Evaluation of hepatic blood flow using maximum entropy methods

Using spectrum analysis (Maximum entropy methods; MEM), we separated the portal venous and the hepatic arterial components from the time activity curve (TAC) obtained by RI angiography of sup(99m)Tc-phytate. We set the region of interest on the right lobe of the liver and the left kidney, and set the short and the long section to the differentiated TAC of the liver and the TAC of the kidney. Sectioning was done as follows: 1) short section, from the point at 20 % of the peak to the point at the peak of the kidney. 2) long section, from the point at 20 % of the peak to the point at 0 which was extrapolated from the initial slope of the TAC of the kidney. We analysed these sections using MEM. The fast cycle (FC) obtained from the short section was related to the mean transit time (MTT) of the hepatic artery. The slow cycle (SC) obtained from the long section was related to the MTT of the portal vein. FC and SC were calculated on the liver and the kidney. Clinically, we compared the normal liver with liver chirrhosis. In normal, the liver to kidney ratio of FC and SC were 0.90 +- 0.14 and 1.08 +- 0.11, respectively. In cirrhosis, the liver to kidney ratio of FC and SC were 0.66 +- 0.16 and 1.65 +- 0.35, respectively. These results were reasonable for the hemodynamics of the diseased liver. (author)