Contamination of an Alcyon Co-60 gamma rays by Electrons / 대한치료방사선과학회지

The Alcyon Co-60 gamma rays was studied for electron contamination. The surface dose, attributable almost entirely to contamination electrons, has a linear dependence on field width for square fields and an inverse square dependence on distance from the bottom of the fixed head assembly. Build-up and surface dose measurements were taken with and without an acrylic blocking tray in place. Further measurements were made with a copper filter designed to reduce secondary electrons emitted by photon interactions with the acrylic tray. The results are discussed in relation to skin sparing effect for radiation therapy patients. And to achieve the maximum skin sparing effect, the selection of the optimum SSD and TSD is needed.