LI-RADS major features: CT, MRI with extracellular agents, and MRI with hepatobiliary agents

Abstract

The Liver Imaging Reporting and Data System (LI-RADS) was designed to standardize the interpretation and reporting of observations seen on studies performed in patients at risk for development of hepatocellular carcinoma (HCC). The LI-RADS algorithm guides radiologists through the process of categorizing observations on a spectrum from definitely benign to definitely HCC. Major features are the imaging features used to categorize observations as LI-RADS 3 (intermediate probability of malignancy), LIRADS 4 (probably HCC), and LI-RADS 5 (definite HCC). Major features include arterial phase hyperenhancement, washout appearance, enhancing capsule appearance, size, and threshold growth. Observations that have few major criteria are assigned lower categories than those that have several, with the goal of preserving high specificity for the LR-5 category of Definite HCC. The goal of this paper is to discuss LI-RADS major features, including definitions, rationale for selection as major features, and imaging examples.

Liver Imaging Reporting and Data System Version 2018: Impact on Categorization and Hepatocellular Carcinoma Staging

“…). Except for threshold growth, the definition of which was simplified in v2018, MFs have been stable over multiple versions of LI‐RADS and were most recently published in the American College of Radiology CT/MRI LI‐RADS v2017 core . During the study period, the examinations were interpreted by faculty radiologists (n = 16 during the study period), all with fellowship training and expertise in abdominal imaging and in the application of LI‐RADS, each with 1 or more years of postfellowship experience in CT and MRI of the liver.…”

LI‐RADS 2017: An update

“…APHE is defined by the presence of enhancement that is unequivocally greater than that of the background liver. 12,13 In v2017, the distinction is made between rim and nonrim APHE, depending on whether or not enhancement is primarily confined to the periphery of the observation. 13 For LR-5 categorization, nonrim APHE must be present.…”

“…13 “Washout” is assessed in the PVP or DP with the use of the gadolinium-based extracellular contrast agents (ECA) or gadobenate, and in the PVP only if gadoxetate disodium is used. 13 The restriction applied to the gadoxetate-enhanced MRIs is based on the fact that apparent hypointensity of an observation in the 3–5 minutes transitional phase (TP) may be due to relative hyperenhancement of the parenchyma rather than a true tumor washout. As the result, specificity of an HCC diagnosis may decrease slightly if transitional phase hypointen-sity were to be accepted as “washout.” 14,15 With regard to the assessment of “washout,” Liu et al confirmed that detection of this imaging feature depends on many factors, which can include a radiologist’s subjective visual assessment and level of experience, in addition to window and level settings.…”

“…21 The presence of any of the LR-M features is sufficient for LR-M categorization. In order to distinguish the LR-M features from the major features, v2017 added qualifiers “nonrim” and “nonperipheral” for APHE and “washout,” respectively 13 (Fig. 4).…”

“…38 The LI-RADS algorithm is equally applicable to MRI both with ECA and gadoxetate, with the exception of the aforementioned “washout” assessment, which is restricted to the PVP with gadoxetate as opposed to the PVP and DP with ECA and gadobenate. 11,13 …”