Role of the Apparent Diffusion Coefficient (ADC) values analysis in Diffusion Weighted Imaging (DWI-MR) in the characterization of prostatic disease on Multiparametric Magnetic Resonance Imaging (Mp-MRI) of the prostate.

Purpose To evaluate if apparent diffusion coefficient analysis on magnetic resonance imaging can differentiate between normal and pathological prostate tissue, including prostate cancer and precancerous conditions (ASAP and PIN). Materials and Methods Prostate MRI with endorectal coil was performed in 93 patients (mean age 65.4). Regions of interest were placed over suspicious areas, detected on MRI, and over areas with normal appearance, and ADC values were recorded. Statistical differences between ADC values of suspicious and normal areas were evaluated. Histopathological diagnosis, obtained from targeted biopsy in 51 patients and from prostatectomy in 42 patients, were correlated to ADC values. Results Histopathological diagnosis revealed 58 cases of prostate cancer (PCa), 16 of high-grade prostatic intraepithelial neoplasia (HG-PIN), 10 of atypical small acinar proliferation (ASAP) and 12 histologic alterations after radiotherapy. Significant statistical differences between mean ADC values of normal prostate tissue versus PCa (p<.01), HG-PIN (p<.01), ASAP (p<.05) and post-radiotherapy changes (p<.05) were found. Significant differences were observed between mean ADC values of PCa versus HG-PIN (p<.05) and ASAP (p<.01) with many overlapping values. Differences between mean ADC values of HG-PIN versus ASAP (p=0.17) and between post-radiotherapy alterations versus PCa (p=0.24), HG-PIN (p=0.76) and ASAP (p=0.69) were not significant. Conclusions The apparent diffusion coefficient analysis on DW-MRI allows a robust differentiation between normal prostate tissue and pathological conditions as PCa, ASAP and PIN. The discrimination of different pathological conditions within the intrapathological group and in post-radiotherapy fibrosis patients using apparent diffusion coefficient analysis, suffers of an excessive overlapping of the ADC values even if stastically significant differences have been reported.