A prospective comparison of the diagnostic performance of a high b-value diffusion-weighted image-guided score versus PI-RADS v2.1 for transition zone prostate cancer

Objective: The objective of this study is to evaluate the diagnostic accuracy of transition zone (TZ) scoring guided by diffusion-weighted imaging (DWI) with different b-values versus TZ lesion scoring under the current PI-RADS v2.1 standard for diagnosing transition zone prostate cancer (TZPCa). Methods: This prospective study enrolled 345 men with suspected prostate cancer (PCa). Following standardized multi-parametric magnetic resonance imaging (mpMRI), all patients underwent cognitive fusion-guided targeted biopsy and systematic biopsy, ultimately enrolling 50 patients with TZPCa and 121 patients with benign prostatic hyperplasia (BPH). DWI sequences were acquired with b-values of 50, 800, 1500, 2500, and 3000 s/mm². Three contrast groups were established for comparison with conventional PI-RADS v2.1 TZ scoring: DWI-TZ group: b=50, 800, 1500 s/mm²; h-DWI-TZ group: b=50, 800, 2500 s/mm²; uh-DWI-TZ group: b=50, 800, 3000 s/mm². Scoring procedure: Each radiologist first scored TZ lesions using standard b-values (50, 800, 1500) according to PI-RADS v2.1 criteria. After a 4-week interval, DWI-guided TZ scoring was performed on images from the three distinct b-value groups. The procedure for each group was identical: first, identify suspicious lesions on DWI/ADC images; then correlate these with T2WI images; finally, score TZ lesions according to PI-RADS v2.1 criteria. All scoring was performed independently by two radiologists. Results: When PI-RADS ≥ 3 was employed as the positive criterion, both the high b-value (h-DWI-TZ) and ultra-high b-value (uh-DWI-TZ) sequences exhibited significantly higher diagnostic sensitivity (0.855 and 0.823, respectively) and specificity (both 0.863) in comparison to conventional DWI sequences (sensitivity 0.677, specificity 0.630; p < 0.05 for both). Conversely, the standard high b-value (DWI-TZ) sequence demonstrated no statistically significant difference from the conventional sequence. When the threshold was elevated to PI-RADS score ≥4, the h-DWI-TZ sequence exhibited significantly superior specificity (0.967 vs. 0.874) and positive predictive value (PPV, 0.902 vs. 0.630) in comparison to the conventional sequence (both p<0.001). In addition, the h-DWI-TZ sequence exhibited markedly superior interobserver agreement (κ-value: 0.689 vs. 0.272, p<0.001). Conclusions: Diffusion-weighted imaging with high and ultra-high b-values guided TZ scoring enhances diagnostic accuracy for TZPCa.