Quantitative Tissue Blood Flow Measurement of the Liver Parenchyma: Comparison Between Xenon CT and Perfusion CT

The purpose of this study was to compare measurements of hepatic tissue blood flow (TBF) calculated by xenon and perfusion CT. Seven patients with normal liver and eight with chronic liver disease underwent both xenon and perfusion CT. During xenon CT examinations, serial abdominal CT scans were obtained every minute before and during 4 min of nonradioactive 25% (v/v) xenon gas inhalation and 5 min of administration of oxygen-rich air. Hepatic arterial and portal venous TBF were measured separately with a special imaging system using the Kety-Schmidt expression based on the Fick principle (AZ-7000W; Anzai Medical Co.). The hepatic arterial fraction (HAF) was calculated as follows: [hepatic arterial TBF/(hepatic arterial TBF + portal venous TBF)]. During perfusion CT examinations, total hepatic TBF and HAF were also calculated from the enhanced CT cine image data on a workstation using a commercially available software package based on a deconvolution algorithm (CT Perfusion 3 GE Healthcare, USA). Total hepatic TBF measured by xenon and perfusion CT was 82.9±15 and 82.8±18 ml/min/100 g, respectively. The measured values by the two techniques showed a significant correlation (R2= 0.657, P < 0.05). HAF measured by xenon and perfusion CT was 26.6±11 and 21.8±13%, respectively. The measured values by the two techniques also showed a significant correlation (R2= 0.869, P < 0.05). We conclude that there was a good correlation between hepatic TBF quantified by xenon CT and perfusion CT.