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Background
Ultrasound has limited capacity for assigning risk score to indeterminate adnexal lesions. Positive predictive value (PPV) can range from 7% - 50% in a lesion with worrisome features for malignancy on ultrasound. MRI can help increase the PPV from cancer to 71% and negative predictive value (NPV) to 98%. MRI has capacity to provide more specific diagnoses and reduce the level of suspicion and number of surgeries performed for benign diagnoses.

Educational Goals / Teaching Points
Description of standardized terms and definitions by ACR O-RADS (Ovarian-Adnexal Reporting and Data System) MRI lexicon for assessing and reporting adnexal lesions. MRI Technique including DCE (Dynamic contrast enhancement); TIC (time-intensity curves). Pictorial review of adnexal lesions using O-RADS MRI risk stratification system.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
MRI is a problem-solving modality for evaluation of adnexal lesions detected with ultrasound. The O-RADS MRI risk stratification system is a scoring system that assigns a probability of malignancy based on the MRI features. It improves communication between radiologists and referring clinicians to optimize management. Also, definitive diagnosis of sonographically indeterminate lesions on MRI reduces the level of suspicion and thus unnecessary surgeries performed for benign lesions in asymptomatic women. There are six risk score categories in the O-RADS MRI risk stratification system from O-RADS MRI 0 to O-RADS MRI 5 with increasing PPV for malignancy. Important parameters assessed include fluid components (simple, hemorrhagic, proteinaceous, endometriotic, lipid) and the solid components (solid tissue, clot, debris, fat). Any enhancement of solid tissue suggests the possibility of a neoplastic lesion. DCE enhancement kinetics help stratify the lesion as low, intermediate, or high risk for malignancy. DCE MRI with time-intensity curves (TICs) is preferred as no studies have determined the PPV for malignancy when non-DCE MRI is used.

Conclusion
The ovarian-adnexal reporting and data system MRI risk score provides a standardized means to assign a score to adnexal lesions based on MRI features. It will help in expediting correspondence between radiologists and clinicians in cases with higher risk scores and provide speedy oncologic surgical evaluation. It is an impactful tool for researchers to carry out multi-institutional studies to improve outcomes in women with adnexal lesions.