Adnexal Lesions: O-RADS MRI

Adnexal Lesions: O-RADS MRI

ORADS MRI Summary

Peritoneal nodularity or irregular thickening ORADS 5
NO peritoneal nodularity or irregular thickening Follicle or corpus luteum or hemorrhagic cyst <3cm in premenopausal women ORADS 1
NOT follicle or corpus luteum or hemorrhagic cyst <3cm in premenopausal women Lipid content NO large volume enhancing solid tissue ORADS 2
Large volume enhancing solid tissue ORADS 4
NO lipid content NO enhancing solid tissue Unilocular cyst NO wall enhancement ORADS 2
Wall enhancement Simple or endometriotic fluid ORADS 2
Proteinaceous, hemorrhagic, or mucinous fluid ORADS 3
Multilocular cyst ORADS 3
Enhancing solid tissue (papillary projection, mural nodule, irregular septation/wall, larger solid portions) Homogeneously T2 and DWI dark ORADS 2
NOT T2/DWI dark DCE: Low Risk TIC ORADS 3
DCE: Intermediate Risk TIC
Non-DCE: Hypo/isoenhancing to myometrium at 30-40s
ORADS 4
DCE: High Risk TIC
Non-DCE: Hyperenhancing to myometrium at 30-40s
ORADS 5

Quick Links:

O-RADS MRI Key Lexicon Terms

1. Major Categories

Category Term Definition Example

1a. Physiological observations
(consistent with normal ovarian physiology)

Follicle Simple cyst ≤ 3 cm in pre-menopausal women. A follicle is hyperintense on T2WI, hypointense on T1WI, and does not enhance. O-RADS MRI, Physiological observations, Follicle
Corpus luteum (CL) Cyst ≤ 3 cm with an enhancing crenulated wall on subtracted post-contrast T1WI, +/- blood flow or hemorrhagic contents. O-RADS MRI, Physiological observations, Corpus Luteum (CL)
1b. Lesions
(not physiologic)
Unilocular Cyst Single locule, without or without solid tissue. O-RADS MRI, Lesions, Unilocular Cyst
Multilocular Cyst More than one locule, with or without solid tissue. O-RADS MRI, Lesions Multilocular Cyst
Solid tissue Conforms to one of the following morphologies and enhances: papillary formations, mural nodules, irregular cyst wall/septations, and solid portion. See below
Other solid components, not considered solid tissue Smooth wall/septation, clot/debris/fat See below

2. Size

Category Term Definition
  Maximum diameter Largest diameter of the lesion and/or solid component in any imaging plane.

3. Shape or Contour of Solid Lesion or Solid Tissue

Category Term Definition Example
3a. Smooth Regular or even margin of a solid lesion or solid tissue O-RADS MRI, Shape or contour of solid lesion or solid tissue, Smooth
3b. Irregular Uneven margin of a solid lesion or solid tissue O-RADS MRI, Shape or contour of solid lesion or solid tissue, Irregular

4. Signal Intensity

Category Term Definition
4a. Homogenous  
Heterogeneous  
4b. T2 Hypointense Signal intensity ≤ iliopsoas muscle
T2 Intermediate Signal intensity between that of iliopsoas muscle and CSF
T2 Hyperintense Signal intensity ≥ CSF
4c. T1 Hypointense Signal intensity that of simple fluid
T1 Intermediate Signal intensity ≥ iliopsoas muscle but < fat
T1 Hyperintense Signal intensity ≥ fat
4d. DWI High B-value Low signal Adnexal lesion with signal similar to urine or cerebral spinal fluid
DWI High B-value High signal Adnexal lesion with signal clearly higher than urine or CSF

5. Lesion Components

Category Term Definition Example
5a. Cystic fluid descriptors Simple fluid Fluid content that follows CSF or urine on all sequences: hyperintense on T2WI and hypointense on T1W1 O-RADS MRI, Cystic fluid descriptors, Simple Fluid
Hemorrhagic fluid Content can be variable depending on age O-RADS MRI, Cystic fluid descriptors, Hemorrhagic Fluid
Fluid-fluid level Appearance when the non-dependent fluid component has a different signal intensity from the dependent fluid component with horizontal delineation (blue arrow)
Endometriotic fluid Content is hypointense on T2WI and hyperintense on T1WI  
Shading Cyst fluid that is hypointense on T2WI; the extent of hypointense T2 signal intensity may be homogenous, variable within the cyst or graduated and dependent O-RADS MRI, Cystic fluid descriptors, Shading
Proteinaceous fluid Content is variable on T2WI and variably hypointense on T1WI O-RADS MRI, Cystic fluid descriptors Proteinaceous Fluid
Fat or lipid containing fluid Hyperintense on T2WI and hyperintense on T1WI, and loses signal on fat saturated images O-RADS MRI, Cystic fluid descriptors, Fat or lipid containing fluid
5b. Solid tissue descriptors
(solid tissue enhances and conforms to one of the listed morphologies)
Papillary projection Enhancing solid component arising from the inner/outer wall or septation of an adnexal lesion, with a branching architecture O-RADS MRI, Solid tissue descriptors, Papillary projection
Mural nodule Enhancing solid component, measuring ≥ 3 mm, arising from the wall or septation of an adnexal lesion, with nodular appearance O-RADS MRI, Solid tissue descriptors, Mural nodule
Irregular septation Enhancing linear strand that runs from one internal surface of the cyst to the contralateral side demonstrating an uneven margin (blue arrow) O-RADS MRI, Solid tissue descriptors, Irregular septation

