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This chapter presents a specific reliability study of some GEANT4-DNA (version 10.02.p01) processes and models for proton transportation considering ultra-thin layers (UTL). The Monte Carlo radiation transport validation is fundamental to guarantee the simulation results accuracy. However, sometimes this is impossible due to the lack of experimental data and, it is then that the reliability evaluation takes an important role. Geant4-DNA runs in an energy range that makes impossible, nowadays, to perform a proper microscopic validation (cross-sections and dynamic diffusion parameters) and allows very limited macroscopic reliability. The chemical damage cross-sections reliability (experiment versus simulation) is a way to verify the consistency of the simulation results which is presented for 2 MeV incident protons beam on PMMA and PVC UTL. A comparison among different Geant4-DNA physics lists for incident protons beams from 2 to 20 MeV, interacting with homogeneous water UTL (2 to 200 nm) was performed. This comparison was evaluated for standard and five other optional physics lists considering radial and depth profiles of deposited energy as well as number of interactions and stopping power of the incident particle.

In geology field, the experimental or computational simulation of the sediment deposition process is widely used to characterize regions and possible findings. Noninvasive methods are the best way to evaluate sediments; in order of not to destroy the information of the sediment deposition structure. The use of computed tomography (CT) techniques to get images of sediments will be evaluated. A CT will be analyzed has a two stage process, the scan of body test to produce a set of X-ray images and the reconstruction step where the set of X-ray images is processed by computational algorithm to generate cross-sectional images of the scanned object. To test the method the X-ray images are generated using the Monte Carlo method with a XRMC tool, and the simulated images are 3D reconstructed using the Feldkamp, David e Kress algorithm. The reconstruction planes and the volume generated in the simulation showed very similar after a visual comparison for all of tested volumes. However a statistical analysis showed that there was no statistical coincidence of the simulated dimensions and reconstruction. The results presented showed the possibility to use CT to study the sediments in tanks or rivers.

The aim of this work is to simulate transmission data for different beam geometry and material composition in order to evaluate the effect of these parameters on transmission curves. The simulations are focused on outgoing spectra for shielding barriers used in PET facilities. The behavior of the transmission was evaluated as a function of the shielding material composition and thickness using Geant4 Monte Carlo code, version 9.2 p 03.The application was benchmarked for barited mortar and compared to The American Association of Physicists in Medicine (AAPM) data for lead. Their influence on the transmission curves as well the study of the influence of the shielding material composition and beam geometry on the outgoing spectra were performed. Characteristics of transmitted spectra, such as shape, average energy and Half-Value Layer (HVL), were also evaluated. The Geant4 toolkit benchmark for the energy resulting from the positron annihilation phenomena and its application in transmission curves description shown good agreement between data published by American Association on Physicists in Medicine task group 108 and experimental data published by Brasil. The transmission properties for different material compositions were also studied and have shown low dependency with the considered thicknesses. The broad and narrow beams configuration presented significant differences on the result. The fitting parameter for determining the transmission curves equations, according to Archer model is presented for different material. As conclusion were defined that beam geometry has significant influence and the composition has low influence on transmission curves for shielding design for the range of energy applied to PET.

Half Value Layer (HVL) test is an important technical information in conventional radiology once it is the only test which allows us to quantify beam quality in a complete way. This work promotes a preliminary analysis of the impact of aluminum alloy composition in the determination of HVL value taking into account a realistic geometry. Deterministic calculations and Monte Carlo Method were applied in order to make the proposed analysis. Six aluminum alloys (99% pure) commercialized and pure aluminum were used as comparative basis for both methods. Experimental data were collected in conventional radiology, using tungsten target and aluminum filter for two peak tensions (66 kVp, 81 kVp), and in mammography, using three target filter combinations( molybdenum-molybdenum, molybdenum-rhodium, tungsten-rhodium) for three peak tensions (25 kVp, 30 kVp and 35 kVp). Spectra used in the deterministic calculations were taken from Report No 78 of Institute of Physics and Engineering in Medicine, 1997. Results show that Mammography is more sensitive than conventional X-ray equipment to impurities in aluminum alloys (up to 34.65% variation for W-Rh combination with 30 kVp).

