Prostate Imaging for Recurrence Reporting: User Guide.

The Prostate Imaging for Recurrence Reporting (PI-RR) system was introduced in 2021 to standardize the performance and interpretation of pelvic MRI after whole-gland treatment with radical prostatectomy (RP) or radiation therapy (RT). The Prostate Imaging Reporting and Data System (PI-RADS) defines technical and reporting standards for imaging prostate cancer before treatment. Although similar imaging techniques can be applied in assessing the treated prostate gland, the interpretation varies substantially between PI-RADS and PI-RR. With PI-RADS, T2-weighted and diffusion-weighted imaging are emphasized for cancer detection. After treatment, the emphasis shifts in PI-RR to detect recurrence with dynamic contrast enhancement (DCE) imaging. Focal early enhancement on DCE images, and to a lesser degree marked diffusion restriction, are the key MRI findings of recurrence after RP and RT. Using nomenclature similar to that of PI-RADS version 2.1, PI-RR uses established knowledge of recurrent prostate cancer MRI features and systematically codifies scoring elements. The authors discuss the PI-RR rationale, technical standards, and reporting guidelines. The scoring system for posttreatment MRI after RT and RP is reviewed, exploring the relevant T2-weighted, diffusion-weighted, and DCE features for both scenarios. The use of PI-RR is illustrated through instructive cases. Finally, pitfalls in the initial implementation of PI-RR and areas for future development are described. The goal is to provide a comprehensive reference for prostate MRI readers of all experience levels to use PI-RR in standardizing reporting of suspected recurrent prostate cancer. RSNA, 2025 See the invited commentary by Dias and Haider in this issue.