Differentiation of prostate cancer and prostatitis in the peripheral zone with diffusion-weighted imaging: ADC value versus normalized ADC value

Purpose: The purpose of this study is to compare the diagnostic accuracy of prostate apparent diffusion coefficient (ADC) versus normalized prostate ADC using the normal peripheral zone as the reference site for the differentiation of prostate cancer and prostatitis in the peripheral zone. Methods: Fifty-two patients, 32 with prostate cancer and 19 with prostatitis, were assessed with single-shot echo-planar diffusion-weighted imaging using b values of 0 and 1000 s/mm2. Prostate ADC and normalized prostate ADC (defined as the ratio of lesion ADC to normal peripheral zone ADC) were compared between prostate cancer and prostatitis in the peripheral zone. Receiver operating characteristic (ROC) analysis was used to determine the performance of ADC and normalized prostate ADC for differentiation of prostate cancer and prostatitis in the peripheral zone. Results: There were significant differences in ADC and nADC between prostate cancer and prostatitis in the peripheral zone. ROC analysis showed no significant differences between ADC and nADC for differentiation of prostate cancer and prostatitis in the peripheral zone (area under the ROC curve, 0.935 vs. 0.926; P=0.843). Conclusions: Our results suggest that nADC with normal peripheral zone as the reference site had similar performance to ADC for the differentiation of prostate cancer and prostatitis in the peripheral zone when using diffusion-weighted imaging.