CT scanning protocol in washin/washout method to reduce the effect of xenoninduced flow activation on xenon-enhanced computed tomography calculations: cerebral blood flow and partition coefficient

Abstract

Background: It has been required to reduce the effect of xenon-induced flow activation (Xe activation) in xenonenhanced computed tomography (Xe-CT). The goal of this work was to propose a CT scanning protocol in the washin/washout method that could reduce the Xe-activation effect on calculated cerebral blood flow (CBF) and partition coefficient (lambda) in Xe-CT. Methods: In the 4-min washin/4-min washout protocol with 1-min interval scans, the effect of Xe activation was calculated by theoretical simulations under the following scanning protocols based on the reported transcranial Doppler measurements: A: 1-min intervals, B: skip scans during the first 2 min in washout, and C: no scan in washout. For ten healthy subjects, CBF and lambda for the cortical regions of the right and left middle cerebral artery (MCA) territories were evaluated in protocols A and B. Results: Due to Xe activation, simulated CBF for gray matter was changed by 13%, 7% and 6%; simulated lambda for gray matter was changed by 2%, 4% and 4%; simulated CBF for white matter was changed by 11%, 10% and -1%; and simulated lambda for white matter was changed by 14%, 14% and 133% in protocols A, B and C, respectively. For the ten subjects, the mean differences between protocols A and B in obtained CBF were 1.85 (P=0.0337) and 2.23 mL/100g/min (P=0.0077), and those in obtained lambda were -0.042 (P<0.0001) and -0.041 (P<0.0001) for the right and left MCA territories respectively. This demonstrated that gray matter CBF by protocol A was statistically larger than that by protocol B, and gray matter lambda by protocol A was statistically smaller than that by protocol B, which agreed with the theoretical simulation results.