Visualization of peri-prostatic neurovascular fibers before and after radical prostatectomy by means of diffusion tensor imaging (DTI) with clinical correlations: preliminary report

To evaluate if diffusion tensor imaging (DTI) is able to detect morphological changes of peri-prostatic neurovascular fibers (PNF) before and after robot-assisted radical prostatectomy (RARP) and if these changes are related to urinary incontinence (UI) and erectile dysfunction (ED). From October 2014 and August 2017, 26 patients with biopsy-proven prostate cancer underwent prostatic multiparametric magnetic resonance imaging (mp-MRI) including DTI sequencing before, and 6 months after, RARP. Images were analyzed by placing six regions of interest (ROI), respectively, at base, mid gland, and apex, one for each side, to obtain tractographic reconstruction of the PNF. Patients were asked to complete International Consultation Incontinence Questionnaire-Short Form (ICIQ-SF) and International Index of Erectile Function (IIEF-5) questionnaires before RARP and 6 months post-operatively. Fractional anisotropy (FA), number (N), and length (L) of PNF before and after RARP were compared by means of Student's t test; Spearman's test was used to evaluate correlation between DTI parameters and questionnaires' scores. We observed a significant difference in N values before and after RARP (p < 0.001) and a negative correlation between IIEF-5 score and post-operative FA values at both the right (rho = - 0.42; p = 0.0456) and left (rho = - 0.66; p = 0.0006) base of the prostate. DTI with tractography of PNF is able to detect quantitative changes in N, L, and FA values in PNF after RARP. In particular, we observed an inverse correlation between FA of PNF and ED at 6 months after RARP. Further investigations are needed to confirm this trend.