A 57-year-old man with a history of Duke’s C colon cancer is being evaluated for a rising CEA. Which of the following statement(s) is/are correct concerning the use of CT scanning for this indication?

b.CT arterio-portography involves immediate CT scanning after direct injection into both the common hepatic artery and superior mesenteric artery

c.A double helical (spiral) CT scan may eliminate the need for invasive angiography

d.Magnetic resonance imaging of the liver will add little to the workup of this patient

CT scanning has been used increasingly to screen for hepatic and other intra-abdominal or retroperitoneal lesions. Conventional CT scanning includes 0.5–1 cm axial images of the liver after oral administration of barium and bolus injection of intravenous contrast. Although resolution has improved, hepatic lesions below 1 cm in size or lesions that are isodense with hepatic parenchyma may be missed. Resolution of hepatic lesions has been greatly enhanced by the combination of visceral angiography and CT scanning, known as CT arterio-portography (CTAP). Immediate CT scanning after injection of contrast directly into the common hepatic artery may identify small hepatic lesions which usually show increased density relative to the surrounding hepatic parenchyma. CT arterio-portography also includes direct injection of contrast into the splenic or superior mesenteric arteries, with CT imaging during the portal venous phase of this injection. Hepatic lesions supplied by the hepatic artery thus appear as discrete hypodense lesions surrounded by normal hepatic parenchyma enhanced by portal venous contrast. Recently, double helical (spiral) CT scanning has become available and shows considerable promise to complement or replace CTAP for preoperative imaging. This technique allows total hepatic imaging in both the arterial and arterial/venous phases after a single rapid bolus injection of intravenous contrast during a single breath hold by the patient. It is possible to visualize the portal structures and hepatic veins on a single scan and give a high resolution of small hepatic lesions. In addition, threedimensional reconstructions can be created to further delineate hepatic parenchyma and demonstrate a CT constructed hepatic arteriogram. This technique may completely replace the need for invasive arteriography to characterize the blood supply to the liver prior to hepatic resection or after hepatic transplantation. Magnetic resonance imaging of the liver has results similar to CT scanning, but to date has not demonstrated improvements sufficient to justify the increased cost associated with the technique.