محاسبه میزان دز پرتوهای ترمزی ناشی از الکترون ها در پرتو درمانی با الکترون در بیمارستان آیت ا...خوانساری اراک

During the radiation therapy with electron beam, due to electron interaction and scattering from structures of the head of the medical linear accelerator, unwanted photons are produced. The main contribution of the photon contamination is resulted from the various components of the medical linear accelerator on the way of the high energy electron beam, and few percent is due to the interaction of the beam with the phantom or the patient's body. Structure and material of the head of the medical linear accelerator have effective roles on production of x-rays dose from the electrons beam. Therefore, the parameters of electron beam produced by a linear accelerator manufactured by different companies were varied. This difference may be seen even among the accelerators produced by one company. Therefore, this parameter must be described separately for each machine. In order to measure photon contamination at the electron mode of the Elekta Precise linear accelerator, thermoluminescence detectors (TLD700 & GR200) at two energies (10 & 15MeV) in polyethylene phantom were applied. These data were compared with the calculations using MCNPX code. Our results show an appropriate match between theory and experimental data at both energies. It shows that the rate of produced bremsstrahlung photons dose for tallies that are close to the phantom are in mSv range. Then it will be possible to calculate bremsstrahlung photon dose for different point of radiotherapy room of the Ayat-O-lah Khansari hospital by the Monte Carlo codes.