Quantitative computed tomography of the brain with xenon enhancement: a phantom study with the GE9800 scanner

A recently proposed application of quantitative computed tomography is in the study of cerebral blood flow and partition coefficient using stable xenon as a freely diffusible, radio-opaque tracer. Central to the method is the calibration factor describing the relationship between CT number and xenon concentration in the brain. In this paper we examine the influence of temporal fluctuations, kVp, radial position and beam hardening on this calibration factor through the analysis of a series of phantom measurements. We conclude that under clinically realistic conditions and with correlations for temporal fluctuations, the error associated with the calibration factor is less than 2%. Furthermore, errors of this magnitude translate into errors of less than 3% in derived blood flow and partition coefficient values obtained using xenon-enhanced computed tomography.