RESUMO
The design and implementation of a mobile gamma spectrometry system to in vivo measure the accumulated activity of 131I in whole body and thyroid of patients with thyroid diseases are presented in this work. This system may be used for both pre-therapeutic and post-therapeutic dosimetry calculations. It consists of a detector and a movable support that allows its movement from one place to another.
Assuntos
Radioisótopos do Iodo/análise , Radiometria/instrumentação , Espectrometria gama/instrumentação , Doenças da Glândula Tireoide/radioterapia , Adulto , Desenho de Equipamento , Feminino , Humanos , Hipertireoidismo/metabolismo , Hipertireoidismo/radioterapia , Radioisótopos do Iodo/farmacocinética , Pessoa de Meia-Idade , Imagens de Fantasmas , Radiometria/estatística & dados numéricos , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Espectrometria gama/estatística & dados numéricos , Doenças da Glândula Tireoide/metabolismo , Glândula Tireoide/metabolismo , Glândula Tireoide/efeitos da radiação , Neoplasias da Glândula Tireoide/metabolismo , Neoplasias da Glândula Tireoide/radioterapiaRESUMO
This work introduces a new, versatile and robust X-ray detector with hemispherical 2π geometry, based on a set of 15 small cylindrical proportional counters located in a hexagonal and pentagonal fullerene C60 pattern, at the same distance from the center (where a sample is placed). The counteranode consists of stainless steel sewing needles with spherical tips measuring approximately 80 µm in diameter. The space between the counters and the sample could contain air, the same gas as the counters or vacuum. This allows a significant increase in the count rates by a factor approximately equal to the number of counters connected. It is shown that an energy resolution of 20% for 5.9 keV photons can be obtained, and a global counting rate of around 10(6)counts/s is achievable by the 15 Needle Anode Proportional Counters (NAPCs) operating in parallel mode, in our setup.
Assuntos
Radiometria/instrumentação , Eletrodos , Desenho de Equipamento , Humanos , Fótons , Radiometria/estatística & dados numéricos , Raios XRESUMO
This paper aims to evaluate the feasibility of applying LiF:Mg,Ti microdosimeters as a new method of dosimetry to volumetric-modulated arc therapy (VMAT) RapidArc. The response of microdosimeters presented a maximum variation of ±3.18% and ±0.510% using optically stimulated luminescence (OSL) and thermoluminescence (TL) techniques, respectively. Although studies were conducted on LiF:Mg,Ti microdosimeters previously, the microdosimeters in this study showed precision and high potential of application in VMAT dosimetry and in the verification of treatment planning using the VMAT technique.
Assuntos
Radiometria/métodos , Radioterapia de Intensidade Modulada/normas , Fluoretos , Humanos , Compostos de Lítio , Luminescência , Magnésio , Imagens de Fantasmas , Polimetil Metacrilato , Controle de Qualidade , Radiometria/instrumentação , Radiometria/estatística & dados numéricos , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Radioterapia de Intensidade Modulada/estatística & dados numéricos , Dosimetria Termoluminescente/instrumentação , Dosimetria Termoluminescente/métodos , Dosimetria Termoluminescente/estatística & dados numéricos , TitânioRESUMO
The development of new medical devices possess a number of challenges, including designing, constructing, and assaying prototypes. In the case of new brachytherapy seeds, this is also true. In this paper, a methodology for rapid dosimetric characterization of (125)I brachytherapy seeds during the early stages of their development is introduced. The characterization methodology is based on the joint use of radiochromic and personal monitoring photographic films in order to determine the planar anisotropy due to the radiation field produced by the seed under development, by means of isodose curves. To evaluate and validate the process, isodose curves were obtained with both types of films after irradiation with a commercial (125)I brachytherapy seed.
