title: Head-to-head comparison of PI-RADS v2 and PI-RADS v1.
abstract: OBJECTIVE
  To compare the reproducibility and diagnostic performance of PI-RADS version 2 (v2) and version 1 (v1) for the diagnosis of prostate cancer (PCa) on multiparametric MRI.
  
  
  METHODS
  This IRB-approved retrospective study included 65 consecutive biopsy-naïve or biopsy-negative patients suspicious for PCa (mean age: 65 years, mean PSA: 10.8ng/ml) who were undergoing MR-guided biopsy after multiparametric 3T prostate MRI (T2w, DWI, DCE). Two independent readers (R1; R2) scored the prostate lesions according to the v2 score and the v1 sum score. Diagnostic measures (sensitivity, specificity, and area under the ROC-curve) were compared for all cases and stratified by location (transitional zone, TZ, peripheral zone, PZ). Inter-reader agreement was assessed by kappa statistics.
  
  
  RESULTS
  Inter reader agreement for v2 and v1 was substantial to almost perfect (kappa v2: 0.71, v1: 0.81). Overall, sensitivity between both readers and methods did not differ (p>0.05). Overall specificity was higher using v1 compared to v2 (R1: p=0.0078, R2: p=0.0313) In the TZ, v2 showed a higher AUC (0.81-0.84) compared to v1 (AUC 0.77-0.78). Here, the sensitivity of v2 (87.5-100%) was higher than that of v1 (75%) while v2 specificity (50%-56.3%) was lower than that of v1 (68.8-75%). In the PZ, AUCs were higher using v1 (AUC 0.82-0.83) compared to v2 (AUC 0.61-0.63). The specificity for v1 was higher (43.8-62.3%) than that for v2 (12.5-18.8%) while both v2 and v1 achieved 100% sensitivity.
  
  
  CONCLUSIONS
  PI-RADS v2 and v1 inter-reader agreement is excellent, but their diagnostic performance differs. While v2 appears to be the preferable method for the evaluation of TZ lesions, v1 performs better in the PZ.
authors.affiliation: Department of Biomedical Imaging and Image-guided Therapy, Division of Molecular and Gender Imaging, Medical University of Vienna (AKH), Waehringer-Guertel 18-20, A-1090 Wien, Austria.
authors.forename: Stephan
authors.initials: S
authors.lastname: Polanec
authors.affiliation: Department of Biomedical Imaging and Image-guided Therapy, Division of Molecular and Gender Imaging, Medical University of Vienna (AKH), Waehringer-Guertel 18-20, A-1090 Wien, Austria; Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University Vienna (AKH), Waehringer-Guertel 18-20, A-1090 Wien, Austria.
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Helbich
authors.affiliation: Department of Biomedical Imaging and Image-guided Therapy, Division of Molecular and Gender Imaging, Medical University of Vienna (AKH), Waehringer-Guertel 18-20, A-1090 Wien, Austria.
authors.forename: Hubert
authors.initials: H
authors.lastname: Bickel
authors.affiliation: Department of Biomedical Imaging and Image-guided Therapy, Division of Molecular and Gender Imaging, Medical University of Vienna (AKH), Waehringer-Guertel 18-20, A-1090 Wien, Austria.
authors.forename: Katja
authors.initials: K
authors.lastname: Pinker-Domenig
authors.affiliation: Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University Vienna (AKH), Waehringer-Guertel 18-20, A-1090 Wien, Austria; Department of Radiation Oncology, Division of Medical Radiation Physics, Medical University of Vienna (AKH), Waehringer-Guertel 18-20, A-1090 Wien, Austria.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Georg
authors.affiliation: Department of Urology, Medical University of Vienna (AKH), Waehringer-Guertel 18-20, A-1090 Wien, Austria.
authors.forename: Shahrokh F
authors.initials: SF
authors.lastname: Shariat
authors.affiliation: Department of Urology, Confraternität Vienna, Skodagasse 32, A-1080 Wien, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Aulitzky
authors.affiliation: Clinical Institute of Pathology, Medical University of Vienna (AKH), Waehringer-Guertel 18-20, A-1090 Wien, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Susani
authors.affiliation: Department of Biomedical Imaging and Image-guided Therapy, Division of Molecular and Gender Imaging, Medical University of Vienna (AKH), Waehringer-Guertel 18-20, A-1090 Wien, Austria; Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University Vienna (AKH), Waehringer-Guertel 18-20, A-1090 Wien, Austria. Electronic address: pascal.baltzer@meduniwien.ac.at.
authors.forename: Pascal A
authors.initials: PA
authors.lastname: Baltzer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D001706:Biopsy / Q000379:methods; D003430:Cross-Sectional Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011467:Prostate / Q000000981:diagnostic imaging / Q000473:pathology; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D012372:ROC Curve; D011873:Radiology Information Systems / Q000592:standards*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
keywords: Multiparametric MRI; PI-RADS; Prostate cancer; Standardized reporting