Objetivo: Apresentar uma ferramenta de análise de dados que pode ser utilizada para proteção de pacientes e traba- lhadores em áreas de uso de equipamentos móveis. Materiais e Métodos: Foi desenvolvida uma ferramenta, em pla- nilha ativa Excel®, que utiliza medidas de exposição para gerar um banco de dados de fatores de forma e calcular o kerma no ar ao entorno de um leito. O banco de dados inicial foi coletado com três equipamentos móveis. Um espalhador não antropomórfico foi utilizado, sendo realizadas medidas de exposição em uma malha de (4,2 × 4,2) m2, ao passo de 0,3 m. Resultados: A ferramenta calcula o kerma no ar (associado à exposição de pacientes expostos e ao equiva- lente de dose ambiente) à radiação secundária. Para distâncias inferiores a 60,0 cm, valores acima do limite máximo de equivalente de dose ambiente definido para área livre (0,5 mSv/ano) foram verificados. Os dados coletados a 2,1 m foram sempre inferiores a 12% do referido limite. Conclusão: A ferramenta é capaz de auxiliar na proteção radiológica de pacientes e trabalhadores, quando associada à coleta de dados adequada, pois possibilita a determinação de áreas livres ao entorno de leitos em áreas onde equipamentos móveis geradores de radiação X são utilizados. Objective: To present a data analysis toolkit that may be utilized with the purpose of radiation protection of hospital inpatients and workers in areas where mobile apparatuses are used. Materials and Methods: An Excel® ActiveSheet was utilized to develop a computational toolkit with exposure measurements to generate a database of shape factors and to calculate the air kerma around hospital beds. The initial database included data collected with three mobile apparatuses. A non-anthropomorphic phantom was utilized and exposure measurements were performed on a (4.2 × 4.2) m2 mesh-grid at 0.3 m steps. Results: The toolkit calculates the air kerma (associated with patients’ radiation exposure and with ambient equivalent dose) under secondary radiation. For distances lower than 60.0 cm, values above the maximum ambient equivalent dose threshold defined for radiation free areas (0.5 mSv/year) were verified. Data collected at 2.1 m have always presented values lower than 12% of that threshold. Conclusion: The toolkit can aid in the radiological protection of patients and workers, provided it is combined with appropriate data collection, since it allows the determination of radiation free areas around beds in rooms where mobile X-ray apparatuses are utilized.

Purpose Recently, we proposed the use of the synchrotron radiation (SR) beam for a new rotational radiotherapy technique for breast cancer treatment (SR3T) [1] ;. In this work, we show, via Monte Carlo (MC) simulations, the potential of SR3T also for application in breast radiosurgery with the patient in prone position. Methods We simulated the irradiation condition of the breast rotational radiosurgery with a MC code based on GEANT 4 toolkit. The pendant breast was modeled as a polyethylene cylinder with a diameter of 14 cm and height of 9 cm with a 1-cm tumor simulated in the centre or at 4 cm from the cylinder axis. A monoenergetic laminar SR beam of size 1.5 cm × 1.0 cm with energy ranging between 60 and 120 keV irradiated the phantom during a complete rotation with the center of rotation along the tumor mass. Results A collimated SR beam irradiating a pendant breast produces a dose distribution peaked at the center of rotation. MC simulations showed that is possible to perform partial-breast irradiation with a skin sparing comparable with that from a conventional MV breast radiotherapy. Conclusions We proposed a kV SR beam for partial-breast irradiation, for breast radiosurgery in the treatment of small lesions. We foresee the use of dose-enhancement agents in order to improve the dose to the target volume with proper sparing of healthy tissues.

