Resovist enhanced MR imaging of the liver: does quantitative assessment help in focal lesion classification and characterization?

Purpose: To improve characterization of focal liver lesions by a prospective quantitative analysis of percentage signal intensity change, in dynamic and late phases after slow (0.5 mL/s) Resovist administration. Materials and Methods: Seventy-three patients were submitted on clinical indication to MR examination with Resovist. Signal intensity of 92 detected focal lesions (5–80 mm) were measured with regions of interest and normalized to paravertebral muscle in arterial, portal, equilibrium and T1/T2 late phases, by two observers in conference. Five values of percentage variations per patient were obtained and statistically evaluated. Results: The enhancement obtained on dynamic study is more suitable in hemangiomas and focal nodular hyperplasias than in adenomas and hepatocellular carcinomas. To discriminate benign versus malignant lesions on latephase- T2-weighted images, a cutoff ¼ 26%, allowed sensitivity and specificity values of 97.4% and 97.7%, respectively. Area under the receiver operating characteristic (ROC) curve was 0.99. To differentiate hemangioma versus all other focal liver lesions, on late-phase-T1- weighted images, a cutoff ¼ þ40% permitted sensitivity and specificity values of 90.5% and 98.0%, respectively. Area under the ROC curve was 0.98. Conclusion: Late phase quantitative evaluation after slow Resovist administration, allows to differentiate malignant from benign hepatic masses and hemangiomas from all the others focal liver