عنوان مقاله [English]
In the treatment of the tumors using proton therapy, the synchrotron emits a monoenergetic beam that transports most of its energy in a special position after entering the target. There are two approaches to invading the entire tumor tissue. One of these methods, which the present work deals with, is known as passive scattering. The proton beam should be passed through a rotating scatterer, called modulation wheel, to cover the total volume of the tumor. This scattering device, in its turning, places different thicknesses of materials on the path of the proton and converts this monoenergetic beam to a spectrum with lower energy. This beam is absorbed in the lower depth of the tissue. The goal of this approach is to achieve an energy absorption curve with a maximum flat area in the tumor volume and a fast reduction to zero after passing through the tumor. Investigating the effect of materials and the geometric changes of the dispersive components in the path of the proton beam is a significant issue affecting the shape of the absorption curve. Using the Geant4 toolkit which is based on the Monte Carlo method, this dispersive system was simulated. The calculation of the geometric characteristics of the range modulator wheel, which leads to a flattened absorption curve in the tumor area, has been studied in the literature. In the present work, a Python program with an iterative algorithm has been written to design an acceptable plane curve.