Beginning in 1987, high-intensity focused ultrasound was investigated experimentally in a canine model to determine whether or not prostate tissue could be destroyed with good aiming and control. Subsequently a transrectal probe was developed and used to treat canine prostates in a formal study to determine whether or not this technology could be used to treat human benign prostatic hypertrophy. Next, after FDA approval, 15 patients were treated at Indiana University in the fall of 1992. Both canine and human studies have shown that high-intensity focused ultrasound administered via a transrectal probe is capable of creating prostate lesions without injury to intervening and surrounding tissue.