PI-RADS v2.1 Quick Guide
PI-RADS v2.1 is a standardized prostate MRI scoring system used to estimate the likelihood of clinically significant prostate cancer and communicate findings consistently.
The PI-RADS score
| Score | Meaning |
|---|---|
| PI-RADS 1 | Very low suspicion |
| PI-RADS 2 | Low suspicion |
| PI-RADS 3 | Intermediate / equivocal |
| PI-RADS 4 | High suspicion |
| PI-RADS 5 | Very high suspicion |
Peripheral zone: DWI is dominant
Peripheral zone lesions are scored primarily by ADC and high b-value DWI. A focal lesion that is dark on ADC and bright on high b-value DWI is more suspicious than a vague, linear, wedge-shaped, or diffuse abnormality.
Transition zone: T2 is dominant
Transition zone lesions are scored primarily by T2 morphology. Suspicious features include a lenticular or non-circumscribed shape, homogeneous moderate T2 hypointensity, and more invasive behavior. DWI can modify selected borderline TZ lesions, but it is not the dominant sequence.
When does DCE matter?
DCE has a limited but important role. In the peripheral zone, positive focal early enhancement can upgrade an otherwise PI-RADS 3 lesion to PI-RADS 4. DCE generally does not drive transition zone scoring.
Image quality caveat
If DWI or DCE is technically inadequate or not performed, PI-RADS assigns that component an “X.” Inadequate DWI is a major limitation, especially for peripheral-zone assessment. If DWI and DCE are both inadequate or absent, assessment should be limited to staging for extraprostatic extension.
Bottom line
Remember the workflow: DWI drives peripheral zone scoring, T2 drives transition zone scoring, and DCE mainly helps decide whether a peripheral zone PI-RADS 3 lesion should be upgraded. PI-RADS should always be interpreted with the full MRI exam, sequence quality, PSA density, prior biopsy history, and clinical context.