US Patent 7515681 High resolution proton beam monitor

A method and apparatus for monitoring a scanning beam of penetrating radiation, such as a scanning proton beam used to irradiate tissue. The position of the beam is tracked in real time by interposing a scintillator film between a source and an object of irradiation. An imaging detector, in optical communication with the scintillator, provides an output that is indicative of the position of the radiation and its variation with time. The accumulated dose over a scan may also be monitored.