MR Imaging of Hepatocellular Carcinoma in the Cirrhotic Liver: Challenges and Controversies

Abstract

The incidence of hepatocellular carcinoma (HCC) is expected to increase in the next 2 decades, largely due to hepatitis C infection and secondary cirrhosis. HCC is being detected at an earlier stage owing to the implementation of screening programs. Biopsy is no longer required prior to treatment, and diagnosis of HCC is heavily dependent on imaging characteristics. The most recent recommendations by the American Association for the Study of Liver Diseases (AASLD) state that a diagnosis of HCC can be made if a mass larger than 2 cm shows typical features of HCC (hypervascularity in the arterial phase and washout in the venous phase) at contrast material-enhanced computed tomography or magnetic resonance (MR) imaging or if a mass measuring 1-2 cm shows these features at both modalities. There is an ever-increasing demand on radiologists to detect smaller tumors, when curative therapies are most effective. However, the major difficulty in imaging cirrhosis is the characterization of hypervascular nodules smaller than 2 cm, which often have nonspecific imaging characteristics. The authors present a review of the MR imaging and pathologic features of regenerative nodules and dysplastic nodules and focus on HCC in the cirrhotic liver, with particular reference to small tumors and lesions that may mimic HCC. The authors also review the sensitivity of MR imaging for the detection of these tumors and discuss the staging of HCC and the treatment options in the context of the guidelines of the AASLD and the imaging criteria required by the United Network for Organ Sharing for transplantation. MR findings following ablation and chemoembolization are also reviewed.

Gadoxetic acid‐enhanced MRI versus multiphase multidetector row computed tomography for evaluating the viable tumor of hepatocellular carcinomas treated with image‐guided tumor therapy

“…Hemodynamic alteration, such as microscopic arterioportal shunting around the treated HCC after RFA or TACE, or hypervascular enhancement around RFA representing inflammatory reactions to thermal injury, can occur (22,27). As described in several previous reports (2,3), we believe that this hemodynamic alteration owing to imageguided tumor therapy can resemble or mask HCCs.…”

“…In our study, two observers achieved significantly higher Az values, diagnostic accuracies, sensitivities and negative predictive values when using gadoxetic acid-enhanced 3.0T MRI as compared to MDCT. The previously reported sensitivity of CT and MRI for the detection of small foci of residual or recurrent tumors after RFA ranged from 36-89% in the published literature (22). Several investigators have reported a sensitivity of 45-49% for the detection of HCC recurrence after TACE with CT scans combined with serum a-fetoprotein level (18,23).…”

Asian Pacific Association for the Study of the Liver consensus recommendations on hepatocellular carcinoma

“…The operative characteristics of CT are comparable, whereas MRI is more sensitive. The performance of CT and MRI is affected by the size of the lesions [204,205]. Although CT and MRI are reported to have a sensitivity of 60-94.4% and 58.5-93%, respectively, in tumors larger than 1 cm, their sensitivities for detecting tumors smaller than 1 cm are reduced by 33-45 and 33-67%, respectively [204,[206][207][208].…”

“…If left alone, these tumors can grow aggressively and invasion can occur before tumors reach the 2-cm cutoff size for small HCC [202]. Thus, every attempt, including imaging follow-up or biopsy, should be made to characterize these nodules [205].…”

“…Hypovascular nodules associated with liver cirrhosis include low-or high-grade dysplastic nodules (HGDN), early HCCs, and well-differentiated HCCs [201,[220][221][222].There are significant overlaps in enhancement patterns on dynamic CT or dynamic MRI and in signal intensity on T2-weighted images [200,201,205]. Indeed, the noninvasive diagnostic criteria based on arterial hypervascularization in contrast-enhanced imaging techniques, published by the European Association for the study of the liver (EASL), are satisfied in only 61% of small nodules in cirrhosis [223].…”