Dual-phase CT angiography of the normal canine portal and hepatic vasculature.

A dual-phase computed tomography (CT) angiographic technique was developed to image the hepatic and portal vascular systems using a nonselective peripheral injection of contrast medium. The arterial phase of the dual-phase scan imaged the hepatic arteries and veins, and the portal phase imaged the portal vein as well as its tributaries and branches. There were three steps involved in acquiring the dual-phase scan: a survey helical scan for orientation, a dynamic scan for timing, and finally the dual-phase helical scan. Five normal dogs were imaged using a helical scan technique. The timing of the arterial and portal phases of the scan was calculated using time vs. attenuation graphs generated from a dynamic scan. The median time of appearance of contrast medium in the cranial abdominal aorta was 8.6 s and the median time of appearance of contrast medium in the hepatic artery occurred 0.4 s later. The median time of peak enhancement in the cranial abdominal aorta was 12.0 s. The median time of appearance of contrast medium in the portal vein was 14.6 s and median time of peak enhancement was 33.0 s. The dual-phase scans provided excellent vascular opacification. The hepatic arteries, hepatic veins, cranial and caudal mesenteric veins, splenic vein, gastroduodenal vein, and portal vein branches were all consistently well defined. Dual-phase CT angiography is a minimally invasive technique which provides an excellent three-dimensional representation of portal and hepatic vascular anatomy.