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Page 2 of 11 Kanmaniraja et al. Hepatoma Res 2020;6:51 I http://dx.doi.org/10.20517/2394-5079.2020.46
[5]
confirmation . When biopsy is required, it is often done with image guidance; furthermore, imaging
[6]
plays an integral role in patients undergoing surveillance or following loco-regional therapy . The Liver
Imaging Reporting and Data System(LI-RADS) is a comprehensive and dynamic system which provides
a standardized means of assessing and communicating the entire spectrum of lesions and pseudolesions
[7,8]
in studies performed in patients who are at risk for developing HCC . LI-RADS is developed by an
international multidisciplinary consortium of radiologists, hepatologists, hepatobiliary surgeons, and
[7,8]
hepatopathologists .
OVERVIEW
Multiple societies and organizations have proposed image-based systems for the diagnosis of HCC. In
2008, the American College of Radiology proposed the LI-RADS with the primary goal of standardizing
the lexicon, interpretation, and reporting of imaging studies specifically in patients who are at risk for
developing HCC. The aim was to establish a comprehensive algorithm that would accurately stratify the
probability of HCC and malignancy in each observation, while still maintaining a high specificity for
HCC . The first version was released in 2011, followed by major updates in 2013, 2014, 2017, and 2018.
[7]
With the most recent changes in 2018, LI-RADS was integrated into the American Association for the
[6]
Study of Liver Disease (AASLD) practice guidance for HCC .

Currently, LI-RADS has four individual algorithms that are used in different clinical contexts. Ultrasound
LI-RADS is used for surveillance of at-risk patients. Contrast-enhanced ultrasound LI-RADS is used for
the diagnosis of HCC. Computed tomography/magnetic resonance imaging (CT/MRI) LI-RADS algorithm
is used for diagnosis and staging of HCC. Treatment response LI-RADS algorithm is used following local-
regional therapy. This manuscript focuses on LI-RADS CT/MRI diagnostic algorithm.

CT/MRI DIAGNOSTIC ALGORITHM
LI-RADS CT/MRI Diagnostic Algorithm version 2018 (v2018) includes eight diagnostic categories which
are applied to individual observations with increasing probability of HCC and malignancy with higher
categories. The various categories do not have an exact correlation to the histologic categories but instead
reflect the probability of individual observations being benign, HCC, or non-HCC malignancy. For
instance, although all observations in LR-1 are benign and all observations in LR-5 are HCC, the opposite
is not true, as many benign lesions may not be categorized LR-1 and not all HCC meet criteria for the LR-5
[9]
category .
A multiphase contrast-enhanced study is required for appropriate assessment of liver observations.
Multiphase studies include late arterial phase, portal venous phase, and delayed phase. Extracellular
contrast agents are used for CT exams, while either an extracellular or hepatobiliary agent may be used
[7]
for MRI . Extracellular MRI contrast agents provide lesion characteristics based primarily on blood flow,
[6]
while hepatobiliary agents utilize information from both blood flow and the hepatocellular function .
Although recent meta-analyses studies have shown multiphase contrast-enhanced MRI to have a higher
sensitivity than CT for the diagnosis of HCC with similar specificity, there is currently insufficient evidence
to recommend one modality or contrast agent over the other [6,7,10] . Practitioners and institutions are
encouraged to make decisions based on their best judgement, as well as to develop their own approach
based on a multidisciplinary consensus that would be best suited both for the individual patient and the
institution as a whole . In treatment-naïve patients, the unenhanced phase on CT is optional, while it
[6]
[7]
is required in patients following loco-regional therapy . Late arterial phase (AP) imaging is strongly
preferred over the early AP to improve detection of the arterial phase hyperenhancement, an imaging
[7]
feature that is required for imaging diagnosis of HCC .