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 = 2000s mm-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 2000smm-2) on a 3-T MRI. cDWIs at b = 2000 were generated by using six b-value combinations: 0-100 s mm-2 (cDWI0-100); 0-500 s mm-2 (cDWI0-500); 100-500s mm-2 (cDWI100-500);0-1000s mm2 (cDWI-0-1000); 100-1000smm-2 (cDWI100-500)1 and 500-1000 s mm2 (cDWI500-1000). These cDWIs and measured DWIs with b = 2000 s mm-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 cDWI0-0-100 (0.62) and cDWI0-500 (0.65) were significantly smaller (P < 0.05) than those of others (cDWI100-500 0.72; cDWI0-1000, 0.73; cDWI100-1000. 0.71; cDWI500-1000. 0.74; mDWI2000. 0.72). Conclusion: The combinations of b-values influenced imago 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 = 1000s 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. [ABSTRACT FROM AUTHOR]
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