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Background
After initial sonographic evaluation, approximately one-fourth of adnexal masses remain indeterminate. MRI act as a problem-solving tool in this scenario. It clearly differentiates the pedunculated myomas or fallopian tube lesions from true ovarian lesions, decreasing the number of false-positive lesions and avoiding unnecessary surgery in benign lesions. The number of adnexal lesions that remain indeterminate after MRI is 5–7%, with high sensitivity and specificity for characterizing both benign and malignant lesions with a PPV for malignancy up to 70% and NPV of 98%.

Educational Goals / Teaching Points
In this education exhibit, we discuss the applicability of O-RADS in adnexal masses. We would discuss the role of MRI in evaluation of adnexal masses. We will explain the MRI sequences, including dynamic contrast-enhanced studies and proper interpretation of these sequences for classifying the adnexal masses in different O-RADS categories. We will discuss, with example, the role of MR in downgrading or upgrading the lesion after primary evaluation by USG for high-risk or indeterminate lesions. We will also discuss special scenarios and how to apply O-RADS in these settings, such as patients with previous hysterectomy with adnexal lesion.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Due to high soft tissue contrast and multiplanar capability, MRI clearly differentiates true ovarian masses from other nonovarian lesions, such as myomas or fallopian tube lesions. Hemorrhage and fat content of an adnexal mass are clearly identified by specific characteristics in the various sequences increasing the specificity of MRI. Small papillary projections in large cystic lesions are difficult to identify on ultrasound, whereas MRI can help identify these lesions irrespective of size of cyst. Optimal MRI protocol with high b value diffusion studies and dynamic contrast-enhanced sequences of 15-second time resolution is of paramount importance.

Conclusion
This educational exhibit can give an overview of indication, technique, and outline of MRI O-RADS descriptors and classifications. It also emphasizes the special clinical scenarios and practical tips while interpreting the MRI of adnexal lesions. The benefits of an accurate diagnosis include the possibility for a woman with high risk for malignancy to be referred to a gynecologic oncologist for appropriate surgical staging and/or cytoreductive surgery and avoidance of unnecessary surgery in low-risk adnexal masses.