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Page 8 of 14 Santillan Hepatoma Res 2020;6:63 I http://dx.doi.org/10.20517/2394-5079.2020.60

A B

C

Figure 4. Peripheral Arterial Phase Hyperenhancement. Axial T1-weighted fat saturated MR images of the abdomen prior to (A), and
during the arterial phase (B) and delayed phase (C) of dynamic post extracellular contrast images. The 26 mm observation in the right
hepatic lobe demonstrates peripheral arterial phase hyperenhancement (white arrow). This feature does not qualify as the major feature
of nonrim arterial phase hyperenhancement and should lead the radiologist to assign the category of LR-M (probably or definitely
malignancy, but not HCC specific). HCC: hepatocellular carcinoma

alterations can often vary in size from one exam to the next. Also, the comparison prior examination must
be a CT or MRI exam that was performed 6 months or less prior to the more recent study [Figure 6]. This
definition of threshold growth is different from prior versions of LI-RADS and was changed to achieve
[18]
congruence with the definition of threshold growth used by the OPTN . Note that the development of a
new observation within 6 months of a prior examination is not considered threshold growth in LI-RADS,
as the definition requires that the observation was present on the prior exam.

Ancillary features
Ancillary features are those imaging features that can be used to change the LI-RADS category of an
observation after the application of major features. Ancillary features can change the category by one
category to reflect either a higher or lower suspicion of malignancy. Ancillary features cannot, however,
be used to change the category of an observation from LR-4 to LR-5. Only major features may be used