Comparison of Stretched-Exponential and Monoexponential Model Diffusion-Weighted Imaging in Prostate Cancer and Normal Tissues

Background: To compare stretched-exponential and monoexponential model diffusion-weighted imaging (DWI) in prostate cancer and normal tissues. Methods: Twenty-seven patients with prostate cancer underwent DWI exam using b-values of 0, 500, 1000, and 2000 s/mm(2). The distributed diffusion coefficients (DDC) and alpha values of prostate cancer and normal tissues were obtained with stretched-exponential model and apparent diffusion coefficient (ADC) values using monoexponential model. The ADC, DDC (both in 10(-3) mm(2)/s), and alpha values (range, 0-1) were compared among different prostate tissues. The ADC and DDC were also compared and correlated in each tissue, and the standardized differences between DDC and ADC were compared among different tissues. Results: Data were obtained for 31 cancers, 36 normal peripheral zone (PZ) and 26 normal central gland (CG) tissues. The ADC (0.71 +/- 0.12), DDC (0.60 +/- 0.18), and alpha value (0.64 +/- 0.05) of tumor were all significantly lower than those of the normal PZ (1.41 +/- 0.22, 1.47 +/- 0.20, and 0.85 +/- 0.09) and CG (1.25 +/- 0.14, 1.32 +/- 0.13, and 0.82 +/- 0.06) (all P<0.05). ADC was significantly higher than DDC in cancer, but lower than DDC in the PZ and CG (all P<0.05). The ADC and DDC were strongly correlated (R-2 = 0.99, 0.98, 0.99, respectively, all P<0.05) in all the tissue, and standardized difference between ADC and DDC of cancer was slight but significantly higher than that in normal tissue. Conclusion: The stretched-exponential model DWI provides more parameters for distinguishing prostate cancer and normal tissue and reveals slight differences between DDC and ADC values.