Effect of xenon-induced flow activation on xenon-enhanced computed tomography cerebral blood flow calculations.

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.