Can apparent diffusion coefficient analysis improve the categorization of Ovarian-Adnexal reporting and data system magnetic resonance imaging scores 3, 4, and 5 lesions?

Background Ovarian cancer is the second most common gynecologic malignancy, and accurate characterization of adnexal lesions is essential for management. While ovarian-adnexal reporting and data system magnetic resonance imaging (O-RADS MRI) improves diagnostic performance, indeterminate cases remain challenging. Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) values offer additional functional criteria that may refine O-RADS stratification. This study aimed to assess the added value of ADC measurements in improving the diagnostic accuracy of O-RADS MRI for adnexal lesions. Results This retrospective study included 66 female patients (18 to 67 years, with a mean of 43.9 ± 13.8 years) with 78 MRI-detected ovarian or adnexal lesions categorized as O-RADS 3, 4, or 5. For MRI-based O-RADS scoring, sensitivity, specificity, positive predictive value, negative predictive value, and overall diagnostic accuracy were 88.4%, 88.6%, 90.5%, 86.1%, and 88.5%, respectively. For qualitative diffusion-weighted imaging analysis, the corresponding values were 86.04%, 77.14%, 82.2%, 81.8%, and 82.05%. Quantitative apparent diffusion coefficient analysis yielded a sensitivity, specificity, positive predictive value, negative predictive value, and overall diagnostic accuracy of 86.0%, 82.9%, 86.1%, 82.9%, and 84.6%, respectively, using an ADC cut off value of less than 1.15 × 10⁻ 3 mm 2 /s as determined in this study. For the combined O-RADS and ADC assessment, the corresponding values were 90.7%, 85.7%, 88.6%, 88.2%, and 88.5%, respectively. Conclusions Quantitative DWI using ADC values improves the prediction of malignancy in adnexal lesions, enhancing sensitivity and negative predictive value compared with O-RADS MRI alone. ADC assessment is especially valuable when contrast-enhanced imaging is not feasible and may aid surgical planning; however, caution is needed when interpreting ADC in lesions prone to diffusion pitfalls. These findings support the potential for a future O-RADS classification incorporating diffusion metrics to improve risk stratification.