Dose distribution in healthy tissues by computer modeling of the Alderson Rando phantom in Monte Carlo method

According to the World Health Organization (Who), cancer is one of the leading causes of mortality in the world. Despite of efficiency of radiotherapy, errors in plan or procedure can influence in the quality, allowing serious consequences for the patient. Among the factors that influence the quality of radiotherapy, on predominates the inaccuracy of dose calculation by the planning system, since overdose or under dose are harmful to the patient. Therefore, new methodologies that minimize the inaccuracy in the calculation of the dose to be administered are required. The aim of the present work is to analyze the photon absorbed dose deposited in healthy organs and tissues submitted to teletherapy treatment, through computer simulation using the radiation transport code MCNP6. For this purpose, a radiotherapy treatment was simulated using the Siemens Oncor Expression linear accelerator for irradiation on two gantry rotations (0, 45 and 180 degrees) with an opening field 10 x 10 cm, the computational modeling the patient body was performed using the Alderson Rando male phantom in voxel, all structures inserted inside the radiotherapy room were also simulated. The absorbed doses were obtained by F5 command used as point dosimeter (similar to TLD-100). The dosimeters are arranged in the Alderson Rando in 3 cm x 3 cm matrix. The TLDs were distributed in 7 slices, all comprised in the Alderson Rando thorax region, simulating absorbed dose due to photons in left lung and tissues. The highest dose rate was found in TLD number 16, located in slice 12 in the left lung, presenting a dose of 0.9452/Gy situated within the primary field of incidence of the beam. (Author)