Assuntos
Braquiterapia/métodos , Anisotropia , Braquiterapia/instrumentação , Dosimetria Fotográfica/métodos , Dosimetria Fotográfica/estatística & dados numéricos , Humanos , Radioisótopos do Iodo/uso terapêutico , Radiometria/métodos , Radiometria/estatística & dados numéricos , Dosagem RadioterapêuticaRESUMO
As a part of the project concerning the irradiation of a section of the human liver left lobe, a preliminary estimation of the expected dose was performed. To obtain proper input values for the calculation, neutron flux and gamma dose rate characterization were carried out using adequate portions of cow or pig liver covered with demineralized water simulating the preservation solution. Irradiations were done inside a container specially designed to fulfill temperature preservation of the organ and a reproducible irradiation position (which will be of importance for future planification purposes). Implantable rhodium based self-powered neutron detectors were developed to obtain neutron flux profiles both external and internal. Implantation of SPND was done along the central longitudinal axis of the samples, where lowest flux is expected. Gamma dose rate was obtained using a neutron shielded graphite ionization chamber moved along external surfaces of the samples. The internal neutron profile resulted uniform enough to allow for a single and static irradiation of the liver. For dose estimation, irradiation condition was set in order to obtain a maximum of 15 Gy-eq in healthy tissue. Additionally, literature reported boron concentrations of 47 ppm in tumor and 8 ppm in healthy tissue and a more conservative relationship (30/10 ppm) were used. To make a conservative estimation of the dose the following considerations were done: i). Minimum measured neutron flux inside the sample (approximately 5 x 10(9) n cm-2 s-1) was considered to calculate dose in tumor. (ii). Maximum measured neutron flux (considering both internal as external profiles) was used to calculate dose in healthy tissue (approximately 8.7 x 10(9) n cm-2 s-1). (iii). Maximum measured gamma dose rate (approximately 13.5 Gy h-1) was considered for both tumor and healthy tissue. Tumor tissue dose was approximately 69 Gy-eq for 47 ppm of (10)B and approximately 42 Gy-eq for 30 ppm, for a maximum dose of 15 Gy-eq in healthy tissue. As can be seen from these results, even for the most conservative case, minimum tumor dose will be acceptable from the treatment point of view, which shows that the irradiation conditions at this facility have quite good characteristics for the proposed irradiation.
Assuntos
Terapia por Captura de Nêutron de Boro/instrumentação , Neoplasias Hepáticas/radioterapia , Radiometria/instrumentação , Radiometria/estatística & dados numéricos , Planejamento da Radioterapia Assistida por Computador/estatística & dados numéricos , Animais , Argentina , Terapia por Captura de Nêutron de Boro/estatística & dados numéricos , Nêutrons Rápidos/uso terapêutico , Raios gama/uso terapêutico , Humanos , Técnicas In Vitro , Neoplasias Hepáticas/secundário , Neoplasias Hepáticas/cirurgia , Transplante de Fígado , Reatores Nucleares , Suínos , Transplante AutólogoRESUMO
In Brazil there are over 100 high dose rate (HDR) brachytherapy facilities using well-type chambers for the determination of the air kerma rate of 192Ir sources. This paper presents the methodology developed and extensively tested by the Laboratorio de Ciencias Radiologicas (LCR) and presently in use to calibrate those types of chambers. The system was initially used to calibrate six well-type chambers of brachytherapy services, and the maximum deviation of only 1.0% was observed between the calibration coefficients obtained and the ones in the calibration certificate provided by the UWADCL. In addition to its traceability to the Brazilian National Standards, the whole system was taken to the University of Wisconsin Accredited Dosimetry Calibration Laboratory (UWADCL) for a direct comparison and the same formalism to calculate the air kerma was used. The comparison results between the two laboratories show an agreement of 0.9% for the calibration coefficients. Three Brazilian well-type chambers were calibrated at the UWADCL, and by LCR, in Brazil, using the developed system and a clinical HDR machine. The results of the calibration of three well chambers have shown an agreement better than 1.0%. Uncertainty analyses involving the measurements made both at the UWADCL and LCR laboratories are discussed.
Assuntos
Braquiterapia/normas , Radiometria/normas , Ar , Fenômenos Biofísicos , Braquiterapia/estatística & dados numéricos , Brasil , Humanos , Radioisótopos de Irídio/administração & dosagem , Radioisótopos de Irídio/uso terapêutico , Radiometria/instrumentação , Radiometria/estatística & dados numéricos , Planejamento da Radioterapia Assistida por Computador/estatística & dados numéricos , Padrões de Referência , Espalhamento de RadiaçãoRESUMO
A dosimetry intercomparison between the boron neutron capture therapy groups of the Massachusetts Institute of Technology (MIT) and the Comisión Nacional de Energía Atómica (CNEA), Argentina was performed to enable combined analyses of NCT patient data between the different centers. In-air and dose versus depth measurements in a rectangular water phantom were performed at the hyperthermal neutron beam facility of the RA-6 reactor, Bariloche. Calculated dose profiles from the CNEA treatment planning system NCTPlan that were calibrated against in-house measurements required normalizations of 1.0 (thermal neutrons), 1.13 (photons), and 0.74 (fast neutrons) to match the dosimetry of MIT.
