Background: Minimum apparent diffusion coefficient (ADC) values are independent predictors of clinically significant prostate cancer (csPC). We developed a novel ADC-based bi-color map and evaluated its utility for identifying lesions suspicious for csPC. Methods: We retrospectively analyzed 108 targeted prostate biopsy cases and 93 radical prostatectomy cases. In the biopsy cohort, we assessed the association between ADC-based bi-color map positivity and csPC in lesions with a Prostate Imaging–Reporting and Data System (PI-RADS) score ≥ 3. In the prostatectomy cohort, we evaluated additional color map-positive lesions not categorized as PI-RADS ≥ 3 on preoperative MRI. Results: In the biopsy cohort, 118 lesions were positive on the ADC-based bi-color map, including lesions outside PI-RADS ≥ 3 categories. Among 157 lesions with a PI-RADS score ≥ 3, csPC was detected in 65 lesions (41.4%). Of these lesions, 70 (44.6%) were positive on the bi-color map, and csPC was identified in 49 (70.0%). The added value of the bi-color map was most evident in PI-RADS 4 lesions, where csPC detection rates were significantly higher in color map-positive than in color map-negative lesions (74.4% vs. 23.3%). In the prostatectomy cohort, 215 lesions were positive on the bi-color map, and csPC was confirmed pathologically in 126 lesions (58.6%). Among 82 color map-positive lesions not classified as PI-RADS ≥3, 55 (67.1%) corresponded to csPC. Conclusions: The ADC-based bi-color map may improve lesion highlighting and risk stratification for csPC and help identify suspicious lesions overlooked on conventional MRI assessment.
Okada et al. (Mon,) studied this question.