Larger solid portion

Enhancing component of an adnexal lesion that does not fit into the categories of papillary projection, mural nodule, or irregular septation/wall (orange arrow)
Irregular wall Enhancing cyst wall demonstrating an uneven margin O-RADS MRI, Solid tissue descriptors, Irregular wall
Other solid components, not considered solid tissue Smooth septations/wall Even contour or margin with no irregularities, mural nodules or papillary projections O-RADS MRI, Physiological observations, Smooth septations/wall
Blood, clot, non-enhancing debris and fibrin strands Solid-appearing material within a cyst that does not enhance O-RADS MRI, Physiological observations, Blood, clot, non-enhancing debris and fibrin strands
Fat Lipid-containing material that does not enhance

O-RADS MRI, Physiological observations, Fat

O-RADS MRI, Physiological observations, Hair, calcification, and a Rokitansky nodule

Hair, calcification, and a Rokitansky nodule Other components of a dermoid not considered solid tissue

6. Enhancement: T1W1 post-contrast

6a. Dynamic contrast enhancement with time intensity curves Low risk curve Solid tissue shows minimal and gradual increase in enhancement over time with no well-defined shoulder and no plateau O-RADS MRI, Enhancement: T1W1 post-contrast, Dynamic contrast enhancement with time intensity curves
Intermediate risk curve Enhancement of the solid tissue within the adnexal lesion with an initial slope less than the myometrium, moderate increase in signal intensity with a plateau
High risk curve Enhancement of the solid tissue within the adnexal lesion with an initial slope greater than the myometrium, marked increase in signal intensity with a plateau
6b. Non-dynamic contrast enhancement at 30-40 seconds post-injection Less than or equal to the myometrium Enhancement of the solid tissue within the adnexal lesion (blue arrow) is hypoenhancing to the outer myometrium (orange arrow) at 30-40 seconds post-contrast injection O-RADS MRI, Less than or equal to the myometrium
Greater than myometrium Enhancement of the solid tissue within the adnexal lesion (blue arrow) is equal to or greater than the outer myometrium (orange arrow) at 30-40 seconds post-contrast injection O-RADS MRI, Greater than myometrium

7. General and Extra-Ovarian Findings

7a. Peritoneal fluid Physiologic Small amount of fluid inside the pouch of Douglas or cul-de-sac or between the uterus and bladder  
Ascites Fluid outside the pouch of Douglas or cul-de-sac or fluid extending beyond the space between the uterus and bladder  
7b. Fallopian tube descriptors Tubular Substantially longer in one dimension than in the two perpendicular dimensions O-RADS MRI, Fallopian tube descriptors, Tubular
Endosalpingeal folds Incomplete septations or short round projections, orthogonal to the length of the tube
7c. Peritoneal inclusion cyst Cyst following contour of adjacent pelvic organs; or normal ovary at the edge of/or surrounded by a cystic mass O-RADS MRI, Fallopian tube descriptors, Peritoneal inclusion cyst
7d. Ovarian torsion Twisted pedicle Swirling appearance of the broad ligament or ovarian pedicle O-RADS MRI, Fallopian tube descriptors, Ovarian torsion, Twisted pedicle
Massive ovarian edema Enlarged ovary with edematous central stroma O-RADS MRI, Fallopian tube descriptors, Ovarian torsion, Massive ovarian edema
Ovarian infarction Lack of enhancement of the ovary on T1WI post-contrast (blue arrow; orange arrow shows normal left ovary for reference) O-RADS MRI, Fallopian tube descriptors, Ovarian torsion, Ovarian infarction
7e. Peritoneal thickening, nodules Thickening, smooth Uniform thickening, without focal nodularity  
Thickening, irregularity Nonuniform thickening or focal areas of nodularity  