OBJETIVO: O objetivo deste trabalho foi obter a distribuição da dose absorvida no ar numa sala de mamografia durante a simulação de um exame mamográfico, visando a reavaliar a necessidade do uso de barreiras de proteção radiológica nessas salas e a exposição das pacientes. MATERIAIS E MÉTODOS: Os dados da dose absorvida no ar foram coletados mediante simulação de exame mamográfico de um simulador de mama de BR12, em um equipamento Senograph 600T-Senix HF. Para tal, 158 pastilhas de CaSO4 foram distribuídas em malhas retangulares em torno do bucky, em três alturas distintas. RESULTADOS: O valor mais elevado da dose absorvida no ar, registrado no ponto central da superfície do simulador, centralizado no feixe primário, foi de 8,33 mGy, enquanto o menor valor registrado, devido exclusivamente ao espalhamento, foi de 0,008 mGy. CONCLUSÃO: Estes resultados indicam que o uso de blindagem adicional nas salas de mamografia pode não ser necessário na incidência crânio-caudal, desde que as distâncias consideradas neste trabalho sejam observadas. No entanto, eles enfatizam a necessidade de proteção da paciente. OBJECTIVE: The present study was aimed at evaluating the absorbed dose in air in a medical examination room during a mammography simulation, to re-evaluate the level of patients' exposure as well as the necessity of radiological protection barriers. MATERIALS AND METHODS: Data regarding absorbed dose in air were collected during mammography simulation with a BR12 breast phantom in a Senograph 600T-Senix HF mammograph. For this purpose, 158 CaSO4 dosimeters were distributed over rectangular grids around the bucky at three different heights. RESULTS: The highest value for absorbed dose in air recorded on the center of the phantom surface and centralized on the primary beam was 8.33 mGy, while the lowest value recorded exclusively due to radiation scattering was 0.008 mGy. CONCLUSION: These results indicate that the utilization of additional shielding in mammography facilities might not be necessary for craniocaudal acquisition, provided the distances considered for the present study are observed. However, the necessity of radiation protection of the patient should be emphasized.

OBJETIVO: Desenvolver um programa computacional para avaliar e controlar as características das curvas sensitométricas. MATERIAIS E MÉTODOS: Para o desenvolvimento do programa, foi elaborado um método de obtenção dos valores das características sensitométricas, de filmes de baixo e alto contraste, sem a necessidade da fixação de degraus de referência. RESULTADOS: O programa, denominado Sensito, foi implementado e testado utilizando dados sensitométricos de curvas características dos departamentos de radiologia convencional, hemodinâmica e mamografia. Ficou comprovada a possibilidade da análise das curvas sensitométricas destas áreas sem a necessidade de ajustes, dependentes dos usuários, e sem incorrer em desvios nos parâmetros sensitométricos avaliados e na variação destes. CONCLUSÃO: O programa possibilita a criação de um banco de dados de curvas sensitométricas para diferentes processadoras de uma instituição, gerando com facilidade as curvas sensitométrica e gama, de um registro, e os gráficos de constância das características sensitométricas avaliadas, fornecendo importante ferramenta para manter o controle sensitométrico.

Fluoroscopic barium meal (BM) studies are largely used around the world and very common to be performed in children. The medical and occupational exposures are important parameters that need to be investigated to evaluate the radiological effects. Calibration of the dosimeter used for exposure measurement is usually done with primary X-ray beam. The difference in energy spectra of primary and scattered radiation can influence obtained results. The main objective of this work is to evaluate the X-ray scattered spectra by different pediatric phantoms (simulation of patients subjected to BM procedures) to calculate an energy correction factor to the absorbed energy by the thermoluminescent dosimeters (TLD). To perform this evaluation, the TLDs were positioned over three areas in two occupational workers eyes, thyroid and hands. The Geant4 toolkit was used to define the spectra that reached TLDs and made possible to correct entrance surface air kerma. The present work was developed in two stages: (i) evaluation of scattered spectra by different standard phantoms (newborn, 1 year old, 5 years old and 10 years old); (ii) definition of the energy correction factor to the absorbed energy by each TLD. The results of this work show that Geant4 is a good toolkit to these analysis making possible to generate a correction factor considering a primary spectrum of 60 keV.

Concepts, methods and tools relevant to assessing the reliability of Monte Carlo simulation in sensitive experimental applications are briefly reviewed. An overview of ongoing research in the domain of simulation validation and related activities, such as software quality evaluation and uncertainty quantification, is summarized.

The Inverse Square Law (ISL) is a mathematical rule used to adjust the KERMA and exposure to different distances of focal spot having as reference a determined point in space. Taking into account the limitations of this rule and its application, we have as main objective to verify the applicability of ISL to determine exposure on radiodiagnostic area (maximum tensions between 30kVp and 150kVp). Experimental data was collected, deterministic calculation and simulation using Monte Carlo Method (Geant4 toolkit) were applied to conventional radiology and mammography. The experimental data was collected using a calibrated ionizing chamber TNT 12000 from Fluke. The conventional X-ray equipment used was a Multix Top of Siemens, with Tungsten track and total filtration equivalent to 2.5 mm of aluminum; and the mammographic equipment was a Mammomat Inspiration from Siemens, presenting the track-add filtration combinations of Molybdenum-Molybdenum, Molybdenum-Rhodium, Tungsten-Rhodium. Both equipments have the Quality Control testes in agreement to Brazilian regulations. Based on the results it is possible conclude that the ISL presents lower performance in correct measurements on mammography spectra, i.e. the associated error (differences) achieves a value up to 77.8% and it can cause significant impact on both areas depending on the spectra energy and distance to correct.

