American surgeon who pioneered the practice of cryosurgery (destroying tissues by freezing them) in the removal of brain tumors. Although variations of cryosurgery had been attempted for more than 100 years, Cooper's method, using liquid nitrogen, was the first to work well with internal tissues. Cryosurgery is now used to remove skin lesions (such as warts), skin tumors, gynecologic tumors, ophthalmic lens removals, and other procedures. It is considered to be safe and reliable in both the operating room and in a family doctor's office.