O-RADS MRI Categories and Risk Stratification

  • O-RADS MRI 0: An incomplete evaluation
  • O-RADS MRI 1: Normal Ovaries
    • No ovarian lesion
    • Ovarian follicle, defined as a 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 (<0.5% risk of malignancy)
    • Unilocular cyst with no enhancing solid tissue**
      • If no wall enhancement, may have any type of fluid content
      • If smooth wall enhancement, may have simple or endometriotic fluid content
    • Lesion with lipid content and:
      • No enhancing solid tissue
      • Only minimal enhancement of the Rokitansky nodule
    • Lesion with homogenously hypointense solid tissue on T2WI and DWI
    • Dilated fallopian tube with simple fluid content (hydrosalpinx) but no enhancing solid tissue. May have a thin, smooth wall/endosalpingeal folds with enhancement.
    • Para-ovarian cyst with no enhancing solid tissue. May have any type of fluid content, and may have a thin, smooth wall +/- enhancement.
  • O-RADS MRI 3: Low risk of malignancy (~ 5%) 
    • Unilocular cyst with no enhancing solid tissue, smooth wall enhancement, and proteinaceous, hemorrhagic, or mucinous fluid content
    • Multilocular cyst with no enhancing solid tissue or lipid content. May have any type of fluid content, and may have smooth septae and wall with enhancement
    • Lesion with solid tissue (excluding T2 and DWI dark) with low-risk time intensity curve on DCE MRI***
    • Dilated fallopian tube with no enhancing soft tissue nodule and:
      • Non-simple fluid and thin walls/folds
      • Simple fluid with thick, smooth walls/folds
  • O-RADS MRI 4: Intermediate risk of malignancy (~ 50%) 
    • Lesion with solid enhancing tissue (excluding T2 and DWI dark) with:
      • Intermediate-risk time intensity curve on DCE MRI****
      • If DCE MRI is not feasible, any lesion with enhancement ≤ myometrium at 30-40s on non-DCE MRI
    • Lesion with lipid content and large volume enhancing solid tissue
  • O-RADS MRI 5: High risk of malignancy (~ 90%)
    • Lesion with solid tissue (excluding T2 and DWI dark with:
      • High-risk time intensity curve on DCE MRI*****
      • If DCE MRi is not feasible, any lesion with enhancement > myometrium at 30-40s on non-DCE MRI
    • Peritoneal, mesenteric, or omental nodularity or irregular thickening with or without ascites

*Women are categorized as pre- or postmenopausal, with postmenopausal defined as ≥ 1 year of amenorrhea
**Solid tissue is defined as a lesion component that enhances and has one of the following morphologies: papillary projection, mural nodule, irregular septation/wall, or other larger solid portions that do not conform to the aforementioned morphologies.
***Low-risk curve = minimal and gradual increase in signal over time with no well-defined shoulder and no plateau
****Intermediate-risk curve = initial slope less than myometrium, moderate increase in signal intensity with a plateau
*****High-risk curve = initial slope greater than myometrium, marked increase in signal intensity with a plateau

When lesions can be confidently diagnosed by MRI features, the final radiological diagnosis can be reported without an O-RADS risk stratification score assigned. 

An online O-RADS MRI calculator tool2 to aid in lesion characterization and O-RADS MRI assignment can be found at http://www.oradsmricalc.com.

O-RADS MRI Dictation

Adnexal Findings:

For each adnexal lesion, describe:

  • Size: Maximum diameter in any plane
  • Morphology:
    • Unilocular cyst without solid component
    • Multilocular cyst without solid component
    • Cystic with solid component
    • Solid
  • Cystic component (if applicable):
    • Fluid descriptors: simple; non-simple fluid (hemorrhagic, endometriotic, proteinaceous, fat or lipid-containing).
    • Signal descriptors: homogeneous; heterogeneous
    • If present, describe fluid-fluid level/shading and smooth wall or septal enhancement.
  • Solid tissue (if applicable):
    • Solid tissue descriptors: irregular septation or wall; papillary projection; mural nodule; large solid tissue
    • Signal descriptors: T2 intensity; high b value DWI signal; enhancement less than/equal to OR greater than outer myometrium at 30-40 seconds post-contrast injection
  • Other solid component (if applicable):
    • Smooth wall/septation, clot/debris, fat, hair, calcification, Rokitansky nodule
  • Lipid component: Describe if present

Extra-adnexal Findings:

If present, include: ascites; peritoneal or omental stranding, thickening or nodularity.

Impression:

Lesion 1: ____. (O-RADS MRI __).
Lesion 2: ____. (O-RADS MRI __).

O-RADS MRI (Ovarian Imaging Reporting and Data System) assessment utilizes a 5-point scale to indicate the likelihood of malignancy based on a combination of multi-parametric MRI findings.

