O-RADS MRI - Adnexal Mass Classification
O-RADS risk stratification system for adnexal mass evaluation by magnetic resonance imaging.
About the O-RADS MRI System
The O-RADS MRI (Ovarian-Adnexal Reporting and Data System for MRI) is a consensus system to standardize reporting and risk stratification of adnexal masses on MRI. There is no differentiation for pre and post menopause. Scores 0 to 5 correspond to Incomplete Evaluation, Normal Ovaries, Almost Certainly Benign, Low Risk, Intermediate Risk, and High Risk.
O-RADS MRI Categories
Credit American College of Radiology (ACR) (ACR)
O-RADS MRI 0 — Incomplete Evaluation
Risk: Not evaluableLexicon Description
N/A
O-RADS MRI 1 — Normal Ovaries
Risk: NormalLexicon Description
No ovarian lesion
Follicle defined as simple cyst ≤ 3 cm in a premenopausal woman
Hemorrhagic cyst ≤ 3 cm in a premenopausal woman
Corpus luteum +/- hemorrhage ≤ 3 cm in a premenopausal woman
O-RADS MRI 2 — Almost Certainly Benign
Risk: <0.5%PPV for malignancy: <0.5%Lexicon Description
Cyst: Unilocular (any type of fluid content): No wall enhancement, No enhancing solid tissue
Cyst: Unilocular (simple or endometriotic fluid content): Smooth enhancing wall, No enhancing solid tissue
Lesion with lipid content: No enhancing solid tissue
Lesion with "dark T2/dark DWI" solid tissue: Homogeneously hypointense on T2 and DWI
Dilated fallopian tube (simple fluid content): Thin, smooth wall/endosalpingeal folds with enhancement, No enhancing solid tissue
Para-ovarian cyst (any type of fluid): Thin, smooth wall +/- enhancement, No enhancing solid tissue
O-RADS MRI 3 — Low Risk
Risk: ~5%PPV for malignancy: ~5%Lexicon Description
Cyst: Unilocular (proteinaceous, hemorrhagic or mucinous fluid content): Smooth enhancing wall, No enhancing solid tissue
Cyst: Multilocular (Any type of fluid, no lipid content): Smooth septae and wall with enhancement, No enhancing solid tissue
Lesion with solid tissue (excluding T2 dark/DWI dark): Low risk time intensity curve on DCE MRI
Dilated fallopian tube: Non-simple fluid: Thin wall/folds; Simple fluid: Thick, smooth wall/folds; No enhancing solid tissue
O-RADS MRI 4 — Intermediate Risk
Risk: ~50%PPV for malignancy: ~50%Lexicon Description
Lesion with solid tissue (excluding T2 dark/DWI dark): Intermediate risk time intensity curve on DCE MRI. If DCE MRI is not feasible, score 4 is any lesion with solid tissue (excluding T2 dark/DWI dark) that is enhancing ≤ myometrium at 30-40s on non-DCE MRI
Lesion with lipid content: Large volume enhancing solid tissue
O-RADS MRI 5 — High Risk
Risk: ~90%PPV for malignancy: ~90%Lexicon Description
Lesion with solid tissue (excluding T2 dark/DWI dark): High risk time intensity curve on DCE MRI. If DCE MRI is not feasible, score 5 is any lesion with solid tissue (excluding T2 dark/DWI dark) that is enhancing > myometrium at 30-40s on non-DCE MRI
Peritoneal, mesenteric or omental nodularity or irregular thickening with or without ascites
Glossary
DCE
Dynamic Contrast Enhancement – evaluates time-intensity curve of solid tissue enhancement
DWI
Diffusion Weighted Imaging – "T2 dark/DWI dark" tissue is typically benign (endometrioma, dermoid)
Solid tissue
Lesion component that enhances and conforms to specific morphologies: papillary projection, mural nodule, irregular septation/wall or other larger solid portions
Rokitansky nodule
Minimal enhancement of Rokitansky nodules in lesion containing lipid does not change to O-RADS MRI 4
References
Sadowski EA, Thomassin-Naggara I, Rockall A, Maturen KE, Forstner R, Jha P, Nougaret S, Siegelman ES, Reinhold C. O-RADS MRI Risk Stratification System: Guide for Assessing Adnexal Lesions from the ACR O-RADS Committee. Radiology. 2022 Apr;303(1):35-47. doi: 10.1148/radiol.204371. Epub 2022 Jan 18. Erratum in: Radiology. 2023 Jul;308(1):e239017. doi: 10.1148/radiol.239017. PMID: 35040672; PMCID: PMC8962917.
Sadowski EA, Thomassin-Naggara I, Rockall A, Maturen KE, Forstner R, Jha P, Nougaret S, Siegelman ES, Reinhold C. Erratum for: O-RADS MRI Risk Stratification System: Guide for Assessing Adnexal Lesions from the ACR O-RADS Committee. Radiology. 2023 Jul;308(1):e239017. doi: 10.1148/radiol.239017. Erratum for: Radiology. 2022 Apr;303(1):35-47. doi: 10.1148/radiol.204371. PMID: 37489996.