Some data analysis methods typically used in econometric studies and in ecology have been evaluated and applied in physics software environments. They concern the evolution of observables through objective identification of change points and trends, and measurements of inequality, diversity and evenness across a data set. Within each analysis area, various statistical tests and measures have been examined. This conference paper summarizes a brief overview of some of these methods.

INTRODUCTION: The objective of this paper is to verify the influence of the source geometry on Geiger Müller (GM) exposure rate data. This paper presents a validation of an application based on Monte Carlo (MC) data simulated using Geant4, based on a comparison of the exposure rates calculated via MC and Deterministic Calculations (DC) to experimental (measured) exposure rates. METHODS: Experimental data that were collected through measurements of standard sources were used for MC and DC validation. In addition, the best method of analyzing the impact of the real source geometry on calculations of a descarpack box of radioactive waste was verified. Furthermore, were estimated the exposure rates from a homogeneous solid waste box (used at clinical sites) and from a point source. These results were compared to confirm possible discrepancies related to source geometry in exposure rates collected using a GM detector. RESULTS: The investigated estimation methods were statistically compared; the MC presented higher agreement with the experimental data than did the deterministic calculations. The impact of considering a point source instead of the real geometry (descarpack box) was an underestimation of between 20% and 70%, depending on the source - detector distance and the isotope evaluated. CONCLUSION: The DC always presented a higher difference with respect to the experimental data than did the MC calculation. The use of realistic geometry proved to exert a significant impact on the exposure rate data for solid radioactive waste compared with the exposure rate induced by a point source; the exposure rate estimation obtained using the real geometry was always at least 16% higher than the estimation obtained for a point source, and some differences greater than 50% were found.

The opportunity to work for the first time with real data from the LHC experiments, at CERN, becomes reality for students around the world through the Masterclass Hands on CERN, the outreach activity organized by CERN where more than 10000 students from 37 countries and 160 universities take part each year. Through video conferencing students from different countries get together to discuss the results of their analysis using events from ATLAS, CMS, or ALICE experiments , coordinated by 2 physicists at CERN, or Fermilab. The goal is to give students a glimpse of the routine work of physicists within the international collaborations that assemble and perform these experiments. The official language is English. The Internacional Masterclass - Hands on Particle Physics is heavily based on computing technologies. The World Wide Web plays a major role allowing the videoconferences, the access to the data from the LHC experiments. Facebook has been added to the facilities the students can use to access all the information about the Masterclass and plan their participation. We will report about our experience in Rio de Janeiro, Brazil, working with the Masterclass, where the World Wide Web is also used to explain the introductory concepts of Particle Physics. Sites with introductory explanations, some of them in Portuguese, can be accessed any time by the students. Local pages on Facebook allows them to be in contact with the physicists taking part in the project. E-mail is normally used by their teachers. Skype allows meetings, conversations and even short courses with students and teachers far away from our university. Altogether bringing them into the HEP world.

Various issues related to the complexity of apprais- ing the capabilities of physics models implemented in Monte Carlo simulation codes and the evolution of the functional quality the associated software are considered, such as the dependence on the experimental environment where the software operates and its sensitivity to detector characteristics. The concept of software validity as relative to the environment is illustrated by means of a real-life experimental test case. Methods and techniques to mitigate the risk of deteriorating the quality of the software are critically discussed: they concern various disciplines of the software development process. Quantitative validation of physics models is advocated as a method to appraise their capabilities objectively and to monitor the evolution of their associated software behavior., Comment: To be published in the Proceedings of IEEE Nuclear Science Symposium 2013