Assuntos
Terapia por Captura de Nêutron de Boro/estatística & dados numéricos , Terapia por Captura de Nêutron de Boro/normas , Radiometria/estatística & dados numéricos , Argentina , Calibragem , Humanos , Massachusetts , Radiometria/normas , Dosagem Radioterapêutica , Valores de Referência , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
DoseCal software has been used to evaluate the Entrance Surface Dose (ESD) and Effective Dose (ED) of adult patients undergoing abdomen, cervical spine, chest, lumbar spine and skull diagnostic X-ray examinations in AP, PA and LAT projections. The survey was carried out in nine hospitals in Rio de Janeiro state with a total of 1917 radiographs. The mean values of ESD (mGy) and ED (mSv) were recorded. Although the results obtained are below the international diagnostic reference levels, they present large variations within and between hospitals which reflects the disparity of radiographic techniques used in the examinations. The results were compared with the European Community Reference Levels. Even though in Brazil there are specific legislations on radiation protection and implementation of Quality Assurance Programs (QAPs) in all medical institutions, there is still a need for personnel training and national guidance on good practice for optimization of patients' doses.
Assuntos
Carga Corporal (Radioterapia) , Exposição Ambiental/análise , Exposição Ambiental/estatística & dados numéricos , Doses de Radiação , Radiografia/estatística & dados numéricos , Radiometria/estatística & dados numéricos , População Urbana/estatística & dados numéricos , Adulto , Brasil , Feminino , Humanos , MasculinoRESUMO
In an attempt to estimate the effective collective dose imparted to the population of Camagüey-Ciego de Avila territory, Cuba, we have made use of the statistics from nuclear medicine examinations given to a population of 1.1 million inhabitants for the years 1995-1999. The average annual frequency of examinations was estimated to be 3.82 per 1000 population. The results show that nuclear medicine techniques of thyroid imaging with 43.73% and thyroid uptake with 43.36% are the main techniques implicated in the relative contribution to the total annual effective collective dose, which averaged 54.43 man Sv for the studied period. Radiation risks for the Camagüey-Ciego de Avila population caused by nuclear medicine examinations in the period studied were calculated: the total number of fatal and non-fatal cancers was 16.33 and the number of serious hereditary disturbance was 3.54 as a result of 21,073 nuclear medicine procedures, corresponding to a total detriment of one case per thousand examinations.
Assuntos
Neoplasias Induzidas por Radiação/mortalidade , Medicina Nuclear/estatística & dados numéricos , Radiometria/estatística & dados numéricos , Cintilografia/estatística & dados numéricos , Eficiência Biológica Relativa , Medição de Risco/métodos , Carga Corporal (Radioterapia) , Cuba/epidemiologia , Feminino , Humanos , Incidência , Masculino , Especificidade de Órgãos , Doses de Radiação , Fatores de RiscoRESUMO
In this work, the MCNP4B code has been employed to calculate conversion coefficients from air kerma to the ambient dose equivalent, H*(10)/Ka, for monoenergetic photon energies from 10 keV to 50 MeV, assuming the kerma approximation. Also estimated are the H*(10)/Ka for photon beams produced by linear accelerators, such as Clinac-4 and Clinac-2500, after transmission through primary barriers of radiotherapy treatment rooms. The results for the conversion coefficients for monoenergetic photon energies, with statistical uncertainty <2%, are compared with those in ICRP publication 74 and good agreements were obtained. The conversion coefficients calculated for real clinic spectra transmitted through walls of concrete of 1, 1.5 and 2 m thick, are in the range of 1.06-1.12 Sv Gy(-1).
