Verification and evaluation of radiation-beam parameters of high-energy linear accelerator with gantry rotation

The radiation beam from a linear accelerator originates from the acceleration of the electrons in the accelerating structure. As the gantry rotates together with the accelerating structure, it is at different orientations with respect to the magnetic field of Earth. The deviations in the path of the electron beam due to the changes in the magnetic fields are corrected by steering coils surrounding the accelerating structure. In the present investigation, all deviations in photon and electron beam parameters of a high energy linear accelerator with gantry rotation are checked. The central axis dose is measured using a parallel-plate ionization chamber placed in the fabricated phantom via parallel-plate chamber holder. To measure the beam flatness and symmetry, a dosimetric plate designed to hold a radiosensitive film is used. The evaluation performed using the fabricated phantom confirms the accuracy of the dose delivered to patients at various gantry angles.