Monitor chamber backscatter for intensity modulated radiation therapy using multileaf collimators

摘要: Backscattered radiation into the machine monitor chamber can affect output variation, with changes in field size and shape. For intensity modulated therapy (IMRT) where many fields, which may have small dimensions, are summed to give an field, magnitude of backscatter will be different due both backscattering surface area changing, delivered units being larger than for equivalent static field. The effect variation a Philips SL15 accelerator has been investigated at 8 MV IMRT fields standard clinical operating condition anti-backscatter plate is fitted, also case removed. results show that absence between 4 cm by 40 backscattered was 5% fields. reduced this less 1%. When operated mode, place, additional were 0.3%. With removed, outputs lower, indicating presence radiation. It concluded MLC SL its plate, effects ignored