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PI-RADS version 2: quantitative analysis aids reliable interpretation of diffusion-weighted imaging for prostate cancer



To determine whether apparent diffusion coefficient (ADC) ratio aids reliable interpretation of diffusion-weighted imaging (DWI) for prostate cancer (PCa).


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.


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.


ADC ratios may be useful for reliable interpretation of DWI score ≥4 in PI-RADSv2.

Key points

The ADC ratio correlated positively with DWI score of PI-RADSv2.

ADC ratio >1.3 was associated with concordant interpretation of DWI score4.

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.

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Apparent diffusion coefficient


Prostate Imaging Reporting and Data System version 2


Diffusion-weighted imaging


Dynamic contrast-enhanced


Magnetic resonance


Repetition time


Echo time


Prostate cancer


Clinically significant cancer


Peripheral zone


Transition zone


Extracapsular extension


Seminal vesicle invasion


Region of interest


Receiver operating-characteristic


Area under the curve


Positive predictive value


confidence interval


Prostate-specific antigen


Gleason score


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The scientific guarantor of this publication is Young Taik Oh. The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article. The authors state that this work has not received any funding. No complex statistical methods were necessary for this paper. Institutional Review Board approval was obtained. Written informed consent was waived by the Institutional Review Board. Methodology: retrospective, cross sectional study, performed at one institution.

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Park, S.Y., Shin, SJ., Jung, D.C. et al. PI-RADS version 2: quantitative analysis aids reliable interpretation of diffusion-weighted imaging for prostate cancer. Eur Radiol 27, 2776–2783 (2017).

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  • Diffusion-weighted imaging
  • Apparent diffusion coefficient
  • MRI
  • Prostate cancer