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Editorial for “Added‐Value of Quantitative Analysis of Diffusion‐Weighted Imaging in Ovarian‐Adnexal Reporting and Data System Magnetic Resonance Imaging (O‐RADS MRI): A Prospective Cohort Study”

Editorial for “Added-Value of Quantitative Analysis of Diffusion-Weighted Imaging in Ovarian-Adnexal Reporting and Data System Magnetic Resonance Imaging (O-RADS MRI): A Prospective Cohort Study” Ovarian cancer is the third most common gynecological malignancy, with the highest mortality among all gynecological malignancies. Ultrasound is the primary imaging modality in detecting ovarian malignancy. Approximately 18%–31% of adnexal lesions remain indeterminate in ultrasound examination. The O-RADS MRI (ovarian-adnexal reporting and data system magnetic resonance imaging) serves as a supplementary examination after ultrasound, which could correctly reclassify most of the ultrasound-indeterminate adnexal masses. However, there are 10.8%–12.5% of masses left to be unclassified. In recent years, quantitative imaging biomarkers have emerged and validated to improve the diagnostic performance of O-RADS MRI. For ovarian mases, the most common reported imaging biomarkers were different coefficients calculated from quantitative diffusion-weighted MRI, especially the apparent diffusion coefficient (ADC) value. However, it remains controversial on the diagnostic contribution of these imaging biomarkers for differentiating malignant and benign ovarian lesions. First, performing diffusion-weighted MRI in ovarian lesions is a great challenge, because of the highly heterogeneous compositions in ovarian lesions, including the cysts filled with mucous or serous fluid, and different solid components such as lipid and hemorrhage. The mean ADC value from the whole lesion is closer to the high value of massive cystic components, rather than the low value of any small malignant portion. Additionally, diffusion-weighted MRI variables, similar to other quantitative imaging biomarkers, might vary between scanners and the sequence parameters. Therefore, despite the significant efforts in developing and validating diffusion-weighted coefficients, no standard reference of diffusion-weighted coefficients has been adopted in standard clinical practice. This is the first study that integrated ADC values and O-RADS MRI for risk stratification. In this issue of JMRI, the authors investigated the performance of ADC values of whole lesion and targeted component separately in preoperatively discriminating the benign and malignant ovarian lesions especially from the O-RADS score 4 group. Inconsistent with the previous reports about the considerable overlap of the ADC values between benign and malignant ovarian lesions, this study found significantly higher ADC values in benign compared to malignant lesions. The plausible reason might be that the main impediment to the discriminative value of ADC, namely benign lesions with massive fatty or cystic contents, has been preliminarily eliminated by O-RADS stratification. In this study, the authors used two approaches to quantify the ADC values of the ovarian lesions, including two-dimensional (2D) delineation and three-dimensional (3D) delineation. The 3D delineation encompassed the whole mass and then generated the mean ADC of the whole lesion. To avoid the falsely higher ADC values in lesions with small proportions of solid components, a manually 2D region of interest (ROI) was also delineated to select those voxels with the highest diffusion restriction in the substructures. Based on these two delineations, two thresholds were established to differentiate malignant from benign lesions in the O-RADS score 4 group, and both were proved to be useful. They showed significant improvement of the discriminative performance of O-RADS score after integrating these ADC thresholds in score of 4 (the area under the curve difference: 0.016; 95% CI: 0.027, 0.006; P = 0.002). The predominated limitation of this study is the relatively small sample size with only 42 lesions of O-RADS score 4. Besides that, no validation cohort was used to validate the diagnostic performance of O-RADS combined with