Recently, an attempt has been made to use a transrectal ultrasound (TRUS) imaging to delineate the anatomy of the prostate gland and NVB during laparoscopic radical prostatectomy. However, it is difficult to obtain a steady image of TRUS with an operator. The investigators plan to perform a feasibility study to obtain TRUS imaging of the prostate and NVB during robot-assisted laparoscopic radical prostatectomy (RALRP). The investigators plan to use a robot-assisted TRUS probe holder to gently manipulate the probe to obtain steady TRUS images that may aid in visualization and dissection of the NVB during RALRP.