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In Brazil, concrete and cement are highly used in construction, therefore mixers are widely used in this industry. During the fabrication process of concrete/cement, the equipment may fail and compromise the appropriate mixing procedure. Besides that, it is also important to determine the right point of homogeneity of the mixture. It is important to have a methodology to monitor the mixing process to ensure the quality of the product. This study presents a methodology based on the principles of the radioactive particle tracking technique to predict the instantaneous positions occupied by the radioactive particle inside an industrial mixer by means of a mathematical location algorithm. The detection geometry modeled by means of MCNPX code employs an array of eight NaI(Tl) scintillator detectors, a 198Au spherical gamma-rays source with isotropic emission and a test section filled with concrete that represents an industrial mixer. The choice of the radionuclide is due its well-characterized peak of 411 keV, its half-life of 2.7 days and the possibility to obtain 198Au by neutron activation in reactors. The purpose of this study is to use an artificial neural network as a location algorithm of the 198Au radioactive particle inside an industrial mixer. Results showed that over 56% of the cases were below 5% of relative error for all coordinates of the radioactive particle, which indicates that it is possible to track the radioactive particle trajectory inside the industrial mixer using the artificial neural network algorithm. • Radioactive Particle Tracking methodology to evaluate concrete mixer. • Mathematical simulation developed using MCNPX code. • Geometry employs 198Au (411 keV) gamma-ray source and eight NaI(Tl) detectors. • An artificial neural network calculates the radioactive particle position. [ABSTRACT FROM AUTHOR]

This study discusses a computer simulation for the equivalent ambient dose due to photons, H*(10)p, and neutrons, H*(10)n, in the patient's plane undergoing radiation therapy. A standard radiotherapy room with an additional shielding made by one lead or steel tenth-value layer was considered. A Varian 2100/2300 C/D linear accelerator head operating at 18 MV was modeled. Jaw openings of 5 cm × 5 cm, 10 cm × 10 cm, 20 cm × 20 cm, and 30 cm × 30 cm, as well as the multileaf collimator under eight different angles of gantry inclination, were also modeled. The use of steel in the shield generates a slightly raised average value of H*(10)p (0.527%) compared to when using lead. This finding can be interpreted as that the use of lead or steel coating makes no difference to the additional shield calculations when only photons are considered. When considering the contribution to H*(10)n, there is a significant difference (11.7% increase) for using lead compared to steel shielding. • Simulation of H*(10)p on the patient plane allows assessing of additional shielding. • No difference for lead or steel additional shielding concerning photons. • Lead increases H*(10) in comparison to steel. [ABSTRACT FROM AUTHOR]

Medical linear accelerators (linacs) require a physical structure designed to provide adequate structural support which ensures the safety of patients, operators and the general public. During a radiotherapy session, healthy tissues are exposed to radiation, even with these safety guarantees. This unwanted exposure may increase the likelihood of developing secondary cancer. This work uses the MCNP-5 code to computationally simulate a conformational 3D radiotherapy protocol for prostate cancer. Also, it investigates the potential effects of radiotherapy room shielding composition on equivalent and effective doses in the patient's body. A computational model of an actual room was developed considering a Varian Trilogy linac operating at 10 MeV. This model enabled dose calculations for an anthropomorphic phantom called REX to be performed. This phantom has sufficient details of all relevant organs and tissues needed to estimate the effective dose of the patient. The treatment protocol modeled in this study came from the database of patients treated by the Brazilian National Cancer Institute (Inca). For this protocol, the total dose to be applied to the patient is equally distributed over the four gantry inclination angles (0°, 90°, 180° and 270°). The simulated results suggested that the equivalent dose on different organs and tissues has been increased by concrete shielding. Regarding the effective dose due to the presence of additional shielding (steel or lead), the simulation suggests that such variations can be considered small. Overall the results allowed quantifying the specific contribution of concrete, lead, and steel as part of shielding on the equivalent and effective doses in the patient. • The concrete shielding contributes to the increase of the patient's equivalent dose. • The contribution of 1 TVL of steel or lead in the primary belt would be irrelevant. • The dose portion attributed to shielding is approximately homogeneous outside the treatment region. • The equivalent dose for several organs/tissues is impacted by lead/steel shielding. [ABSTRACT FROM AUTHOR]