Major and ancillary magnetic resonance features of LI-RADS to assess HCC: an overview and update

Abstract

Liver Imaging Reporting and Data System (LI-RADS) is a system for interpreting and reporting of imaging features on multidetector computed tomography (MDCT) and magnetic resonance (MR) studies in patients at risk for hepatocellular carcinoma (HCC). American College of Radiology (ACR) sustained the spread of LI-RADS to homogenizing the interpreting and reporting data of HCC patients. Diagnosis of HCC is due to the presence of major imaging features. Major features are imaging data used to categorize LI-RADS-3, LI-RADS-4, and LI-RADS-5 and include arterial-phase hyperenhancement, tumor diameter, washout appearance, capsule appearance and threshold growth. Ancillary are features that can be used to modify the LI-RADS classification. Ancillary features supporting malignancy (diffusion restriction, moderate T2 hyperintensity, T1 hypointensity on hapatospecifc phase) can be used to upgrade category by one or more categories, but not beyond LI-RADS-4. Our purpose is reporting an overview and update of major and ancillary MR imaging features in assessment of HCC.

Joint Consensus Statement of the Indian National Association for Study of the Liver and Indian Radiological and Imaging Association for the Diagnosis and Imaging of Hepatocellular Carcinoma Incorporating Liver Imaging Reporting and Data System

“…As such, DWI may be useful in detecting HCC among benign nodules and arterially enhancing pseudo-lesions, assessing response to treatment, because treatment-induced necrotic and inflammatory tissue result in a loss of cellular density and an increase in membrane permeability with subsequent diminished restriction of diffusion. [89][90][91] All reports seemed to agree that DWI, as a diagnostic criterion for HCC, improved the sensitivity of conventional MRI, and the greatest benefit lied in the combined use of both (pooled sensitivity and specificity: 93% and 84% combined, respectively). However, cirrhotic parenchyma may itself show restricted diffusion, presumably owing to the abundance of fibrotic tissue, which results in reduced HCC conspicuity in DWI.…”

“…The addition of T2-WI hyperintensity to the AASLD criteria improved the detection rate of HCC, especially in nodules <20 mm, by increasing sensitivity from 67.6% to 79%. [88][89][90][91] Sofue et al evaluated the imaging features in MRI associated with the upgrade to a LI-RADS 5 category and verified that the risk factors in the 56 LR-4 observations, which were upgraded to LR-5, included mild to moderate T2 hyperintensity (P < 0.001) and growth (P < 0.001) 92 . Hyperintensity on T2-WI and DWI could also be useful in differentiating hypovascular HCCs from dysplastic nodules, which are perceived as hypointense nodules in the HPB phase.…”

“…This feature can be useful for the differentiation between a dysplastic nodule and a small HCC, especially when the latter presents as a hypervascular nodule without washout. [88][89][90][91] HCCs tend to show minimal to mildly increased signal intensity on T2-WI, with specificity and a positive predictive value ranging between 73%-100% and 72%-100%, respectively. The addition of T2-WI hyperintensity to the AASLD criteria improved the detection rate of HCC, especially in nodules <20 mm, by increasing sensitivity from 67.6% to 79%.…”

“…Liver iron deposition can be shown as signal loss on the second echo of a dual-echo sequence or as abnormal hypointensity on T2 or T2*-weighted images, however not specific to HCC, as it may also be observed in other malignancies, such as ICC, and nonmalignant processes such as confluent fibrosis. Intralesional fat than background liver tissue [88][89][90][91] reflects fatty metaplasia frequently histologically observed in early HCCssensitivity, specificity ranging from 12% to 37%/68%-91%, respectively. High-grade and occasionally low-grade dysplastic nodules may also show intralesional fat.…”

CT-MRI LI-RADS v2017: A Comprehensive Guide for Beginners

“… 16 Nevertheless, these guidelines have some limitations, such as the inconsistency between different systems in definition of pathological features, the extent of the indeterminate category and the lack of indications for differential diagnosis from other malignancies or for characterization of macrovascular invasion. 17 , 18 Proposed for the first time in 2011 and then updated in 2013, 2014 and 2017, the Liver Imaging-Reporting and Data System (LI-RADS) is a comprehensive system for standardized interpretation and reporting of CT and MR liver examinations, endorsed by the American College of Radiology to overcome the mentioned limits and achieve congruence with HCC diagnostic criteria in at-risk populations. 17 , 18 …”