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The radiological protection has the purpose of safeguarding the physical well-being of the user, preventing exposure to detrimental levels of ionizing radiation. This study introduces a novel, cost-effective category of lead-free elastomeric material designed for radiation shielding. The filler compounds utilized are notably lighter than conventional lead-based materials, enhancing user ergonomics during application. They comprise of a blend of barium sulfate combined or not with magnesium oxide with addition-cure liquid silicone rubber. To ensure the effectiveness of the radiation shielding, X-ray transmission measurements were performed for the different thicknesses of the materials and the results compared with Monte Carlo simulations. Additionally, the physical properties of the new materials, such as density, homogeneity, tensile strength, viscosity, and wettability, were also evaluated. The findings indicate that both materials fulfill the requirement for application in radiation protection garments.

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In Colombia, medical physics started formally about 3 decades ago. Two master's programs in medical physics initiated activities at two different universities. In particular, the master's program at the Pontificia Universidad Javeriana has been underway since 2012, and taking into account its projections, a team was established in 2015 in collaboration with the Universidad Distrital Francisco José de Caldas to conduct basic research on cancer treatment using neutron capture therapy (NCT). The primary goal of our initiative is to create the infrastructure required to adapt new technologies in our universities in the future. The long-term objective is to use neutron radiation to study not only NCT but also biomolecules, membranes, and materials. This will require the commissioning of an actual nuclear facility. Our group has been exclusively focused on carrying out calculations with GEANT4 because of its characteristics as open-source software, its accessibility, and its ample worldwide use and validation in the particle physics, nuclear physics, and medical physics communities. In this work, we present some results of our preliminary design for the ion accelerator column of a compact neutron generator. Also, we present the characterization of the kinematical and dose distributions of boron neutron capture processes using Geant4.

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A computational simulation of alpha-particle expansion, emitted by 222Rn naturally diluted in the water of a spring located in the state of Puebla Mexico, is presented. This simulation provided information on the volume of expansion of the alpha particles in the vicinity of the spring and thus awareness if there was a radiological risk for the users or the population that lived near to it. Before performing the simulation, several measurements were made to water samples with a dynamic measurement system. This in order to know the level of radon concentration and compare the results obtained with the levels recommended by the United States Environmental Protection Agency (US-EPA) and the World Health Organization (WHO). In addition, to know if there was a radiological risk due to the presence of gamma emitting radionuclides, complementary water analyses were carried out using gamma-ray spectrometry techniques. The simulation was developed using the scientific software of particle interaction with matter, Geant4. The different variables declared for the software parameters are presented in this document. The results of the radon measurements in the water and the computational simulation, determined that there was no radiological risk due to alpha radiation. Furthermore, the results from the gamma-ray spectrometer showed that there was no presence of other hazardous radionuclides in the water.

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The chemical stage of the Monte Carlo track-structure (MCTS) code Geant4-DNA was extended for its use in DNA strand break (SB) simulations and compared against published experimental data. Geant4-DNA simulations were performed using pUC19 plasmids (2686 base pairs) in a buffered solution of DMSO irradiated by60Co or137Csγ-rays. A comprehensive evaluation of SSB yields was performed considering DMSO, DNA concentration, dose and plasmid supercoiling. The latter was measured using the super helix density value used in a Brownian dynamics plasmid generation algorithm. The Geant4-DNA implementation of the independent reaction times method (IRT), developed to simulate the reaction kinetics of radiochemical species, allowed to score the fraction of supercoiled, relaxed and linearized plasmid fractions as a function of the absorbed dose. The percentage of the number of SB after •OH + DNA and H• + DNA reactions, referred as SSB efficiency, obtained using MCTS were 13.77% and 0.74% respectively. This is in reasonable agreement with published values of 12% and 0.8%. The SSB yields as a function of DMSO concentration, DNA concentration and super helix density recreated the expected published experimental behaviors within 5%, one standard deviation. The dose response of SSB and DSB yields agreed with published measurements within 5%, one standard deviation. We demonstrated that the developed extension of IRT in Geant4-DNA, facilitated the reproduction of experimental conditions. Furthermore, its calculations were strongly in agreement with experimental data. These two facts will facilitate the use of this extension in future radiobiological applications, aiding the study of DNA damage mechanisms with a high level of detail.

