Focal liver lesions: Pattern-based classification scheme for enhancement at arterial phase CT

PURPOSE: To present our early experience with a classification scheme for c ategorizing focal liver lesions on the basis of the enhancement patterns th at they exhibit in the arterial phase of computed tomography (CT) and to de termine whether particular enhancement patterns suggest particular diagnose s. MATERIALS AND METHODS: The authors reviewed arterial phase CT images in 100 consecutive patients with focal liver lesions, excluding simple cysts. The enhancement pattern of the dominant or representative lesion in each patie nt was classified into one of five categories-homogeneous, abnormal interna l vessels or variegated, peripheral puddles, complete ring, or incomplete r ing-by three radiologists blinded to the proved diagnosis. Lesions without enhancement were recorded separately. Agreement was reached by consensus in all cases. Standards of reference included findings at histologic examinat ion, correlative imaging, or clinical and imaging follow-up. RESULTS: Ninety-two percent of the 100 lesions demonstrated arterial phase enhancement. Patterns associated with positive predictive values of 82% or greater and specificity of 80% or greater included abnormal internal vessel s or variegated (hepatocellular carcinoma), peripheral puddles (hemangioma) , and complete ring (metastasis). CONCLUSION: The appearance of hepatic lesions in the arterial phase of enha ncement has potential use in the determination of specific diagnoses. The c lassification scheme used in this study may be a useful tool for the interp retation of arterial phase CT studies.