HEPATOCELLULAR-CARCINOMA IN NORTH-AMERICA - A MULTIINSTITUTIONAL STUDY OF APPEARANCE ON T1-WEIGHTED, T2-WEIGHTED, AND SERIAL GADOLINIUM-ENHANCED GRADIENT-ECHO IMAGES

OBJECTIVE. The purpose of this study was to define the common appearan ces of hepatocellular carcinoma (HCC) in patients in North America by analyzing T1-weighted, T2-weighted, and serial gadolinium-enhanced gra dient-echo images interpreted by radiologists at multiple institutions in North America. MATERIALS AND METHODS. One hundred thirteen consecu tive patients with HCC from eight institutions were included in this r etrospective case series. Inclusion criteria included MR imaging exami nations performed on 1.5-T MR imagers using T1-weighted breath-hold sp oiled gradient-echo images, T2-weighted images, and serial gadolinium- enhanced spoiled gradient-echo images. Diagnosis was established by hi stology in all patients. Images were analyzed retrospectively for lesi on count, lesion diameter as less than or equal to 1.5 cm and greater than 1.5 cm, and signal intensity, by individual experienced radiologi sts at each institution. RESULTS. We found 354 HCC lesions in the 113 patients. Tumors were solitary in 63 patients, multifocal in 45 patien ts, and diffuse in five patients. Lesion appearance on combined T1-wei ghted, T2-weighted, and immediate gadolinium-enhanced spoiled gradient -echo images was as follows: 102 lesions (29%) were hypointense on T1- weighted images, were hyperintense on T2-weighted images, and exhibite d diffuse heterogeneous enhancement; 52 lesions (15%) were isointense on both T1- and T2 weighted images and exhibited diffuse homogeneous e nhancement (all of these lesions measured less than or equal to 1.5 cm in diameter); 50 lesions (14%) were hypointense on T1-weighted images , were hyperintense on T2-weighted images, and exhibited diffuse homog eneous enhancement; 33 lesions (9%) were hypointense on T1-weighted im ages, were hyperintense on T2-weighted images, and exhibited predomina ntly peripheral rim enhancement; and 27 lesions (8%) were hypointense on T1-weighted images, were isointense on T2-weighted images, and exhi bited diffuse homogeneous enhancement. The remaining 90 lesions showed less common patterns. The appearance of HCCs greater than 1.5 cm and of HCCs less than or equal to 1.5 cm was significantly different (p = .001). The appearance of histologically proven HCCs is separately desc ribed. CONCLUSION, The combination of hypointensity on T1-weighted ima ges, hyperintensity on T2-weighted images, and diffuse heterogeneous e nhancement was the most common appearance of HCC on MR images in a mul tiinstitutional patient population in North America. Small HCCs measur ing less than or equal to 1.5 cm were frequently isointense on both T1 -weighted and T2-weighted images and may be detected on immediate gado linium-enhanced images only as diffuse homogeneously enhancing lesions .