Purpose

To determine whether reader perception of a capsule affects reader interpretation of washout in hypervascular liver nodules at dynamic magnetic resonance imaging (MRI) in patients at risk for hepatocellular carcinoma (HCC).

Materials and methods

This retrospective study was Institutional Review Board (IRB)-approved and Health Insurance Portability and Accountability Act (HIPAA)-compliant, with waiver of informed consent. MRI reports for 111 hypervascular liver nodules (median 2.0 cm, range 1.0-17.8 cm) in 62 patients were reviewed, and the presence/absence of capsule and washout were recorded for one reading. A second independent study reading was also performed. The signal intensity ratio (SIR) for each nodule and liver parenchyma was measured. An objective SIR threshold was identified for nodules without capsules that correctly classified the presence/absence of washout, then applied to nodules with capsules to classify them as having / not having objective washout. Nodules were categorized as definite / not definite HCC using subjective and objective washout, based on LI-RADS, OPTN, AASLD, and EASL criteria, and proportions compared using McNemar's test.

Results

Agreement on nodule features was high for Readings 1 and 2 (κ = 0.70-0.82). For Reading 1, 71 nodules lacked capsules (43 with and 28 without subjective washout); an SIR threshold of 0.88 classified the presence/absence of washout correctly in 94% (67/71, P < 0.001). Forty nodules had capsules; although all had subjective washout (100%, 40/40), 75% (30/40) had objective washout (P < 0.05). Using objective washout caused 4.5% (3/66; LI-RADS, OPTN) and 12% (10/83; AASLD, EASL) of nodules to be recategorized from definite HCC to not definite HCC.

Conclusion

Reader perception of capsule affects interpretation of washout. This effect can influence nodule categorization using imaging-based diagnostic systems. J. Magn. Reson. Imaging 2016;43:1337-1345.