PI-RADS version 2: what you need to know

Abstract

Prostate cancer is the second most prevalent cancer in men worldwide and its incidence is expected to double by 2030. Multi-parametric magnetic resonance imaging (MRI) incorporating anatomical and functional imaging has now been validated as a means of detecting and characterising prostate tumours and can aid in risk stratification and treatment selection. The European Society of Urogenital Radiology (ESUR) in 2012 established the Prostate Imaging-Reporting and Data System (PI-RADS) guidelines aimed at standardising the acquisition, interpretation and reporting of prostate MRI. Subsequent experience and technical developments have highlighted some limitations, and a joint steering committee formed by the American College of Radiology, ESUR, and the AdMeTech Foundation have recently announced an updated version of the proposals. We summarise the main proposals of PI-RADS version 2, explore the evidence behind the recommendations, and highlight key differences for the benefit of those already familiar with the original.

Copyright © 2015 The Royal College of Radiologists. All rights reserved.

Figures

Figure 1

Importance of clinical context. A 60-year-old man referred for raised PSA. (a) Axial T2WI demonstrates a focal lesion in the left mid PZ (arrows), with matching restricted diffusion (b); PI-RADS score 4. Subsequent transperineal fused TRUS-MRI targeted-biopsy is planned (c), with sagittal US image confirming needle placement in the lesion (d). Histology confirms high-grade PIN. MRI repeated at 18 months shows no change in the previously sampled lesion (e, f). Although the PI-RADS score is based solely on mpMRI findings and remains 4, when taking account of clinical context, the report conclusion would more appropriately state that clinically significant cancer is unlikely to be present.

Figure 2

Differences inT2 scoring for high probability targets. A 77-year-old patient with a PSA of 17 ng/ml. (a)T2W1 shows a large (2.5 × 1.5 cm) lesion centred in the left TZ at the level of the mid-gland (arrow), with matching restricted diffusion (b-c). P1-RADS v1 scores: 4 for T2 as no features of ECE and no broad capsular contact, 5 for DW1. P1-RADS v2 overall score 5: T2 is the dominant sequence and the lesion is >1.5 cm, despite no features of ECE. Subsequent targeted biopsy confirms Gleason 4+5 disease (90% core involvement) in the left medial mid-gland and Gleason 5+5 (60% involvement) in the left posterior lateral gland.

Figure 3

False-positive DCE result, correctly classed as low probability for tumour with PI-RADS v2 criteria. 63 year-old man, serum PSA=2.31 ng/ml. a: T2W1 imaging shows an area of intermediate signal with geographical features in the right mid/apex PZ (arrows) with no matching restricted diffusion (b,c). d: The region shows focal early enhancement on DCE-MRI (arrow), with a Type III curve. PI-RADS v1 scores: 2 for T2, 2 for DWI, 5 for DCE, summed score=9. PI-RADS v2 overall score=2 (DWI is the dominant PZ sequence) despite being “positive” with DCE. Targeted biopsy of this region was benign.

Figure 4

False-negative DCE, correctly evaluated as likely tumour using PI-RADS v2 criteria. 60 year-old patient with a PSA of 4.48 ng/ml. a: T2W1 imaging shows a focal area of intermediate/low signal the right mid/apex PZ (arrows), with marked matching restricted diffusion (b, c). d: The region shows diffuse, but no focal or early enhancement on DCE-MRI (arrow), with a Type I curve. PI-RADS v1 scores: 3 for T2, 5 for DWI, 1 for DCE, summed score=9. PI-RADS v2 overall score=5 (DWI is the dominant PZ sequence) despite being “negative” with DCE. Targeted biopsy demonstrated a Gleason 3+3 tumour in 10% of the cores.

Figure 5

High b-value images aid detection of bone metastases. A 68-year-old man with rising PSA, 2 years post-prostatectomy. (a) Axial T2W1 shows a subtle low intensity area in the left acetabulum (arrow). (b) Axial b=1400 DWI sequence; the lesion demonstrates restricted diffusion and appears more conspicuous on these high b-value images.

Figure 6

Sector maps for division of prostatic regions. A PI-RADS v2 schema incorporating the central zone and utilizing alphabetic abbreviations; PZ, peripheral zone; TZ, transition zone; a, anterior; p, posterior; pm, posteromedial; pl, postero-lateral; AS, anterior stroma. Used with Permission David Rini ©, Johns Hopkins University.