Synthetic diffusion-weighted imaging in prostate cancer diagnosis: a comparison study with different B-value combinations.

Aim: To evaluate the impact of different b-value combinations on synthetic diffusion-weighted imaging (sDWI) and determine the sDWI with an optimal b-value combination for prostatic cancer (PCa) diagnosis.

Material and methods: A retrospective analysis of 68 patients with abnormal prostate-specific antigen (PSA) was conducted. The sDWI images with b value of 1500 s/mm² were separately reconstructed by the following five b-value combinations: b=0, 200s/mm² (sDWI_0-200); b=600, 800s/mm² (sDWI_600-800); b=0, 600s/mm² (sDWI_0-600); b=200, 800s/mm² sDWI_200-800); b=0, 800s/mm² (sDWI_0-800). Quantitative analysis was performed on the acquired DWI (aDWI) images with b=1500s/mm² (aDWI₁₅₀₀) and all sDWI images. These six image groups were scored in five aspects for image quality and further reviewed by two radiologists via six protocols: Protocol Ⅰ, T₂WI+sDWI_0-200; Protocol Ⅱ, T₂WI+sDWI_600-800; Protocol Ⅲ, T₂WI+sDWI_0-600; Protocol Ⅳ, T₂WI+sDWI_200-800; Protocol Ⅴ, T₂WI+sDWI_0-800; Protocol Ⅵ, T₂WI+aDWI₁₅₀₀. The corresponding diagnostic efficacies for PCa were evaluated using receiver operating characteristic (ROC) curves.

Results: Contrast ratio values of all sDWI images were higher than those of aDWI₁₅₀₀ images. Contrast-to-noise ratio values of sDWI_0-200 and sDWI_600-800 images were lower than those of the rest sDWI images. All subjective quality scores of sDWI_0-600, sDWI_200-800, and sDWI_0-800 were significantly higher than other groups except for background signal suppression. The area under the curve (AUC) of Protocol Ⅲ, Ⅳ, Ⅴ, and Ⅵ was significantly larger than those of other protocols.

Conclusion: Different b-value combinations impact the image quality and diagnostic accuracy of sDWI for PCa detection. The combination of b≤200s/mm² and b≥600s/mm² revealed to be optimal.