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PURPOSE: This study aims to use GATE/Geant4 simulation code to evaluate the performance of dose calculations with Anisotropic Analytical Algorithm (AAA) in the context of lung SBRT for complex treatments considering images of patients. METHODS: Four cases of non-small cell lung cancer treated with SBRT were selected for this study. Irradiation plans were created with AAA and recalculated end to end using Monte Carlo (MC) method maintaining field configurations identical to the original plans. Each treatment plan was evaluated in terms of PTV and organs at risk (OARs) using dose-volume histograms (DVH). Dosimetric parameters obtained from DVHs were used to compare AAA and MC. RESULTS: The comparison between the AAA and MC DVH using gamma analysis with the passing criteria of 3%/3% showed an average passing rate of more than 90% for the PTV structure and 97% for the OARs. Tightening the criteria to 2%/2% showed a reduction in the average passing rate of the PTV to 86%. The agreement between the AAA and MC dose calculations for PTV dosimetric parameters (V100; V90; Homogeneity index; maximum, minimum and mean dose; CIPaddick and D2cm) was within 18.4%. For OARs, the biggest differences were observed in the spinal cord and the great vessels. CONCLUSIONS: In general, we did not find significant differences between AAA and MC. The results indicate that AAA could be used in complex SBRT cases that involve a larger number of small treatment fields in the presence of tissue heterogeneities.

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The aim of this work was to calculate S values for 99mTc, 67Ga, 68Ga, 18F, 223Ra, 166Ho, 90Y, 161Tb 131I and 177Lu, using a mouse phantom (MOBY) standard and considering the anatomic sizes from males and females, the simulation of radiation transport was performed with GATE/Geant4 platform. This indicates that in the internal dosimetry the use of a customized geometry is relevant for each gender and a standard model is not a good choice.

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CeBr3 crystals meet many of the demands of high performance scintillators, due to their excellent timing properties, good effective Z and high photon yield. It is important to characterize their efficiency and to verify whether modern Monte Carlo codes are reliable enough to reproduced the observed values. We report here on the measurement of both total and photopeak efficiency of a 1" diameter×1" height CeBr3 crystal for gamma-ray energies up to 1.4MeV at several distances, using a variety of low energy gamma rays sources. The measured experimental efficiencies are compared with simulations developed in the framework of PENELOPE and GEANT4.

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Understanding the fundamental mechanisms involved in the induction of biological damage by ionizing radiation remains a major challenge of today's radiobiology research. The Monte Carlo simulation of physical, physicochemical and chemical processes involved may provide a powerful tool for the simulation of early damage induction. The Geant4-DNA extension of the general purpose Monte Carlo Geant4 simulation toolkit aims to provide the scientific community with an open source access platform for the mechanistic simulation of such early damage. This paper presents the most recent review of the Geant4-DNA extension, as available to Geant4 users since June 2015 (release 10.2 Beta). In particular, the review includes the description of new physical models for the description of electron elastic and inelastic interactions in liquid water, as well as new examples dedicated to the simulation of physicochemical and chemical stages of water radiolysis. Several implementations of geometrical models of biological targets are presented as well, and the list of Geant4-DNA examples is described.

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OBJETIVO: Este artigo apresenta a avaliação dosimétrica da radioterapia por íons de carbono em comparação à protonterapia. MATERIAIS E MÉTODOS: As simulações computacionais foram elaboradas no código Geant4 (GEometry ANd Tracking). Um modelo de olho discretizado em voxels implementado no sistema Siscodes (sistema computacional para dosimetria em radioterapia) foi empregado, em que perfis de dose em profundidade e curvas de isodose foram gerados e superpostos. Nas simulações com feixe de íons de carbono, distintos valores de energia do feixe foram adotados, enquanto nas simulações com feixe de prótons os dispositivos da linha de irradiação foram incluídos e diferentes espessuras do material absorvedor foram aplicadas. RESULTADOS: As saídas das simulações foram processadas e integradas ao Siscodes para gerar as distribuições espaciais de dose no modelo ocular, considerando alterações do posicionamento de entrada do feixe. Os percentuais de dose foram normalizados em função da dose máxima para um feixe em posição de entrada específica, energia da partícula incidente e número de íons de carbono e de prótons incidentes. CONCLUSÃO: Os benefícios descritos e os resultados apresentados contribuem para o desenvolvimento das aplicações clínicas e das pesquisas em radioterapia ocular por íons de carbono e prótons.

