Quantitative assessment of prostate cancer using an individualized apparent diffusion coefficient intensity scale: a proposal.

In this retrospective study, the diagnostic performance of an individualized apparent diffusion coefficient (ADC) signal intensity (SI) scale for differentiating prostate cancer (PCa) from benign simplified Prostate Imaging Reporting and Data System (S-PI-RADS) 4 lesions detected on biparametric magnetic resonance imaging (bpMRI) was evaluated. A total of 102 patients with biopsy-confirmed PCa and 79 patients with benign lesions (inflammation, HGPIN, ASAP) presenting as S-PI-RADS 4 were included. An individualized ADC SI scale was generated for each patient using maximum and minimum ADC values from the bladder and femoral head, respectively. The midpoint (ADC_mean) and the percentage difference (PD) between ADC_mean and lesion intensity (ADC_lesion) were calculated. Differences and diagnostic performance were assessed using Mann-Whitney U tests and receiver operating characteristic (ROC) analysis. PCa lesions demonstrated significantly lower ADC values and higher PDs compared with benign lesions (P<0.001). ROC analysis of PD yielded an area under the curve (AUC) of 0.798. Using a PD cut-off of 14.67%, sensitivity and specificity for detecting PCa were 73.5% and 94.9%, respectively. Intra-reader repeatability was high [intraclass correlation coefficient (ICC) 0.92-0.94], and PD values remained robust across variations in ADC fitting. The individualized ADC SI scale provides a patient-specific quantitative measure that effectively distinguishes malignant from benign S-PI-RADS 4 lesions. This approach complements visual bpMRI assessment, demonstrates high specificity, and has the potential to reduce unnecessary biopsies. Further prospective studies are warranted to validate its clinical utility.