Evaluation of hepatic perfusion disorders with double-phase spiral CT.

Double-phase (dual-phase) spiral computed tomography (CT) represents a technologic advance that allows two evaluations of hepatic blood flow during a single 19-29-second breath hold: once during the hepatic arterial phase (HAP) and again during the portal venous phase (PVP). Perfusion disorders of the hepatic parenchyma are more readily observed at double-phase spiral CT. The various hepatic perfusion disorders are related to (a) portal venous inflow obstruction, (b) hepatic venous outflow obstruction (e.g., Budd-Chiari syndrome, cardiac failure, mediastinal fibrosis), (c) mediastinal or thoracic venous inlet obstruction, (d) focal liver lesions, (e) inflammatory processes, (f) normal anatomic variants in the hepatic blood supply, (g) altered hemodynamics after the placement of a transjugular intrahepatic portosystemic shunt, and (h) uncertain causes. In general, the area of involvement appears hyperattenuating on HAP images and of normal or near-normal attenuation on PVP images. Familiarity with the spiral CT appearances of different types of perfusion disorders allows the radiologist to separate clinically insignificant flow phenomena from perfusion disorders caused by underlying parenchymal or vascular disease.