O-RADS MRI Risk Stratification System: Guide for Assessing Adnexal Lesions from the ACR O-RADS Committee

Abstract

MRI plays an important role as a secondary test or problem-solving modality in the evaluation of adnexal lesions depicted at US. MRI has increased specificity compared with US, decreasing the number of false-positive diagnoses for malignancy and thereby avoiding unnecessary or over-extensive surgery in patients with benign lesions or borderline tumors, while women with possible malignancies can be expeditiously referred for oncologic surgical evaluation. The Ovarian-Adnexal Reporting and Data System (O-RADS) MRI Committee is an international collaborative effort formed under the direction of the American College of Radiology and includes a diverse group of experts on adnexal imaging and management who developed the O-RADS MRI risk stratification system. This scoring system assigns a probability of malignancy based on the MRI features of an adnexal lesion and provides information to facilitate optimal patient management. The widespread implementation of a codified reporting system will lead to improved interpretation agreement and standardized communication between radiologists and referring physicians. In addition, it will allow for high-quality multi-institutional collaborations-an important unmet need that has hampered the performance of high-quality research in this area in the past. This article provides guidelines on using the O-RADS MRI risk stratification system in clinical practice, as well as in the educational and research settings.

Graphical abstract

Figure 1:

Image shows Ovarian-Adnexal Reporting and Data System (O-RADS) MRI risk stratification system. DCE = dynamic contrast enhanced, DWI = diffusion-weighted imaging, N/A = not applicable, PPV = positive predictive value. Reprinted, with permission, from the American College of Radiology.

Figure 2:

Graph depicts the visual differences between low-risk, intermediate-risk, and high-risk time-intensity curves (TICs). A low-risk TIC is defined as an increase in the signal intensity of solid tissue after contrast material administration, slower than that in the myometrium, without a well-defined shoulder and no plateau. An intermediate-risk TIC has a moderate initial rise in the signal intensity of solid tissue, with a slope slower than or equal to that of the myometrium, with a shoulder and plateau. A high-risk TIC has a brisk initial rise in the signal intensity of solid tissue, with a slope greater than myometrium, with a shoulder and plateau.

Figure 3:

Image shows examples of Ovarian-Adnexal Reporting and Data System (O-RADS) MRI 1 risk score. * = In postmenopausal women, normal ovaries can contain very small residual follicles, and if the radiologist subjectively assesses the ovaries as normal, the ovaries can be categorized as O-RADS MRI 1. DWI = diffusion-weighted imaging, FS = fat saturated, T1WI = T1-weighted imaging, T2WI = T2-weighted imaging.

Figure 4:

Image shows examples of Ovarian-Adnexal Reporting and Data System (O-RADS) MRI 2 risk score. ^ = Unilocular cysts with simple or hemorrhagic fluid 3 cm or smaller in a premenopausal woman would be classified as O-RADS MRI 1. ^^ = Minimal enhancement of Rokitansky nodule in lesion containing lipid does not change to O-RADS MRI 4. DWI = diffusion-weighted imaging, FS = fat saturated, PPV = positive predictive value, T1WI = T1-weighted imaging, T2WI = T2-weighted imaging.

Figure 5:

Image shows examples of Ovarian-Adnexal Reporting and Data System (O-RADS) MRI 3 risk score. ^^ = Hemorrhagic cyst smaller than 3 cm in a premenopausal woman would be classified as O-RADS MRI 2. DCE = dynamic contrast enhanced, DWI = diffusion-weighted imaging, FS = fat saturated, PPV = positive predictive value, TIC = time-intensity curve, T1WI = T1-weighted imaging, T2WI = T2-weighted imaging.

Figure 6:

Image shows examples of Ovarian-Adnexal Reporting and Data System (O-RADS) MRI 4 risk score. DCE = dynamic contrast enhanced, DWI = diffusion-weighted imaging, FS = fat saturated, PPV = positive predictive value, TIC = time-intensity curve, T1WI = T1-weighted imaging, T2WI = T2-weighted imaging.

Figure 7:

Image shows examples of Ovarian-Adnexal Reporting and Data System (O-RADS) MRI 5 risk score. DCE = dynamic contrast enhanced, DWI = diffusion-weighted imaging, FS = fat saturated, PPV = positive predictive value, TIC = time-intensity curve, T1WI = T1-weighted imaging, T2WI = T2-weighted imaging.