Three-dimensional prostate ultrasound and its application to cryosurgery.

Transrectal ultrasound (TRUS), despite its undeniable utility in prostate imaging, employs a spatially flexible and variable 2-dimensional (2-D) imaging technique to visualize a 3-dimensional (3-D) disease process and anatomy. To circumvent some of the limitations of 2-D TRUS, 3-D TRUS was developed. The system consists of a motorized assembly (to hold a standard ultrasound transducer) and a computer with a video frame grabber. The microcomputer, using software developed in our laboratory, rapidly reconstructs a series of linear ultrasound images into a 3-D image. The 3-D TRUS technology has been incorporated into our program for cryoablation of the prostate. With intraoperative 3-D TRUS providing a unique coronal view, cryoprobe placement is facilitated to detect malalignment and avoid subsequent suboptimal cryoablation. In our use of 3-D TRUS guidance, in all 21 initial patients, probe malalignment, otherwise not apparent on standard 2-D TRUS, was detected and corrected before cryosurgery. With median follow-up of just < 1 year, only 2 of 44 biopsy cores (from the same site of 1 patient) were positive at 3 and 6 months. 3-D TRUS appears to be a valuable adjunctive tool in prostate imaging, especially in providing guidance for cryoblation of prostate cancer.