This work provides a critical analysis of the point source methodology applied in nuclear medicine radioactivity waste management routine. To evaluate the point source approximation used in the practice to determine the activity and its effect on activity and storage time was used deterministic and Monte Carlo calculations. The first step of this work was to validate the Monte Carlo Geant4 toolkit using measurements with standard calibration sources. After that the deterministic and Monte Carlo calculation was performed. In a realistic geometry the waste is not a point source but a box of dimensions (30.5 x 31.5 x 25.0) cm3. The impact on activity estimation comparing the real source point to the box geometry was observed from 20% up to 800% depending on the distance between the source and the detector and the selected radionuclide. The simple case evaluated in this work considering different radioisotopes proves that uses the point source approximation cause significant influence on the activity estimation. However it does not have significant impact in the storage time. The non significant influence in time storage can be explained by the activity limits recommend to release the radioactive waste that is significant smaller than the initial activity and the exponential behavior of the radioactive decay associated to value of the physical disintegration constant for the radionuclide commonly used on nuclear medicine applications.

Ongoing investigations for the improvement of Geant4 accuracy and computational performance resulting by refactoring and reengineering parts of the code are discussed. Issues in refactoring that are specific to the domain of physics simulation are identified and their impact is elucidated. Preliminary quantitative results are reported., To be published in the Proc. CHEP (Computing in High Energy Physics) 2012

OBJETIVOS: Avaliar o efeito do cimento α-TCP combinado com PRP sobre a osteogênese, comparando os resultados com PRP utilizado isoladamente. MÉTODOS: Foi confeccionado defeito bilateral no fêmur de ratos e preenchido com um dos dois tipos de tratamentos (PRP ou α-TCP+PRP), sendo avaliado em quatro e oito semanas. As imagens radiográficas forneceram valores da área da lesão, e a histologia (coloração Picrosirius) indicou a área de neoformação óssea. RESULTADOS: As médias referentes à área de lesão do grupo α-TCP+PRP (2,64mm² ± 2,07 e 1,91mm² ± 0,93; quatro e oito semanas, respectivamente) demonstraram numericamente melhores resultados, porém não significativos (p > 0,05), em comparação com aqueles observados no grupo PRP (5,59mm² ± 2,69 e 3,23mm² ± 1,46; quatro e oito semanas, respectivamente). As médias de neoformação óssea foram de 62,7% ± 12,1% e 79,01% ± 6,25 no grupo PRP, e 73,3% ± 12,7 e 85,86% ± 10,45 no grupo α-TCP+PRP, em quatro e oito semanas, respectivamente (p > 0,05). CONCLUSÃO: Os dados deste estudo sugerem que o tratamento com cimento α-TCP combinado com PRP não demonstra diferença significativa quando comparado ao PRP isolado. Entretanto, há um possível efeito precoce sobre a regeneração óssea quando os dois biomateriais são aplicados em conjunto. OBJECTIVES: To evaluate the effect of alpha-tricalcium phosphate (α-TCP) cement combined with platelet-rich plasma (PRP) on osteogenesis, and to compare the results with use of PRP alone. METHODS: A bilateral defect was produced in rat femurs and was filled with one of two types of treatments (PRP or α-TCP + PRP). The outcomes were evaluated after four and eight weeks. Radiographic images provided values for the lesion area, and histology (picrosirius staining) indicated the area of new bone formation. RESULTS: The means relating to the lesion area of the α-TCP + PRP group (2.64 ± 2.07 and 1.91 ± 0.93 mm², after four and eight weeks, respectively) showed numerically better but non-significant results (p > 0.05) than those seen in the PRP group (5.59 mm ² ± 2.69 and 3.23 ± 1.46 mm ², after four and eight weeks, respectively). The mean new bone formation rates were 62.7% ± 12.1 and 79.01% ± 6.25 in the PRP group, and 73.3% ± 12.7 and 85.86% ± 10.45 in α-TCP + PRP group, after four and eight weeks, respectively (p > 0.05). CONCLUSION: The data from this study suggest that treatment with α-TCP cement combined with PRP does not show any significant difference in comparison with PRP alone. However, there is a possible early effect on bone regeneration when the two biomaterials are applied together.

