Computed diffusion-weighted MRI for prostate cancer detection: The influence of the combinations of b-values

Objective: To evaluate the influence of the combinations of b-values on computed diffusion-weighted images (cDWIs) for prostate cancer (PCa) detection at b52000smm^-2. Methods: Diffusion-weighted imaging (DWIs) for 31 patients with PCa (65.26 ±7.1 years) were obtained pre-operatively at different b-values (0, 100, 500, 1000 and 2000 smm^-2) on a 3-T MRI. cDWIs at b52000 were generated by using six b-value combinations: 0-100 smm^-2 (cDWI_0-100); 0-500 smm^-2 (cDWI_0-500); 100-500smm^-2 (cDWI_100-500); 0-1000smm^-2 (cDWI_0-1000); 100-1000smm^-2 (cDWI_100-1000); and 500-1000smm^-2 (cDWI_500-1000). These cDWIs and measured DWIs with b52000smm^-2 (mDWI₂₀₀₀) were evaluated in this setting. To assess image quality for each DWI, contrast ratios (CRs) of cancerous and non-cancerous lesions were evaluated. To compare the detectability of PCa for each DWI, receiver operating characteristic analysis was used. Results: CRs of all cDWIs were significantly higher than those of mDWI₂₀₀₀ (p <0.05). Areas under the curve of cDWI_0-100 (0.62) and cDWI_0-500 (0.65) were significantly smaller (p<0.05) than those of others (cDWI_100-500, 0.72; cDWI_0-1000, 0.73; cDWI_100-1000, 0.71; cDWI_500-1000, 0.74;mDWI₂₀₀₀, 0.72). Conclusion: The combinations of b-values influenced image quality and diagnostic ability of cDWIs for PCa detection. The combinations of b$100 and b$500smm^-2, as well as b50 and b51000smm^-2, were optimal in this study. Advances in knowledge: For generating the useful cDWI for PCa detection, radiologists should take care of the combination of b-values when including low b-values.