OBJECTIVE: The present paper addresses the dosimetric evaluation of carbon ion radiotherapy as compared with proton therapy. MATERIALS AND METHODS: Computer simulations were undertaken with the Geant4 (GEometry ANd Tracking) code. An eye model discretized into voxels and implemented in the Siscodes system (computer system for dosimetry in radiation therapy) was utilized to generate and superimpose depth dose profiles and isodose curves. Different values for beam energy were adopted in the simulations of carbon ion beams, while in the simulation with proton beams irradiation line devices were included with different absorbing material thicknesses. RESULTS: The simulations outputs were processed and integrated into the Siscodes to generate the spatial dose distribution in the eye model, considering changes in the beam entrance position. The dose rates were normalized as a function of the maximum dose for a beam at a specific entrance position, incident particle energy and number of incident carbon ions and protons. CONCLUSION: The described benefits together with the presented results contribute to the development of clinical applications and researches on carbon ion and proton therapy.

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OBJETIVO: Comparar dados de dosimetria e fluência de fótons entre diferentes modelos de mama, discutindo as aplicações em testes de constância e estudos dosimétricos aplicados à mamografia. MATERIAIS E MÉTODOS: Foram simulados diferentes modelos homogêneos e um modelo antropomórfico de mama tipo voxel, sendo contabilizadas: a dose total absorvida no modelo, a dose absorvida pelo tecido glandular/material equivalente, e a dose absorvida e a fluência de fótons em diferentes profundidades dos modelos. Uma câmara de ionização simulada coletou o kerma de entrada na pele. As combinações alvo-filtro estudadas foram Mo-30Mo e Mo-25Rh, para diferentes potenciais aceleradores de 26 kVp até 34 kVp. RESULTADOS: A dose glandular normalizada, comparada ao modelo voxel, resultou em diferenças entre -15 por cento até -21 por cento para RMI, -10 por cento para PhantomMama e 10 por cento para os modelos Barts e Keithley. A variação dos valores da camada semirredutora entre modelos foi geralmente inferior a 10 por cento para todos os volumes sensíveis. CONCLUSÃO: Para avaliar a dose glandular normalizada e a dose glandular, em mamas médias, recomenda-se o modelo de Dance. Os modelos homogêneos devem ser utilizados para realizar testes de constância em dosimetria, mas eles não são indicados para estimar a dosimetria em pacientes reais.

OBJECTIVE: To compare data regarding dosimetry and photons fluence in different breast phantoms, discussing constancy tests and dosimetry applied to mammography. MATERIALS AND METHODS: Different homogeneous breast phantoms and one anthropomorphic voxel phantom were developed for collection of data regarding total absorbed dose in the phantom, absorbed dose in the glandular tissue material-equivalent, absorbed dose and photons fluence at different depths in the phantoms. A simulated ionization chamber collected the entrance skin kerma. Target-filter combinations (Mo-30Mo and Mo-25Rh) were studied for different accelerating potentials of 26 kVp to 34 kVp. RESULTS: As compared with the voxel phantom, the normalized glandular dose resulted in differences from -15 percent to -21 percent for RMI, -10 percent for PhantomMama, and 10 percent for the Barts and Keithley models. The half-value layer variation was generally < 10 percent for all the sensitive volumes. CONCLUSION: The phantom proposed by Dance is recommended for evaluating the glandular dose and normalized glandular dose in a standard breast. Homogeneous phantoms should be utilized for constancy tests in dosimetry, but they are not appropriate for estimating dosimetry in actual patients.