Quantification of clinical parameters in osteoarthritis (OA) diagnosis is important for the health professionals' intervention. The purpose of this study was to develop a computational toolkit that quantifies morphologic, anthropomorphic and mathematical parameters of the lower limb to help those professional on periodical evaluation of patients. The developed toolkit is reliable, semiautomatic and reproductive. This toolkit considers the influence of image amplification and distortions. Its functions were validated in two different ways: through a non-anthropomorphic and an anthropomorphic calibration system of known dimensions. Accuracy and reproducibility were determined with the calibration systems prior to the use of the toolkit to analyze human X-rays images of OA patients. The tool allows a safe evaluation of the patient for two-dimensional images. Today the follow-up of OA is accomplished with computerized tomography, which increases the patient's absorbed dose. This is potentially harmful due to the increased radiosensitive effects of this radiation (possibly affecting blood production) increasing the risk of those patients that need periodical evaluations. The developed toolkit was able to quantify morphologic, anthropomorphic and mathematical parameters of the lower limb, reducing the subjectivity of the evaluation of bi-dimensional X-rays images.

In geology the simulation of the sedimention process deposition is very used on different kind of studies. However a great problem is to get the information without destroy the architecture of the deposited material (since now named testimonial). Usually they do slice the real sample and they take pictures of it. However this technique is too aggressive (invasive) and usually cause damage to the testimonial. This work aim is to define characteristic of imaging these testimonial to use the medical imaging processing techniques for the analysis of objects made up of coal. Two objects were imaged: a short testimonial with acrylic resin, called Model Carbonated with Acrylic (MCA), and a greater testimony, contained within a PVC container and immersed in water, called Model Carbonated Aquarius (MCAq). Were generated plot profiles and images based on the topogram and sonogram, showing its good contrast and resolution.

Different authors publish about the transmission curves as a function of shielding material thickness. It is important to define these curves of transmission of photons using the material composition available and regularly commercialized. So the objective of this work was to simulate the transmission data and to generate the transmission curves as function of different material composition as function of the thickness to the spectrum energy used on PetCT. That way we simulate an incoming monoenergetic photons beam of 511 keV. Were collected in sensitive volume the absorbed energy and the photon flux on spherical sensitive volume with a radius of 1.0cm composed of air. We simulated two sensitive volumes one before and one after the shielding wall. We simulate shielding wall made of: lead; concrete, described according Simpkin and ICRU 44 documentation; iron alloy composed by 1% of carbon and barite mortar. The curves of transmission were compared to other simulated data and to real data. As results we generate a group of data and fitting curves applied to the medical application getting concordance to the previously published data and the real data collected. We generated curves of transmission data for barite mortar, undefined for these applications until now.

The silicone gel implant for breast have been, more and more, a common procedure among women of different ages around the world. That way it is important to know how it can affect the dose on sensitive tissues around the implanted silicone. On this work we are studying the influence on absorbed dose distribution map into the patient, especially on tissues close to the silicone implant for diagnostic radiological procedures comparing a map of dose distribution for voxel model simulating patients with and without breast silicone implant. So three models of woman trunk considering were built considering the breasts with and without silicon implant. The three developed models were introduced into Geant4 code (version 9.2.p01) and were simulated three different parallel beam sources: frontal, lateral and rotational. The photons energy were sorted considering the distribution that represents the x-radiation spectra emitted by a tungsten target and considers additional filtration of 3mmAl at difference peak tensions. For all the studied cases the simulations considering the anterior-posterior exposures positioning of silicone implant produce a significant increase on glandular dose. For peak tension of 80kVp was calculated having a mean increase on glandular dose of 12% for the both breast simulated with silicone implant over and under the pectoral muscle. This difference decrease when the kVp increase been registered a mean value of 4,5% for the peak tension of 120kVp. There was no significant difference for the absorbed glandular dose calculated for the lateral positioning exposure, been presented differences always under 3,5% for 80kVp spectra. For higher kVp the differences presented were inferior to the statistical fluctuation due the simulation process. As conclusion the simulations realized in this work shown that the presence of silicone implant can, considering some cases, increase significantly the glandular dose due the backscattering.

The aim of this work is to compare the dosimetric data and the photon fluency in three positions among different homogeneous models to a voxel model. Were simulated the mammographic dosimetric homogeneous models and a breast voxel model which represents 4.0 cm compressed woman breast, with 50% of glandular tissue. Were simulated the photon spectra of Mo-30Mo from 26 kVp up to 34 kVp; and Mo-25Rh from 26 kVp up to 34 kVp characterized by the HVL values. For all techniques simulated the normalized glandular dose was superestimated by the BR12 homogeneous models and underestimated by PMMA homogeneous models comparing to voxel model. Among the models studied was the model proposed by Dance that presented a behavior similar to voxel model, however it underestimates all the D gN .

