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The 18F F-labeled fluoro-2-deoxyglucose (18F-FDG) is the most widely used cyclotron-generated positron-emitting radiopharmaceutical in the clinical applications of PET scans. The production of radiopharmaceuticals such as 18F-FDG always presents internal contamination risks for the occupationally exposed workers. It is important to perform Individual monitoring on workers in case of incorporation or routinely. Usually, the calibration of these internal monitoring systems is performed using physical phantoms. This work aims to present the development of a physical head phantom for the calibration of an 18F-FDG in vivo internal monitoring system. Two materials, M1 and M2, composed of water, agar, and urea were proposed for the solid brain equivalent tissue. These materials presented the required characteristics of a brain equivalent tissue for the physical phantom construction in terms of morphology, material distribution, radiation attenuation, consistency, availability and low cost. Computational studies were performed to evaluate the effectiveness of the proposed materials. The calibration coefficients obtained for physical head phantom produced with material M2 and a known activity of 18F-FDG showed a good correlation with Monte Carlo results.

A atividade mínima detectável (AMD) representa o valor mínimo de atividade que é detectada em um sistema de monotoração. Existem diversas metodologias que podem ser utilizadas para calcular a AMD, no entanto os resultados para cada uma destas podem ser divergentes. Laboratórios de dosimetria interna in vivo devem dispor deste parâmetro para cada tipo de geometria de contagem, bem como, para cada tipo de radionuclídeo de interesse, visando a otimização do processo de monitoração interna. O objetivo deste trabalho foi comparar três tipos de metodologias de cálculo utilizadas na determinação da AMD com os resultados obtidos experimentalmente. As metodologias de cálculo utilizadas foram as sugeridas por Currie (1968), a publicada em Health Physics Society N13.30 (1996) e a ISO 11929 (2018). A monitoração de um phantom de cabeça contendo na região correspondente ao cérebro 18F-FDG foi realizada para a obtenção da AMD experimental. Os resultados obtidos para os valores de AMDs utilizando as três diferentes metodologias apresentaram diferenças de acordo com as faixas de atividades analisadas. As incertezas do fator de calibração e Background do sistema são os principais parâmetros entre as três metodologias de cálculo que influenciaram nos resultados obtidos.

The objective of this work is to present the results for quality control tests applied to projection images acquisition in digital mammography and breast tomosynthesis (DBT). Mean glandular doses (MGD) were measured for the examination of series of women and for breast-simulating polymethyl methacrylate phantoms, thus assessing the suitability of the phantoms used for dosimetry in 2D mammography for DBT dosimetry. Moreover, X-ray tube output and half value layer measurements for MGD estimation using phantoms are also presented. Three different mammography/DBT systems were considered in this work: Hologic Selenia Dimensions, General Electric Senoclaire and Pristina and Siemens Inspiration. The results obtained for the different projections were compared with the 2D acquisitions and the differences between the two image modalities were compared.

The aim of this study was to verify the availability of CT scanners in the Brazilian territory, for the period 2010 to 2017, comparing the results with those indicated by the Brazilian legislation (Ordinance GM/MS Nº. 1101, 2002; Resolution RE Nº. 1016, 2006). The second objective is a review of the most recent national data; publishing official statistics on the number of CT scanners installed in Brazil and compares them with the data available from other countries, obtained in international publications. Estimates of the CT scanners distribution are made by the utilization rate, which means the number of scans performed per thousand inhabitants multiplied by the total population of the region, where as the maximum coverage area of scanner in a radius of 75 km or 100,000 inhabitants. The results suggest greater concentration of equipment in the Southeast, South and Midwest area, private and public sectors, and a number of scans far above the recommended, throughout the Brazilian territory. The number of CT scanners currently in operation in Brazil would have the ability to cater to a population up to 110,7 % higher than the current population, and their geographical distribution within the country largely unknown.

