Assessment of colorectal liver metastases using MRI and CT: impact of observer experience on diagnostic performance and inter-observer reproducibility with histopathological correlation.

INTRODUCTION To compare the diagnostic performance and inter-observer reproducibility of CT and MRI in detecting colorectal liver metastases (CRLM) of observers with different levels of experience. MATERIALS AND METHODS Data from 51 CT and 54 MRI examinations of 105 patients with CRLM were analysed. Intraoperative and histopathological findings served as the reference standard. Analyses were performed by four observers with varying levels of experience regarding imaging of CRLM (reviewers A, B, C and D with respectively >20, >5, <1 and 0 years of experience). Per-segment sensitivity, specificity, Cohen's kappa (κ) for diagnosed segments and Intra-class Correlation Coefficients (ICC) for reported number of lesions were calculated. RESULTS CT sensitivity and specificity was for reviewer A 89.71%/94.41%, B 78.50%/88.37%, C 63.55%/85.58%, D 84.11%/78.60% and regarding MRI A 90.40%/95.43%, B 74.40%/90.04%, C 60.00%/85.89% and D 65.60%/75.90%. The overall inter-observer agreement was higher for CT (κ=0.43, p<0.001; ICC=0.75, p<0.001) than MRI (κ=0.38, p<0.001; ICC=0.65, p<0.001). The experienced reviewers A and B achieved better agreement for MRI (κ=0.54, p<0.001; ICC=0.77, p<0.001) than CT (κ=0.52, p<0.00; ICC=0.76, p<0.001) unlike the less experienced C and D (MRI κ=0.38, ICC=0.63 and CT κ=0.41, ICC=0.74, respectively, p<0.001). CONCLUSIONS The proficiency in detection of CRLM is significantly influenced by observer experience, although CT interpretation is less affected than MRI analysis.