Improving O-RADS Classification with ADC Mapping: Enhanced MRI-Based Characterization of Adnexal Masses

<ns3:p>Background Ovarian tumors remain one of the most lethal gynecological malignancies due to delayed diagnosis. Differentiating benign from malignant adnexal masses is crucial to guide clinical management. While ultrasound is the first-line imaging modality, its limitations in certain indeterminate cases justify the use of MRI, particularly through the O-RADS classification (Ovarian-Adnexal Reporting and Data System). However, challenges remain in interpreting solid components and enhancement curves. Methods This retrospective study included 89 patients with 116 adnexal masses deemed indeterminate on ultrasound. All patients underwent pelvic MRI using a standardized protocol, including diffusion-weighted imaging (DWI) and ADC mapping. Adnexal masses were classified according to O-RADS, and ADC values were used to refine classifications between categories 3–4 and 4–5. Final diagnoses were confirmed by histopathological analysis after surgical resection. Results Integration of ADC values improved diagnostic accuracy. Six masses initially classified as O-RADS 3 were upgraded to O-RADS 4 based on ADC cut-offs, and 18 O-RADS 4 masses were reclassified as O-RADS 5. Additionally, eight lesions initially classified as O-RADS 4 were reclassified to O-RADS 3. The integrated O-RADS/ADC strategy demonstrated excellent diagnostic performance, with sensitivity reaching 100%, specificity of 95.1%, positive predictive value (PPV) of 97.4%, and negative predictive value (NPV) of 100%. The diagnostic accuracy, calculated using Youden’s index, was 0.95. Furthermore, the use of non-contrast-enhanced MRI sequences (T2-weighted imaging, DWI, and ADC mapping) alone also provided robust diagnostic performance, achieving a sensitivity of 98.67% and a specificity of 90.48%. Conclusions: Incorporating ADC values into the O-RADS classification enhances the diagnostic performance of MRI in evaluating adnexal masses. This refined approach enables more accurate stratification of malignancy risk, improves clinical decision-making, and may help avoid unnecessary surgery, particularly in women where fertility preservation is a concern.</ns3:p>