Assuntos
Simulação por Computador , Modelos Teóricos , Fótons , Radiometria/estatística & dados numéricos , Dosagem Radioterapêutica , Espectrofotometria/estatística & dados numéricos , Materiais de Construção , Método de Monte Carlo , Aceleradores de Partículas , Imagens de Fantasmas , Doses de Radiação , Proteção Radiológica/instrumentação , Software , Raios XRESUMO
The collaborative project involving the Mullard Space Science Laboratory (MSSL), Virgin Atlantic Airways (VAA), the UK Civil Aviation Authority (CAA) and the UK National Physical Laboratory (NPL) has been performing tissue-equivalent proportional counter measurements of cosmic ray doses in commercial aircraft since January 2000. In that time data have been recorded on over 700 flights, including over 150 flights with Air New Zealand (ANZ). This substantial set of data from the southern hemisphere is an ideal complement to the London-based measurements performed primarily on VAA flights. Although some ANZ data remains to be analysed, dose information from 111 flights has been compared with the CARI and EPCARD computer codes. Overall, the agreement between the measurements and EPCARD was excellent (within 1% for the total ambient dose equivalent), and the difference in the total effective doses predicted by EPCARD and CARI was <5%.
Assuntos
Aeronaves/estatística & dados numéricos , Algoritmos , Radiação Cósmica , Nêutrons , Exposição Ocupacional/análise , Exposição Ocupacional/estatística & dados numéricos , Radiometria/estatística & dados numéricos , Carga Corporal (Radioterapia) , Comércio/estatística & dados numéricos , Exposição Ambiental/análise , Desenho de Equipamento , Humanos , Internacionalidade , Nova Zelândia/epidemiologia , Doses de Radiação , Proteção Radiológica/métodos , Radioisótopos/análise , Radiometria/métodos , Eficiência Biológica Relativa , Reprodutibilidade dos Testes , Medição de Risco/métodos , Fatores de Risco , Sensibilidade e Especificidade , Reino Unido , Ilhas Virgens AmericanasRESUMO
This work presents the results of the determination of uranium concentration in the most commonly used phosphate fertilizers employed in Brazilian agricultural land. The technique employed was the nuclear fission track registration in plastic foils of Makrofol KG (dry method), together with a discharge chamber system for track counting. Phosphate fertilizer samples and uranium standards were irradiated together with thermal neutrons in the 2 MW IEA-R1 research reactor of IPEN/SP. The uranium concentration in Brazilian phosphate fertilizers ranging from 5.17 to 54.3 ppm is in good agreement with the results reported in the literature for similar fertilizers produced in other countries.
Assuntos
Fertilizantes/análise , Manufaturas/análise , Radiometria/instrumentação , Radiometria/métodos , Urânio/análise , Brasil , Contaminação Radioativa de Alimentos/análise , Contaminação Radioativa de Alimentos/prevenção & controle , Radiometria/estatística & dados numéricos , Contagem de Cintilação/instrumentação , Contagem de Cintilação/métodosRESUMO
This study aims to investigate a shielding design against neutrons and gamma rays from a source of 252Cf, using Monte Carlo simulation. The shielding materials studied were borated polyethylene, borated-lead polyethylene and stainless steel. The Monte Carlo code MCNP4B was used to design shielding for 252Cf based neutron irradiator systems. By normalising the dose equivalent rate values presented to the neutron production rate of the source, the resulting calculations are independent of the intensity of the actual 252Cf source. The results show that the total dose equivalent rates were reduced significantly by the shielding system optimisation.