As CT exams impart high doses to patients in comparison to other radiologist techniques, reliable dosimetry is required. In this work, dosimetry in CT beams was carried out in terms of air kerma index in air or in a phantom measured by a pencil ionization chamber, thermoluminescent (TL) detectors and radiochromic film. Calibration results showed the low energy dependence of all three dosimetric systems for the 100-120kV range, the very high uncertainty of the TL dosimeters in comparison to the other systems and high nonlinearity response in terms of air kerma of the radiochromic film. Measurements with the three systems in a 120kV CT protocol showed an acceptable agreement among the weighted air kerma index values, but TL dosimeters presented the highest uncertainties in the values.

Patient dose monitoring for different radiographic procedures has been used as a parameter to evaluate the performance of radiology services; skin entrance absorbed dose values for each type of examination were internationally established and recommended aiming patient protection. In this work, a methodology for dose evaluation was applied to three diagnostic services: one with a conventional film and two with digital computerized radiography processing techniques. The x-ray beam parameters were selected and “doses” (specifically the entrance surface and incident air kerma) were evaluated based on images approved in European criteria during postero-anterior (PA) and lateral (LAT) incidences. Data were collected from 200 patients related to 200 PA and 100 LAT incidences. Results showed that doses distributions in the three diagnostic services were very different; the best relation between dose and image quality was found in the institution with the chemical film processing. This work contributed for disseminating the radiation protection culture by emphasizing the need of a continuous dose reduction without losing the quality of the diagnostic image.

The Laboratory of Internal Dosimetry of the Center for Development of Nuclear Technology (LDI/CDTN) is responsible for routine internal monitoring of occupationally exposed individuals. The determination of photon emitting radionuclides in the human body requires calibration of the detector in specific counting geometries. The calibration process uses physical phantoms containing certified activities of the radionuclides of interest. The objective of this work was to obtain calibration efficiency curves of the Whole Body Counter in operation at the LDI/CDTN using a BOMAB physical phantom and Monte Carlo simulations.

This study determined the interaction of radiation parameters of four biomaterials as attenuators to measure the transmitted X-rays spectra, the mass attenuation coefficient and the effective atomic number by spectrometric system comprising the CdTe detector. The biomaterial BioOss® presented smaller mean energy than the other biomaterials. The μ/ρ and Zeff of the biomaterials showed their dependence on photon energy. The data obtained from analytical methods of x-ray spectra, µ/ρ and Zeff, using biomaterials as attenuators, demonstrated that these materials could be used as substitutes for dentin, enamel and bone. Further, they are determinants for the characterization of the radiation in tissues or equivalent materials.

Digital technology in mammography and breast tomosynthesis introduced the use of W and Rh target x-ray tubes with Al, Mo, Rh and Ag additional filters. In Brazil, due to the limited capability of metrology laboratories, x-ray dosimetry in mammography is done with different types of dosimeters that may not be calibrated for such specific clinical beams. The objective of this work was to study the influence of different calibration conditions on the determination of the mean glandular dose in dosimetry in mammography beams.

The reduction of the dose limit for the eye lenses of occupational exposed workers drew the attention of authorities to review the monitoring, the calibration method and the performance of the individual dosimeters. Calibration laboratories are expected to perform dosimeter calibrations and tests in standardized and reliable conditions. In this work, the 90Sr/90Y beta radiation beam of the Beta Secondary Standard system was characterized. Beam standardization was achieved by measuring the absorbed dose rate at 3 mm in tissue, ?T(3). A reliable procedure for calibrating eye lens dosimeters in terms of Hp(3) in the 90Sr/90Y beta radiation field was established.

Electronic dosimeters are widely used for individual monitoring, especially for direct dose equivalent assessment associated with a specific task. Most of x-ray beams used in diagnostic radiology have been considered as pulsed one due to their high intensity during a very short time. This work showed that a Rhos Vari X x-ray machine was feasible to be used to evaluate electronic dosimeters in high pulsed air kerma rates to detect deficiencies in their response. In comparison to continuous x-ray beams, it was observed that personal dose equivalent values were severely underestimated by some electronic dosimeters in pulsed radiation fields.

During a lung computed tomography (CT) examination, breast and nearby radiosensitive organs are unnecessarily irradiated because they are in the path of the primary beam. The purpose of this paper is to determine the absorbed dose in breast and nearby organs for unshielded and shielded exposures with bismuth. The experiment was done with a female anthropomorphic phantom undergoing a typical thoracic CT scan, with TLD-100 thermoluminescent detectors insert at breast, lung and thyroid positions. Results showed that dose reduction due to bismuth shielding was approximately 30% and 50% for breast and thyroid, respectively; however, the influence of the bismuth on the image quality needs to be considered.

