METHOD FOR CONSTRUCTING PHOTON SOURCE MODEL FUNCTION OF MEDICAL LINEAR ACCELERATOR

A method for constructing a photon source model function of a medical linear accelerator, for calculating the dose of rays in a radiation therapy scheme is disclosed. A source model of a therapeutic photon beam of the accelerator includes a primary ray photon source model and a scattered ray photon source model. Physical parameters in the two parts of source model functions include the position coordinates of an emission point of a particle, a projection value of a unit momentum vector in a three-dimensional orthogonal direction, and the energy of the particle. By utilizing the model functions, photon fluence information, energy spectrum information, and unit momentum direction information of photons on any phase space plane can be accurately calculated. The method and thought for constructing the source model are applicable to construction of source models of photon beams with various nominal energies of the accelerator used in a radiation therapy.