Assuntos
Terapia por Captura de Nêutron de Boro/instrumentação , Califórnio/química , Análise de Ativação de Nêutrons/métodos , Nêutrons/efeitos adversos , Polietileno/química , Proteção Radiológica/métodos , Raios gama , Humanos , Método de Monte Carlo , Doses de Radiação , Radiobiologia , Radiometria/estatística & dados numéricosRESUMO
Este trabalho visa avaliar a profundidade de polimerizaçäo de 05 (cinco) aparelhos fotopolimerizadores em uso da Faculdade de Odontologia da UERJ. Os aparelhos fotopolimerizadores foram avaliados por meio de um medidor de intensidade de luz, o radiômetro (Demetron Curing Tadiometer). Este registrou a integridade luminosa emitida por cada aparelho durante 40 segundos. Uma correlaçäo entre intensidade de luz obtida pelo radiômetro e profundidade de polimerizaçäo foi alcançada
Assuntos
Resinas Compostas/efeitos da radiação , Luz , Radiometria/estatística & dados numéricosRESUMO
La comunidad médica nacional utiliza en su quehacer diario los beneficios de las radiaciones ionizantes para el diagnóstico y terapia de las enfermedades. Las dosis recibidas en el área médica son apenas una pequeña parte del total de radiación que recibimos durante el año. La presente revisión bibliográfica tiene varios objetivos, presentar los diferentes componentes que conforman las radiaciones naturales; introducir los productos de consumo humano que contienen fuentes radioactivas y que por lo tanto están exponiendo a nuestros cuerpos. Presentar argumentos para disminuir la tan común fobia a las radiaciones ionizantes y finalmente, introducir una magnitud dosimétrica de fácil entendimiento tanto para el médico, el técnico y el paciente. Descriptores: radiación, dosis, radiación natural, uranio, BERT
Assuntos
Humanos , Radiação de Fundo , Ingestão de Alimentos , Radiação , Controle da Radiação , Radiação Ionizante , Radiometria/estatística & dados numéricos , Costa RicaRESUMO
An exhaustive revision of dosimetry data for 192Ir, 125I, 103Pd and 169Yb brachytherapy sources has been performed by means of the EGS4 simulation system. The DLC-136/PHOTX cross section library, water molecular form factors, bound Compton scattering and Doppler broadening of the Compton-scattered photon energy were considered in the calculations. The absorbed dose rate per unit contained activity in a medium at 1 cm in water and air-kerma strength per unit contained activity for each seed model were calculated, allowing the dose rate constant (DRC) A to be estimated. The influence of the calibration procedure on source strength for low-energy brachytherapy seeds is discussed. Conversion factors for 125I and 103Pd seeds to obtain the dose rate in liquid water from the dose rate measured in a solid water phantom with a detector calibrated for dose to water were calculated. A theoretical estimate of the DRC for a 103Pd model 200 seed equal to 0.669 +/- 0.002 cGy h(-1) U(-1) is obtained. Comparison of obtained DRCs with measured and calculated published results shows agreement within 1.5% for 192Ir, 169Yb and 125I sources.
Assuntos
Braquiterapia/métodos , Fenômenos Biofísicos , Biofísica , Braquiterapia/estatística & dados numéricos , Humanos , Radioisótopos do Iodo/uso terapêutico , Radioisótopos de Irídio/uso terapêutico , Método de Monte Carlo , Paládio/uso terapêutico , Imagens de Fantasmas , Radioisótopos/uso terapêutico , Radiometria/estatística & dados numéricos , Dosagem Radioterapêutica , Espalhamento de Radiação , Tecnologia Radiológica , Água , Itérbio/uso terapêuticoRESUMO
Uma câmara de ionização de 23 cm3 com ar comprimido e parede de alumínio foi construída e apresenta sensibilidade uma ordem de grandeza maior quando comparada a câmaras de mesmo volume à pressão ambiente. A utilização de ar a uma pressão 2500 KPa minimiza sua dependência energética que se mantém menor que 5 por cento para energias de fótons na faixa de 40 KeV a 1.250 KeV. Esta câmara apresenta melhor desempenho do que as câmaras convencionais em medidas de baixas taxas de exposição.
Assuntos
Radiometria/estatística & dados numéricos , Dosimetria , Alumínio , Ionização do Ar/efeitos da radiação , Calibragem , Cobalto/efeitos da radiação , Raios gamaRESUMO
A histopathological and morphometric study was performed in the bone marrow of mice after association of cisdiamminedi-choroplatinum II (3.0 mg/kg) plus X-rays (103.20 mC/Kg 400R). Rstimation of bone marrow effects was assessed by counting the number of non nucleated-erythrocytes (NN) and nucleated (N) cells, and establishing (NN/N) ratio. The morphomeric method used correlates and makes possible quantification of histopathologic changes of bone marrow through relation of vascular stroma and cellular parenchyma. It can be used as a biological dosimetry parameter and to estimate injury and recovery of hematologic evolution of different myelotoxic agents