About PI-RADS v2.1
The Prostate Imaging Reporting and Data System (PI-RADS) v2.1 is the current standard for reporting prostate MRI. It provides a structured scoring framework to stratify the likelihood of clinically significant prostate cancer (csPCa), defined as Gleason score ≥7 (grade group ≥2).
Dominant Sequence by Zone
PI-RADS v2.1 uses different dominant sequences depending on lesion location:
- Peripheral Zone (PZ): DWI is the dominant sequence. T2W and DCE are secondary. A DWI score of 3 combined with positive DCE upgrades to PI-RADS 4.
- Transition Zone (TZ): T2W is the dominant sequence. DWI is secondary. A T2W score of 3 combined with DWI ≥4 upgrades to PI-RADS 4.
PI-RADS Assessment Categories
| PI-RADS | Description | csPCa Risk | Management |
|---|---|---|---|
| 1 | Very low suspicion | ≈2% | No targeted biopsy |
| 2 | Low suspicion | ≈6% | No targeted biopsy (consider systematic bx) |
| 3 | Intermediate suspicion | ≈16% | Targeted biopsy or active surveillance (PSA density) |
| 4 | High suspicion | ≈35% | Targeted biopsy recommended |
| 5 | Very high suspicion | ≈60–75% | Targeted biopsy recommended |
mpMRI Components
T2W (T2-weighted imaging) — Structural anatomy. Key sequence for TZ lesions. Suspicious features: hypointense mass with ill-defined margins, disruption of capsule or seminal vesicle.
DWI (Diffusion-weighted imaging) + ADC map — Dominant sequence for PZ lesions. High-grade tumors show restricted diffusion (low ADC, high signal on high b-value). Most sensitive for csPCa.
DCE (Dynamic Contrast Enhancement) — IV contrast series. Positive DCE: early focal enhancement corresponding to the T2W/DWI lesion. Role is adjunct in v2.1 — mainly for upgrading PI-RADS 3 PZ lesions.
References
American College of Radiology. PI-RADS Prostate Imaging – Reporting and Data System, Version 2.1. ACR/ESUR/AdMeTech. 2019.