Dynamic CT for Detecting Small Hepatocellular Carcinoma: Usefulness of Delayed Phase Imaging

OBJECTIVE. The purpose of this retrospective study was to determine the usefulness of delayed phase imaging for detecting small (≤ 2 cm) hepatocellular carcinomas (HCCs) in patients with liver cirrhosis.MATERIALS AND METHODS. Triphasic (arterial, portal venous, and delayed phases) dynamic CT was performed in 33 patients with 48 HCCs proven histopathologically and in 65 control subjects. Arterial, portal venous, and delayed phase images were obtained 30 seconds, 68-70 seconds, and 5 minutes after the start of contrast material injection, respectively. Three blinded observers reviewed the images independently and evaluated tumor attenuation. Diagnostic performance for the combination of phases was assessed using receiver operating characteristic (ROC) curve analysis.RESULTS. On arterial phase images, 28 of the 48 HCCs were hyperattenuating, nine were isoattenuating, and 11 were hypoattenuating. On portal venous phase images, three tumors were hyperattenuating, 17 were isoattenuating, and 28 were hypoattenua...