Supervoltage beam films.

Abstract In order to determine the optimal technic for obtaining supervoltage beams films, electron emission measurements, phantom films and gradation studies were carried out with various films, metal foils and fluorescent screens. The best beam fihns were obtained with a combination of a regular diagnostic X-ray film sandwiched between two lead foils in a cassette, which provides good contact between film and lead foils. The back lead foil improves the contrast, while the front lead foil improves the sharpness of the beam film. The optimal foil thickness for the back lead foil is 0.1 mm for 60Co, 0.2 mm for 4 MV and 0.5 mm for 10 MV X-rays. The front lead foil should be twice as thick. The best films are obtained if the film is in contact with the body. Beam films taken with our combination required only about 1 10 of the radiation exposure of the commercially available “Localization film” and were far superior in contrast and sharpness.