The long-term objective of this program is the development of the capability of precision proton radiography with accelerator systems designed or used for proton radiation therapy. A proton radiograph taken immediately prior to radiation treatment could give increased confidence in the adequacy of the treatment plan, check alignment with tumor site, and confirm readiness and calibration of the entire system. For this result raster scanning of a very high quality proton beam is required, and the implementation has the potential of improving the effectiveness of radiation treatment of cancer by protons. Its use for diagnostic purposes independent of therapy could be justified in some instances. The specific aims of Phase I would be to demonstrate on a 200 MeV proton beam using ACCTEK's raster scanning system the practical feasibility of proton radiography and to evaluate its potential, as well as computed tomography, as an adjunct to proton therapy and for independent diagnostic purposes. Phase II would develop and test commercial systems including detectors and computer analysis programs. Phase III, funded privately would provide the equipment and techniques to implement this capability at any of the proton therapy facilities under construction or to be constructed.