title: PI-RADS version 2: quantitative analysis aids reliable interpretation of diffusion-weighted imaging for prostate cancer.
abstract: OBJECTIVE
  To determine whether apparent diffusion coefficient (ADC) ratio aids reliable interpretation of diffusion-weighted imaging (DWI) for prostate cancer (PCa).
  
  
  METHODS
  Seventy-six consecutive patients with PCa who underwent DWI and surgery were included. Based on pathologic tumour location, two readers independently performed DWI scoring according to the revised Prostate Imaging Reporting and Data System (PI-RADSv2). ADC ratios of benign to cancerous prostatic tissue were then measured independently and compared between cases showing concordant and discordant DWI scores ≥4. Area under the curve (AUC) and threshold of ADC ratio were analyzed for DWI scores ≥4.
  
  
  RESULTS
  The rate of inter-reader disagreement for DWI score ≥4 was 11.8% (9/76). ADC ratios were higher in concordant vs. discordant DWI scores ≥4 (median, 1.7 vs. 1.1-1.2; p < 0.001). For DWI scores ≥4, the AUCs of ADC ratios were 0.970 for reader 1 and 0.959 for reader 2. In patients with an ADC ratio >1.3, the rate of inter-reader disagreement for DWI score ≥4 decreased to 5.9-6.0%. An ADC ratio >1.3 yielded 100% (reader 1, 54/54; reader 2, 51/51) positive predictive value for clinically significant cancer.
  
  
  CONCLUSIONS
  ADC ratios may be useful for reliable interpretation of DWI score ≥4 in PI-RADSv2.
  
  
  CONCLUSIONS
  • The ADC ratio correlated positively with DWI score of PI-RADSv2. • ADC ratio >1.3 was associated with concordant interpretation of DWI score ≥4. • ADC ratio >1.3 was associated with high PPV for clinically significant cancer. • ADC ratio is useful for reliable interpretation of DWI scoring in PI-RADSv2.
authors.affiliation: Department of Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul, 120-752, Republic of Korea.
authors.forename: Sung Yoon
authors.initials: SY
authors.lastname: Park
authors.affiliation: Department of Pathology, Yonsei University College of Medicine, Seoul, South Korea.|Department of Pathology, Hanyang University College of Medicine, Seoul, South Korea.
authors.forename: Su-Jin
authors.initials: SJ
authors.lastname: Shin
authors.affiliation: Department of Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul, 120-752, Republic of Korea.
authors.forename: Dae Chul
authors.initials: DC
authors.lastname: Jung
authors.affiliation: Department of Pathology, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Nam Hoon
authors.initials: NH
authors.lastname: Cho
authors.affiliation: Department of Urology, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Young Deuk
authors.initials: YD
authors.lastname: Choi
authors.affiliation: Department of Urology, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Koon Ho
authors.initials: KH
authors.lastname: Rha
authors.affiliation: Department of Urology, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Sung Joon
authors.initials: SJ
authors.lastname: Hong
authors.affiliation: Department of Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul, 120-752, Republic of Korea. oytaik@yuhs.ac.
authors.forename: Young Taik
authors.initials: YT
authors.lastname: Oh
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011467:Prostate / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000175:diagnosis*; D015203:Reproducibility of Results; D012189:Retrospective Studies
keywords: Apparent diffusion coefficient; Diffusion-weighted imaging; MRI; PI-RADS; Prostate cancer