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The Ovarian-Adnexal Reporting and Data System (O-RADS) is a standardized risk stratification and management system developed by the American College of Radiology (ACR) for assessing ovarian and adnexal lesions on ultrasound and MRI.

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It aims to improve consistency in reporting and help guide management decisions by providing a clear, evidence-based framework.

Overview of O-RADS Categories

O-RADS assigns a score from 0 to 5 (or 1–5 depending on the modality), reflecting increasing risk of malignancy:

Note: The classification is applied differently based on imaging modality (ultrasound or MRI).

O-RADS Ultrasound Classification

• Based on morphology, vascularity, and solid/cystic components.
• Incorporates IOTA terminology for standardization.
• Categories are determined using a flowchart decision tree, assessing:
  • Lesion type (unilocular cyst, multilocular cyst, solid, etc.)
  • Internal echogenicity (anechoic, echogenic, low-level echoes)
  • Presence of papillary projections, solid components, or septations
  • Doppler flow (color score 1–4)

O-RADS MRI Classification

MRI is used primarily when ultrasound findings are indeterminate or suspicious:

• Uses T1, T2, fat-suppressed, and post-contrast sequences
• Risk assignment is based on:
  • Enhancement characteristics
  • Signal intensities (solid tissue with or without enhancement)
  • Diffusion-weighted imaging (restricted diffusion in solid components)

MRI offers higher specificity, particularly in differentiating benign from malignant lesions when US is inconclusive.

Clinical Utility and Role