The ability to test scientific software needs to be supported by adequate software design. Legacy software systems are often characterized by the difficulty to test parts of the software, mainly due to existing dependencies on other parts. Methods to improve the testability of physics software are discussed, along with open issues specific to physics software for Monte Carlo particle transport. The discussion is supported by examples drawn from the experience with validating Geant4 physics.

OBJETIVO: Verificar o efeito da mudança no contraste do objeto, tempo de exposição e dose de radiação quando diferentes espessuras de filtração de molibdênio (Mo) e ródio (Rh) são empregadas em mamógrafos. MATERIAIS E MÉTODOS: Realizaram-se medidas da exposição na entrada da pele com uma câmara de ionização para diferentes espessuras para os filtros de Mo e Rh. Para determinar a dose glandular média foi utilizado simulador de BR12 (50% tecido adiposo e 50% tecido glandular) de diferentes espessuras (4 cm e 8 cm). Energias na faixa de 24 kVp a 34 kVp foram empregadas e filmes Kodak MinR 2000 foram utilizados. RESULTADOS: Os resultados evidenciaram dados de contraste do objeto, dose glandular e tempo de exposição para diferentes espessuras de filtros adicionais e diferentes tensões. Esses dados indicaram aumento nos valores de contraste do objeto e tempo de exposição, com o aumento da espessura dos filtros. A dose glandular apresentou comportamento com diferentes tendências para cada caso analisado. Equações foram definidas para possibilitar a estimativa do contraste do objeto, dose glandular e tempo de exposição para os casos estudados. CONCLUSÃO: Os resultados possibilitaram a estimativa de equações que auxiliam na verificação do comportamento do contraste do objeto e da dose glandular para simuladores com espessura de 4 cm e 8 cm e para os filtros de Rh e Mo. Dessa forma, torna-se possível estimar a figura de mérito (razão entre o contraste do objeto e a dose glandular), podendo auxiliar na análise da relação risco-benefício dos casos estudados. OBJECTIVE: Our purpose was to verify the effect of changes in subject contrast, exposure time and radiation dose when different thicknesses of molybdenum (Mo) and rhodium (Rh) filters are used in mammography equipments. MATERIALS AND METHODS: Entrance skin exposure measurements were performed with an ionization chamber for different thicknesses of Mo and Rh filters. Average glandular dose was determined with a BR12 simulator (50% fat tissue and 50% glandular tissue) of different thicknesses (4 cm and 8 cm). Energies in the range of 24 to 34 kVp and Kodak MinR 2000 films were used. RESULTS: Results have evidenced data on subject contrast data, glandular dose and exposure time for different thicknesses of additional filters and different kVp values. These data have indicated an increase both in values of subject contrast and exposure time when filters thickness is increased. The glandular dose has presented a different behavior tendency for each case analyzed. Equations were defined to allow us to estimate subject contrast, glandular dose and exposure time for the cases studied. CONCLUSION: The results have made possible to define equations to assist with the evaluation of subject contrast and glandular dose behavior in simulators with 4 cm and 8 cm thicknesses and for Rh and Mo additional filters. In this way, it is possible to estimate the figure of merit (subject contrast/glandular dose ratio) to assist in the risk-benefit analysis of the cases studied.

Purpose: The objective of this study is to realize a computational dosimetry on a simplified model of miocardic perfusion, considering the usual different ways to describe the spectra emitted for Tc‐99m. Method and Materials: The GEANT4 code was used to simulate two geometries: the radial dose distribution from an isotropic point source described by the three spectra, modeled with photon emission from the center of a 1.3‐m‐diam sphere of muscle tissue; and a second considering an uniform distribution of Tc‐99m in the heartmuscle of the adult male voxel model MAX, to take the organs dose distribution. The different ways to describe the spectra emitted for Tc‐99m was: monoenergetic spectrum of 140 keV; three photonsemissions spectrum (2.1, 141 and 143 keV) and total spectrum (including characteristics x‐rays and Auger electrons).Results: For distance low than 1 cm from the point source the radial dose distribution is higher for total spectrum. The radiation dose in a sphere with 0.01 mm defined at the center of the sphere of muscle was 0.369 mGy Bq1 h1 (total spectrum), 0.276 mGy Bq1 h1 (three photonspectrum), and 0.005 mGy Bq1 h1 (monoenergetic spectrum). This data shown that include Auger electrons,characteristic x‐rays, and low energy gamma give a significant contribution to total energy deposition. This results corroborates the simulations realized using the voxel model. The data variation shown that monoenergetic and three gamma spectra, comparing to total spectra simulated, produce a decrease on absorbed dose on cardiac tissue of 19.2% and 7.1%, respectively. Conclusion: The results shown that the combined transport of electrons Auger and characteristics x‐rays of the Tc‐99m increase the radiation dose, especially on organs/tissues closer to those have had absorbed the radiopharmaceuticals. This study indicates the importance on describe the complete radiopharmaceuticalsspectrum on dosimetric simulations in Nuclear Medicine.

