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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.

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.

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.

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.

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.

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 .

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.