The effect of collimator backscatter radiation on photon output of linear accelerators

摘要: The field‐size dependence of the photon output linear accelerators in air has been attributed part to changes amount radiation backscattered from collimator jaws into dose monitor chamber. This possible effect was investigated for a variety with energies 4 15 MV by measuring unit rate (MU/min) different openings. measurement made without feedback control, i.e., constant electron beam current accelerator. independent setting all machines tested. Hence, it is concluded that chamber does not contribute variation field size.