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 b=2000 smm(-2). Methods: Diffusion-weighted imaging (DWIs) for 31 patients with PCa (65.2 +/- 7.1 years) were obtained pre-operatively at different b-values (0, 100, 500, 1000 and 2000 s mm(-2)) on a 3-T MRI. cDWIs at b=2000 were generated by using six b-value combinations: 0-100 s mm(-2) (cDWI(0-100)); 0-500 smm(-2) (cDWI(0-500)); 100-500 s mm(-2) (cDWI(100-500)); 0-1000 s mm(-2) (cDWI(0-1000)); 100-1000 s mm(-2) (cDWI(100-1000)); and 500-1000 s mm(-2) (cDWI(500-1000)). These cDWIs and measured DWIs with b=2000 s mm(-2) (mDWI(2000)) 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 mDWI(2000) (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; mDWI(2000), 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 >= 500 s mm(-2), as well as b=0 and b=1000 s mm(-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.