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

Abstract

Objectives

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.

Conclusion

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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Abbreviations

ADC:

Apparent diffusion coefficient

PI-RADSv2:

Prostate Imaging Reporting and Data System version 2

DWI:

Diffusion-weighted imaging

DCE:

Dynamic contrast-enhanced

MR:

Magnetic resonance

TR:

Repetition time

TE:

Echo time

PCa:

Prostate cancer

CSC:

Clinically significant cancer

PZ:

Peripheral zone

TZ:

Transition zone

ECE:

Extracapsular extension

SVI:

Seminal vesicle invasion

ROI:

Region of interest

ROC:

Receiver operating-characteristic

AUC:

Area under the curve

PPV:

Positive predictive value

CI:

confidence interval

PSA:

Prostate-specific antigen

GS:

Gleason score

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Acknowledgements

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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Correspondence to Young Taik Oh.

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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). https://doi.org/10.1007/s00330-016-4678-7

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  • DOI: https://doi.org/10.1007/s00330-016-4678-7

Keywords

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