CHARACTERIZATION OF FOCAL HEPATIC-TUMORS - VALUE OF 2-PHASE SCANNING WITH SPIRAL COMPUTED-TOMOGRAPHY

Background. Spiral computed tomography (CT) allows imaging of the live r during the peak contrast material levels due to the capability of fa st data acquisition. The objective of this study was to evaluate the u sefulness of two-phase spiral CT in the differential diagnosis of foca l hepatic tumors. Methods. One hundred two patients who had hepatic tu mors (211 nodules; 149 hepatocellular carcinomas [HCCs], 36 metastases , and 26 hemangiomas) underwent two-phase spiral CT with 10-mm collima tion at 10 mm/ second table speed and 120 mi of contrast material inje cted at the rate of 3 mL/second. Computed tomography images of the hep atic arterial phase and late (equilibrium) phase were obtained at 35-s econd and 180-second delays, respectively. The enhancement patterns of tumors were divided into six types and were compared with the attenua tion of surrounding liver parenchyma: totally high, peripherally high, centrally high, mixed, iso, and low. Results. The common enhancement patterns of HCC in two-phase spiral CT were totally high in the arteri al phase and low (n = 63, 42%) or iso (n = 28, 19%) in the late phase. Metastasis showed peripherally nonnodular high attenuation (n = 9, 25 %) or low attenuation (n = 9, 25%) in the arterial phase and low atten uation in the late phase, followed by totally high attenuation in the arterial phase and iso in the late phase (n = 6, 17%). Hemangiomas sho wed totally or peripherally nodular enhancement in the arterial and la te phases (n = 23, 89%). In distinguishing hemangiomas from malignant tumors, totally high or peripherally nodular high attenuation in the l ate phase was the most useful contrast enhancement pattern (96% of hem angioma vs. 0% of malignant tumors). In distinguishing HCCs from metas tases, a combination of contrast enhancement pattern of totally high a ttenuation in the arterial phase and low in the late phase was the mos t useful contrast enhancement pattern (42% of HCCs vs. 0% of metastase s). The predictability of differentiation between hemangiomas and mali gnant tumors and between HCCs and metastases was 99% and 90% with spir al CT, respectively. Conclusions. Two-phase spiral CT is useful in the differential diagnosis of focal hepatic tumors with evaluation of con trast enhancement patterns.