The Role of Diffusion Weighted MR Imaging in Assessment of Hepatocellular Carcinoma after RadiofrequencyAblation

Abstract

MRI is a sensitive modality in detection and characterization of hepatic focal lesion. MRI has traditionally been used to evaluate treatment response in malignant liver lesions; however, the assessment of tumor response after certain treatments, such as RFA can be difficult. In our study, patients were assessed with conventional MRI, post contrast dynamic MRI and DWI on 1.5 Tesla MRI system. Post treatment moderate hyper intensity of the lesion on T2-weighted images suggests residual/recurrent lesions while marked hyper intensity which appears on heavy T2-weighted images should suggest liquifactive necrosis. Arterial phase enhancement (especially late arterial phase) with washout of the contrast in the venous & delayed phases and delayed capsular enhancement are diagnostic for residual/recurrent lesions on follow up post intervention. In follow up of the hepatic focal lesion after intervention, the necrotic tissue shows no contrast enhancement in the arterial phase which should be supported by subtraction images to remove the intrinsic hyperintense signal of the coagulative necrosis and hemorrhagic products.