Prostate mpMRI & PI-RADS: What It Shows and When It’s Used
Multiparametric MRI now sits before biopsy in prostate cancer pathways, finding significant disease and safely sparing many men an unnecessary biopsy.
The three parameters
- T2-weighted: anatomy and zonal detail; the dominant sequence for the transition zone.
- Diffusion (DWI/ADC): the dominant sequence for the peripheral zone; restricted diffusion (low ADC) flags cellular tumour.
- Dynamic contrast (DCE): a secondary/tie-breaker showing early enhancement.
PI-RADS v2.1 combines these into a 1–5 score of the likelihood of clinically significant cancer, with a dominant sequence per zone (DWI in peripheral, T2 in transition).
PI-RADS at a glance
| Score | Meaning |
|---|---|
| 1–2 | Clinically significant cancer very unlikely / unlikely |
| 3 | Equivocal: individualise (PSA density, follow-up) |
| 4–5 | Likely / highly likely: targeted biopsy indicated |
MRI also enables MR-targeted (often MRI–ultrasound fusion) biopsy of the suspicious lesion, improving detection of significant disease over systematic biopsy alone.
Practical notes
Quality depends on protocol and reader experience; bowel gas and hip prostheses degrade DWI. PSA density complements PI-RADS 3 decisions. Post-biopsy haemorrhage can mimic tumour, so timing matters.
Sources
- Turkbey B et al. PI-RADS v2.1. Eur Urol 2019;76:340–9. Kasivisvanathan V et al. PRECISION trial. N Engl J Med 2018;378:1767–77.
Educational summary for clinicians; local pathways and guidelines take precedence. Not medical advice.
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