Multiphase hepatic CT with a multirow detector CT scanner

OBJECTIVE. The aim of this study was to evaluate a new injection-acquisitio n technique performed using a multirow detector CT scanner for separation o f three distinct hepatic circulatory phases (hepatic artery, portal venous inflow, hepatic venous) and to determine which of these phases is optimal f or detecting hypervascular neoplasm. MATERIALS AND METHODS. Two sequential acquisitions were performed during a single breath-hold followed by a third acquisition beginning 60 sec after i njection. Injection-to-scan delay for the first acquisition was the individ ual patient's circulation time, which was determined by a preliminary mini bolus. The mean attenuation of the upper abdominal aorta, portal vein, and hepatic parenchyma were determined for each imaging pass in 20 patients wit h cirrhosis and 20 patients without cirrhosis. Tumor-to-liver contrast for hypervascular primary and metastatic neoplasm was evaluated in a different set of 16 cirrhotic patients and nine noncirrhotic patients. Three-dimensio nal CT arteriograms were obtained from first-pass data. RESULTS. Three distinct circulatory phases (hepatic artery, portal vein inf low or late arterial, and hepatic venous) were seen in cirrhotic and noncir rhotic patients. Maximum tumor-to-liver contrast for hypervascular primary and metastatic neoplasm occurred during the second pass for both cirrhotic (p < 0.005) and noncirrhotic (p < 0.001) patients. A three-dimensional hepa tic-mesenteric CT arteriogram of normal or anomalous hepatic vessels withou t venous overlay was obtained from first-pass data in all patients. CONCLUSION. Rapid-sequence hepatic helical CT allows selection of the optim al time interval fur hypervascular tumor detection. A new paradigm for rapi d hepatic CT acquisition-namely, hepatic arterial, portal vein inflow, and hepatic venous phases-is recommended to replace hepatic artery dominant and portal venous phases.