Ovarian-Adnexal Reporting and Data System Magnetic Resonance Imaging (O-RADS MRI)

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The Ovarian-Adnexal Reporting and Data System Magnetic Resonance Imaging (O-RADS MRI) forms the MRI component of the Ovarian-Adnexal Reporting and Data System (O-RADS). This system aims to ensure that there are uniform unambiguous sonographic and MRI evaluations of ovarian or other adnexal lesions, accurately assigning each lesion to a risk category of malignancy being present, which informs the appropriate management to be instituted.

For ultrasound, see the Ovarian-Adnexal Reporting and Data System Ultrasound (O-RADS US).

O-RADS MRI serves to guide risk stratification for adnexal lesions discovered in average risk women with no acute symptoms. When multiple or bilateral lesions are encountered, each lesion should be characterized separately, with management driven by the lesion with the highest score. For characteristic lesions that can be confidently diagnosed by the MRI features, the final radiologic diagnosis can be reported with the O-RADS MRI category assignment.

Components of the MRI evaluation:

Validation

The O-RADS MRI risk score has been validated in a large prospective multicenter trial in Europe .

Classification

For risk stratification, the O-RADS MRI system uses five categories (O-RADS 1–5), from normal (1) to high risk of malignancy (5).
An O-RADS MRI 0 (zero) category is used for an incomplete evaluation.

O-RADS MRI 1
  • 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
  • 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 high B-value 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

* Solid tissue is defined as a lesion component that enhances and conforms to one of these morphologies: papillary projection, mural nodule, irregular septation/wall or other larger solid portions.

** Minimal enhancement of Rokitansky nodules in a lesion containing lipid does not change to O-RADS MRI 4.

O-RADS MRI 3
  • 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

*** Hemorrhagic cyst ≤3 cm in a premenopausal woman is O-RADS MRI 1.

O-RADS MRI 4
  • lesion with solid tissue (excluding T2 dark/DWI dark):
    • intermediate-risk time-intensity curve on DCE MRI 
    • if DCE MRI is not feasible, O-RADS MRI 4 is any lesion with solid tissue (excluding T2 dark/DWI dark) that is enhancing less than or the same as myometrium at 30-40 sec on non-DCE MRI
  • lesion with lipid content:
    • large volume-enhancing solid tissue
O-RADS MRI 5
  • lesion with solid tissue (excluding T2 dark/DWI dark):
    • high-risk time-intensity curve on DCE MRI 
    • if DCE MRI is not feasible, O-RADS MRI 5 is any lesion with solid tissue (excluding T2 dark/DWI dark) that is enhancing more than myometrium at 30-40 sec on non-DCE MRI
  • peritoneal, mesenteric or omental nodularity or irregular thickening +/-  ascites

Interpretation

  • O-RADS MRI 0: N/A; incomplete evaluation
  • O-RADS MRI 1: N/A; normal ovaries
  • O-RADS MRI 2: <0.5%; almost certainly benign
  • O-RADS MRI 3: ~5%; low risk
  • O-RADS MRI 4: ~50%; intermediate risk
  • O-RADS MRI 5: ~90%; high risk

History and etymology

O-RADS was developed and published in 2018 by an international multidisciplinary committee, comprising clinicians and researchers from the fields of radiology, gynecology, pathology, and gynecologic oncology, and sponsored by the American College of Radiology (ACR). It was originally designed for sonographic evaluation, and in 2020 the system was extended to include MRI evaluation. The O-RADS MRI was an evolution from the AdnexMR Scoring System published in 2012.

See also