[Electron and low-energy photon contamination of the radiation beam from a Theratron 780 cobalt unit]

While high-energy photon radiation in radiotherapy of deeper tissues has a skin-sparing effect, contamination with electron and low-energy photon radiation can diminish and even abolish this effect. Experiments with perspex, aluminium and copper filters showed that a copper filter effectively diminished the skin dose owing to contaminated radiation.