect on the sensorium, but with the reduction in Xe from 33% to 28%, there has been a significant reduction in even minimal symptoms.…”