O-RADS MRI 0: Incomplete evaluation.
O-RADS MRI 1: Normal ovaries.
O-RADS MRI 2: Almost certainly benign (<0.5% PPV for malignancy).
O-RADS MRI 3: Low risk (~5% PPV for malignancy).
O-RADS MRI 4: Intermediate risk (~50% PPV for malignancy).
O-RADS MRI 5: High risk (~90% PPV for malignancy).

PPV = positive predictive value

Reference: Thomassin-Naggara I, Poncelet E, Jalaguier-Coudray A, et la. Ovarian-adnexal reporting data system magnetic resonance imaging (O-RADS MRI) score for risk stratification of sonographically indeterminate adnexal masses. JAMA Netw Open. 2020;3(1):e1919896.

Example Cases

Case 1

O-RADS MRI, Example cases 1

Lexicon Terms: Cystic lesion; non-simple fluid – fat or lipid-containing fluid; without solid tissue
Report Impression: Bilateral cystic lesions with lipid content without enhancing solid tissue, compatible with O-RADS MRI score 2 (almost certainly benign).
Pathology: Bilateral dermoid cysts. 

O-RADS MRI, Score 2

Case 2

O-RADS MRI, Example case 2

Lexicon Terms: Cystic lesion; non-simple fluid – hemorrhagic fluid; solid tissue - mural nodule; tubular
Report Impression: Cystic adnexal lesion with solid tissue that enhances less than the outer myometrium, compatible with O-RADS MRI score 4 (intermediate risk).
Pathology: Serous adenocarcinoma likely arising from the fallopian tube. 

O-RADS MRI Score 4

Case 3

O-RADS MRI Example 3

Lexicon Terms: Cystic lesion; simple  fluid; solid tissue – mural nodule
Report Impression: Cystic adnexal lesion with enhancing solid tissue (mural nodule). Given enhancement less than the uterine myometrium, the lesion is classified as O-RADS MRI 4.
Pathology: Borderline serous cystadenoma.

O-RADS MRI Score 4

Case 4

O-RADS MRI Score 4

Lexicon Terms: Solid lesion; smooth shape/contour; heterogeneous; T2 hyperintense; T1 hypointense; peritoneal nodules
Report Impression: Adnexal lesion with solid tissue and peritoneal nodularity, compatible with O-RADS MRI score 5 (high risk).
Pathology: Borderline serous cystadenoma.

O-RADS MRI Score 5

Reference

  1. Thomassin-Naggara I, Poncelet E, Jalaguier-Coudray A, et la. Ovarian-adnexal reporting data system magnetic resonance imaging (O-RADS MRI) score for risk stratification of sonographically indeterminate adnexal masses. JAMA Netw Open. 2020;3(1):e1919896.
  2. O-RADS MRI Lexicon Categories, Terms and Definitions. Release date: November 2002. https://www.acr.org/-/media/ACR/Files/RADS/O-RADS/O-RADS-MR-Lexicon-Terms-Table-November-2020.pdf
  3. O-RADS MRI Stratification System Table. Release date: September 2020. https://www.acr.org/-/media/ACR/Files/RADS/O-RADS/O-RADS-MR-Risk-Stratification-System-Table-September-2020.pdf

CME credit information

Release Date: September 7, 2022
Expiration Date: September 7, 2023
Description: Educational website with high-yield educational information and abundant imagingexamples authored by Dr.Krista Suarez-Weiss
Faculty:

Course Directors:
Ramin Khorasani, MD, MPH
Vice Chair, Department of Radiology, Brigham and Women’s Hospital
Professor, Harvard Medical School

Sanjay Saini, MD
Vice Chair, Department of Radiology, Massachusetts General Hospital
Professor of Radiology, Harvard Medical School 

Authors:
Kristine S. Burk, MD
Department of Radiology, Brigham and Women's Hospital
Instructor in Radiology, Harvard Medical School

Krista Suarez-Weiss, MD
Clinical Instructor, Harvard Medical School
Resident Liaison, Cross-Sectional Interventional Radiology, Brigham and Women's Hospital

Atul B. Shinagare, MD
Department of Radiology, Brigham and Women's Hospital
Associate Professor of Radiology, Harvard Medical School
Chief, Abdominal Imaging and Intervention, Brigham Health
Interim Chief, Cancer Imaging, Dana-Farber Cancer Institute

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Ramin Khorasani, MD, MPH
Kathryn Nardozza
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Consultant: Imaging Endpoints; Virtualscopics

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Krista Suarez-Weiss,MD

The following speakers have reported relevant financial relationships with an ineligible company:
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Consultant: Imaging Endpoints; Virtualscopics

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