The goal of this program is to provide the nuclear medicine community with a compact linear accelerator (linac) for the production of the principal short-lived radioisotopes, which are of great interest in positron emission tomography (PET) imaging and functional studies.Phase II will result in the fabrication and assembly of a prototype PET linac according to the design specifications from the Phase I study. The resulting proton linac will be only 4.8 meters long, weigh 3,000 pounds, use only 25 kW of input power, require only minimal shielding, and have a production cost of about $760,000. It will require only 250 square feet of floor space with shielding, be operated remotely from a small console, and be easy to maintain and operate, as well as reliable and rugged.The prototype will be installed in a functioning nuclear medicine department. The necessary radioisotope production targets will be developed in cooperation with that medical center. Phase II will be completed with the acceptance of the prototype by the center as a working radioisotope production accelerator.National Cancer Institute (NCI)