Non-contrast MRI can accurately characterize adnexal masses: a retrospective study.

Objective: To determine the accuracy of interpretation of a non-contrast MRI protocol in characterizing adnexal masses Methods and Materials: 291 patients (350 adnexal masses) who underwent gynecological MRI at our institution between 1 st January 2008 and 31 th December 2018 were reviewed. A random subset (102 patients with 121 masses) was chosen to evaluate reproducibility and repeatability of readers’ assessments. Readers evaluated non-contrast MRI scans retrospectively, assigned a 5-point score for the risk of malignancy and gave a specific diagnosis. Reference standard for the diagnosis was histopathology or at least one-year imaging follow-up. Diagnostic accuracy of the non-contrast MRI score was calculated. Inter- and intra-reader agreement was analyzed with Cohen’s kappa statistics. Results: There were 53/350 (15.1%) malignant lesions in the whole cohort and 20/121 (16.5%) malignant lesions in the random subset. Good agreement between readers was found for the non-contrast MRI score (к= 0.73, 95% confidence interval [CI] 0.58–0.86) whilst the intra-reader agreement was excellent (к= 0.81, 95% CI 0.70–0.88). The non-contrast MRI score value of ≥4 was associated with malignancy with a sensitivity of 84.9%, specificity of 95.9%, accuracy of 94.2% and a positive likelihood ratio of 21 (area under the receiver operating curve 0.93, 95% CI 0.90–0.96). Conclusion: Adnexal mass characterization on MRI without the administration of contrast medium has a high accuracy and excellent inter- and intra-reader agreement. Our results suggest that non-contrast studies may offer a reasonable diagnostic alternative when administration of intravenous contrast medium is not possible