CT DURING ARTERIAL PORTOGRAPHY

CT during arterial portography (CTAP) is based on portal enhancement o f the liver by infusion of contrast material through the superior mese nteric or splenic artery. This technique provides high degrees of enha ncement of the portal vein and intrahepatic vessels, allowing reliable segmental localisation of tumours and accurate assessment of relation ships between tumours and intrahepatic vessels. Because of its invasiv eness, CTAP must be limited to patients for whom non-invasive preopera tive imaging suggests resectable tumour. In the majority of cases, CTA P is performed in patients with hepatic metastases from colorectal can cer, but other types of hepatic tumour (either primary or secondary) a nd pancreatic tumour may be an indication for CTAP. Visualisation of n on-tumorous perfusion defects is a limitation of this technique, but s uch defects have been well described and have characteristic locations and appearance. In difficult cases, correlation with sonographic, CT and MRI findings helps characterise portal perfusion defects. CTAP is the most sensitive technique for the detection of intrahepatic tumours , and the recent use of spiral technology shows promise in the perform ance of CTAP. CTAP data can be viewed as multiplanar and three-dimensi onal reconstructions that allow preoperative planning of the extent of resection and determination of the volume of the remaining liver afte r resection.