Diffusion-weighted imaging of the prostate: should we use quantitative metrics to better characterize focal lesions originating in the peripheral zone?
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To compare inter-reader concordance and accuracy of qualitative diffusion-weighted (DW) PIRADSv2.0 score with those of quantitative DW-MRI for the diagnosis of peripheral zone prostate cancer.
Materials and methods
Two radiologists independently assigned a DW-MRI-PIRADS score to 92 PZ-foci, in 74 patients (64.3±5.6 years old; median PSA level: 8 ng/ml, normal DRE in 70 men). A standardised ADCmean and nine ADC-derived parameters were measured, including ADCratios with the whole-prostate (WP-ADCratio) or the mirror-PZ (mirror-ADCratio) as reference areas. Surgical histology and MRI-TRUS fusion-biopsy were the reference for tumours and benign foci, respectively. Inter-reader agreement was assessed by the Cohen-kappa-coefficient and the intraclass correlation coefficient (ICC). Univariate-multivariate regressions determined the most predictive factor for cancer.
Fifty lesions were malignant. Inter-reader concordance was fair for qualitative assessment, but excellent for quantitative assessment for all quantitative variables. At univariate analysis, ADCmean, WP-ADCratio and WL-ADCmean performed equally, but significantly better than the mirror-ADCratio (p<0.001). At multivariate analysis, the only independent variable significantly associated with malignancy was the whole-prostate-ADCratio. At a cut-off value of 0.68, sensitivity was 94–90 % and specificity was 60–38 % for readers 1 and 2, respectively.
The whole-prostate-ADCratio improved the qualitative inter-reader concordance and characterisation of focal PZ-lesions.
• Inter-reader concordance of DW PI-RADSv2.0 score for PZ lesions was only fair.
• Using a standardised ADCmean measurement and derived DW-quantitative parameters, concordance was excellent.
• The whole-prostate ADCratio performed significantly better than the mirror-ADCratio for cancer detection.
• At a cut-off of 0.68, sensitivity values of WP-ADCratio were 94–90 %.
• The whole-prostate ADCratio may circumvent variations of ADC metrics across centres.
KeywordsAdult Prostatic neoplasms/diagnostic imaging Diffusion magnetic resonance imaging/methods Retrospective studies Sensitivity and specificity
Apparent diffusion coefficient
Echo planar imaging
Intraclass correlation coefficient
Region of interest
Compliance with ethical standards
The scientific guarantor of this publication is François Cornud.
Conflict of interest
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.
Statistics and biometry
One of the authors has significant statistical expertise: firstname.lastname@example.org
Written informed consent was waived by the Institutional Review Board.
Institutional Review Board approval was waived by the ethics committee.
• case-control study
• multicentre study
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