LAUSR

ABSTRACT Radiodiagnosis and radiation treatment, in each of their areas such as imaging, radiotherapy and nuclear medicine, require precise calculations about the energy deposited and scattering of the ionizing radiation used. In healthcare applications, it is required to know the penetration and amount of energy deposited in the biological tissue irradiated by ionizing photons; these parameters are function of the photon interaction processes with matter, which can be analyzed experimentally or by Monte Carlo simulation. Purpose: The aim of this work was to develop a new Monte Carlo code for ionizing photon transport in water with the track structure technique, that allows to discriminate primary and secondary photons, and to determine the energy deposited, interaction coordinates, path length and time of flight (TOF) inside of scatter volume. Methods: C++ programming language was used. In the Compton scattering, the polar angle was sampled by methods: Kahn and EGS. Water spheres centered at the origin with different radius were used, where the isotropic point source was placed at (0, 0, 0) for different energies to compute the energy lost by photons and TOF inside spherical volume. Results: It was determined that the best sampling method for the polar angle generation in each Compton interaction was the EGS method. Energy deposited in target region filled with water was compared with MCNPX 2.6 and others’ results from literature. Mean TOF and pathlength inside region of interest was obtained for 4 radii and 5 energies. Conclusions: Quantities computed with the new code are, according to reported data, and so, the new code is reliable for photon transport in water using the track structure method; this will allow the new code to become a useful tool in the areas of radiology and radiation dosimetry. Also, TOF inside scatter volume was reported.