STOCKHOLM, Sweden--(BUSINESS WIRE)--One of the U.S. premier providers of Gamma Knife® surgery, The University of Pittsburgh Medical Center-Presbyterian (UPMC) in Pittsburgh, has agreed to purchase the new Leksell Gamma Knife® Perfexion™, the most advanced system ever for non-invasive radiosurgery of brain disorders. UPMC will be one of the first medical centers in the country to install this new system in the early spring of 2007. The UPMC order was booked by Elekta in November.