Synopsis

While intra- and inter-observer agreement rates for size measurement is“excellent” for radiologists, variability across imaging phases could potentially impact LI-RADS categorization. Measurement variations were mostly seen across different postcontrast dynamic phases, as well as, related to specific imaging features (eg, presence of APHE and/or a capsule). In our opinion, the standardization of the most adequate imagingphase to perform size measurements of focal liver observations may increase thereproducibility of LI-RADS categories.

Purpose: To evaluate the agreement of size measurements of focal liver observations on MRI and its impact on Liver Imaging Reporting And Data System (LI-RADS) v2017 diagnostic categories.

Methods: Between September 2017 and May 2018, 52 patients with 95 focal liver observations (LI-RADS 3, 4, 5, M) underwent multiarterial-phase MRI at 3T. Images were acquired at nine time points (6 arterial phases, 2, 3, and 10 minutes delay) after injecting 0.1 mmol/kg gadobutrol. Three independent radiologists manually measured the longest diameter of each observation at each imaging phase. Subsequently and in consensus, observations were scored for the presence of LI-RADS major features (arterial phase hyperenhancement (APHE), washout (WO) and capsule (C). Consensus scores were used along with individual diameter measurements to assign a final LI-RADS category. Size measurements in each phase were compared using Spearman’s correlation, intraclass-correlation coefficients and mixed-effect linear regression. Observations that changed LI-RADS categories were grouped in stable and unstable subgroups.

Results: Observations changed LI-RADS categories in relation to size variability, in 5 to 20 (9.8-21.1%) out of 95 depending on the imaging phase in which the measurement was performed. Diameter measurements variability were related to: i) imaging delay (acquisition time post-contrast injection) (p<0.0001), ii) presence of APHE (p=0.0074), iii) presence of C (p=0.0152), and iv) reader (p<0.0001). Overall, intra-reader and inter-reader agreements of size measurements were excellent (CI: 0.935 to CI: 0.990 and CI: 0.938 to CI: 0.970).

Conclusion: Focal liver observations size measurements may show variability across imaging phases that could potentially impact LI-RADS categorization. Standardizing the most adequate time point to measure size may increase reproducibility of LI-RADS categories.

Discussion: While intra- and inter-observer agreement rates for size measurement is “excellent” for radiologists, variability across imaging phases could potentially impact LI-RADS categorization. Measurement variations were mostly seen across different post contrast dynamic phases, as well as, related to specific imaging features (eg, presence of APHE and/or a capsule).

Acknowledgements

References

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