The aim of this work was to investigate the influence of the eyelid on the absorbed dose distribution in eye tissues. The study was performed using two versions of the female adult head phantom (FeH) connected to the GEANT4 Monte Carlo code: one has the eyes open and the second, closed. The calculations of organ dose, normalised to air KERMA free-in-air, were done for external exposures to photon radiation with energies between 10 and 200 keV. Three parallel beam sources were studied: anterior-posterior, left lateral and rotational. The doses between the two phantoms were compared with evident differences. The results show that for photon sources with energies lower than 30 keV, the attenuations by the eyelid are relevant in reducing the dose in the eye lens and cornea. This suggests that medical exposure protocols that use this energy range should consider advising patients to close their eyes during the exposure.

Purpose: To compare conversion coefficient of KERMA free in air to glandular dose, in mammography, simulated to BR12 model and a realistic breast voxel model. Method and Materials: We simulate the glandular dose (Dg) and KERMA free in air (Kai), using the Monte Carlo program MCNP (version 4B) to estimate the conversion coefficient (cg) of KERMA free in air at entrance skin in glandular dose. The computational universe generated to simulate a mammographic procedure mimics LORAD III mammographic equipment. The focal spot of molybdenum irradiates photons isotropically in a solid angle of 16.8°. The bucky is 0.6190 m far from de focal spot. Above the model there is a PMMA compress paddle 0.002 m thicker. The add filtration (30 μm Mo thicker and 25 μm Rh thicker) was located at 0.050 m far from the focal spot. Tow spectra were used in voxel model simulations: 28 kVp with Mo add filtration and 30 kVp with Rh add filtration. Results: The cg presented on Mo/Rh simulation was 1.5 times larger than the presented on Mo/Mo simulation. Comparing the voxel model to the BR12 model we have actually a super estimation on both simulated cg values: 3.4 times considering the simulation with Mo/Mo target/filter combination, and 2.4 times considering the simulation with Mo/Rh target/filter combination. Conclusion: The cg values show a decrease of 58.7% considering the Mo/Rh target/filter combination and a decrease of 70.2% considering the Mo/Mo target/filter combination, to the realistic breast model as comparative pattern. These variation on cg are probably caused by the definition of a non‐anthropomorphic model composed by an homogeneous distribution of tissues as pattern, that makes unviable the observation of the absorbed energy by each tissue; and because this model do not consider the position of glandular tissue in the real breast geometry.

Objectives: To evaluate the effect of alpha-tricalcium phosphate (α-TCP) cement combined with platelet-rich plasma (PRP) on osteogenesis, and to compare the results with use of PRP alone. Methods: A bilateral defect was produced in rat femurs and was filled with one of two types of treatments (PRP or α-TCP + PRP). The outcomes were evaluated after four and eight weeks. Radiographic images provided values for the lesion area, and histology (picrosirius staining) indicated the area of new bone formation. Results: The means relating to the lesion area of the α-TCP + PRP group (2.64 ± 2.07 and 1.91 ± 0.93 mm2, after four and eight weeks, respectively) showed numerically better but non-significant results (p > 0.05) than those seen in the PRP group (5.59 mm 2 ± 2.69 and 3.23 ± 1.46 mm 2, after four and eight weeks, respectively). The mean new bone formation rates were 62.7% ± 12.1 and 79.01% ± 6.25 in the PRP group, and 73.3% ± 12.7 and 85.86% ± 10.45 in α-TCP + PRP group, after four and eight weeks, respectively (p > 0.05). Conclusion: The data from this study suggest that treatment with α-TCP cement combined with PRP does not show any significant difference in comparison with PRP alone. However, there is a possible early effect on bone regeneration when the two biomaterials are applied together.