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OBJETIVO: Propõe-se avaliar os perfis de dose em profundidade e as distribuições espaciais de dose para protocolos de radioterapia ocular por prótons, a partir de simulações computacionais em código nuclear e modelo de olho discretizado em voxels. MATERIAIS E MÉTODOS: As ferramentas computacionais empregadas foram o código Geant4 (GEometry ANd Tracking) Toolkit e o SISCODES (Sistema Computacional para Dosimetria em Radioterapia). O Geant4 é um pacote de software livre, utilizado para simular a passagem de partículas nucleares com carga elétrica através da matéria, pelo método de Monte Carlo. Foram executadas simulações computacionais reprodutivas de radioterapia por próton baseada em instalações pré-existentes. RESULTADOS: Os dados das simulações foram integrados ao modelo de olho através do código SISCODES, para geração das distribuições espaciais de doses. Perfis de dose em profundidade reproduzindo o pico de Bragg puro e modulado são apresentados. Importantes aspectos do planejamento radioterápico com prótons são abordados, como material absorvedor, modulação, dimensões do colimador, energia incidente do próton e produção de isodoses. CONCLUSÃO: Conclui-se que a terapia por prótons, quando adequadamente modulada e direcionada, pode reproduzir condições ideais de deposição de dose em neoplasias oculares.

OBJECTIVE: The present study proposes the evaluation of the depth-dose profiles and the spatial distribution of radiation dose for ocular proton beam radiotherapy protocols, based on computer simulations in nuclear codes and an eye model discretized into voxels. MATERIALS AND METHODS: The employed computational tools were Geant4 (GEometry ANd Tracking) Toolkit and SISCODES (Sistema Computacional para Dosimetria em Radioterapia - Computer System for Dosimetry in Radiotherapy). Geant4 is a toolkit for simulating the passage of particles through the matter, based on Monte Carlo method. Computer simulations of proton therapy were performed based on preexisting facilities. RESULTS: Simulation data were integrated into SISCODES on the eye's model generating spatial dose distributions. Dose depth profiles reproducing the pure and modulated Bragg peaks are presented. Relevant aspects of proton beam radiotherapy planning are considered such as material absorber, modulation, collimator dimensions, incident proton energy and isodose generation. CONCLUSION: The conclusion is that proton therapy when properly modulated and directed can reproduce the ideal conditions for the dose deposition in the treatment of ocular tumors.

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A Braquiterapia é uma etapa essencial do tratamento de vários tipos de câncer. O uso de fontes de 192Ir com alta taxa de dose impõe a necessidade de procedimentos apropriados de calibração e controle da qualidade, de forma a garantir a exatidão da dose administrada. Um programa em GEANT4 foi desenvolvido para calcular grandezas dosimétricas em um fantoma de acrílico. Assim foi possível definir uma metodologia para avaliar a dose na vizinhança de uma fonte de braquiterapia utilizando um formalismo em função da grandeza dose absorvida na água para dosimetria termoluminescente. Um fantoma de acrlílico foi proposto e caracterizado com grandezas do protocolo TG- 3 calculadas pelo método de Monte Carlo. O fantoma foi irradiado com os TLDs no equipamento de braquiterapia do Varian Gammamed Plus, a dose e o kerma de referência calculado concordaram em 0,30%.

High dose rate Brachytherapy is an essential part of the treatment of several types of cancer. The use of high dose rate 192Ir sources requires appropriate calibration in order to ensure the desired level of accuracy of the dose delivered. A GEANT4 program was developed to calculate dosimetric quantities in an acrylic phantom. Thus it was possible to define a methodology for calculating the dose around a brachytherapy source using a termoluminescent dosimetry formalism in terms of water absorbed dose. An acrylic phantom was proposed and characterized with magnitudes protocol TG-43 calculated by Monte Carlo method. The phantom was irradiated in Varian's brachytherapy equipment Gammamed Plus, the dose and the kerma calculated reference agreed at 0,30%.

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