Objetivo: O objetivo deste trabalho é avaliar a dose em pacientes submetidos a PET/CT para diagnóstico de comprometimento cognitivo leve. Materiais e Métodos: Para as medidas da dose absorvida proveniente da modalidade CT utilizaram-se detectores TLD-100 inseridos em um simulador Alderson Rando®. Os simuladores antropomórficos (versões masculina e feminina) foram submetidos aos mesmos protocolos técnicos para aquisição das imagens dos pacientes. A dose absorvida resultante da injeção do radiofármaco foi estimada por meio do modelo proposto pela ICRP 106. Resultados: A dose efetiva a que foram submetidos os pacientes com esta técnica diagnóstica foi, aproximadamente, (5,34 ± 1,99) mSv. Conclusão: Protocolos otimizados para cálculo de atividade radioativa que será injetada em cada paciente podem contribuir para a redução da dose efetiva nos pacientes durante a realização do diagnóstico de comprometimento cognitivo leve com PET/CT. Objective: The present study was aimed at evaluating the effective radiation dose in patients submitted to PET/CT for the diagnosis of mild cognitive impairment. Materials and Methods: TLD-100 detectors inserted into an Alderson Rando® anthropomorphic phantom were utilized to measure the absorbed dose coming from the CT imaging modality. The anthropomorphic phantoms (male and female adult versions) were submitted to the same technical protocols for patients’ images acquisition. The absorbed dose resulting from the radiopharmaceutical injection was estimated by means of the model proposed by the ICRP publication 106. Results: The effective dose in patients submitted to this diagnostic technique was approximately (5.34 ± 1.99) mSv. Conclusion: Optimized protocols for calculation of radioactive activity injected into patients submitted to this diagnostic technique might contribute to reduce the effective radiation dose resulting from PET/CT in the diagnosis of mild cognitive impairment.

The Laboratory of Internal Dosimetry of the Center for Development of Nuclear Technology (LDI/CDTN) is responsible for routine monitoring of internal contamination of the Individuals Occupationally Exposed (IOEs) at the Unit for Research and Production of Radiopharmaceuticals (UPPR/CDTN), the Research Reactor TRIGA-IPR-R1/CDTN and other workplaces of the institute where there is a risk of accidental intakes. Additionally, LDI supports the Institute of Radiation Protection and Dosimetry (IRD/CNEN) to attend radiological emergencies. The determination of photon emitting radionuclides in the human body requires the use of calibration techniques in different counting geometries for converting the count rates into activity in organs and tissues. This paper presents and discusses the calibration of the LDI/CDTN Whole Body Counter (WBC) using a standard BOMAB phantom (Bottle Mannequin Absorber) compared to a home-made phantom produced with Polyethylene Terephthalate bottles (PET). Initially, the BOMAB was filled with a cocktail containing 60 Co, 137 Cs and 133 Ba. The phantom was counted at the LDI whole body counter and an Efficiency x Energy curve was obtained. Subsequently the PET-BOMAB was filled with the same standard source and a second curve was determined. The efficiency values in each region of interest as well as the shape of both curves were found to be equivalent. The results validate the use of the PET-BOMAB for the calibration of whole body geometry applied to the measurement of high energy radionuclides in the energy region evaluated in this work.

Electronic personal dosimeters (EPD) based on solid state detectors have been used for personnel monitoring for radiation protection purpose; their use has been extended to practices with pulsed radiation beams although their performance is not well known. Deficiencies in the EPD response in pulsed radiation fields have been reported; they were not detected before since type tests and calibrations of EPDs were established in terms of continuous X and gamma reference radiations. An ISO working group was formed to elaborate a standard for test conditions and performance requirements of EPDs in pulsed beams; the PTB/Germany implemented a special X-ray facility for generating the reference pulsed radiation beams. In this work, an 800 Plus VMI medical X-ray machine of the Dosimeter Calibration Laboratory of CDTN/CNEN was characterized to verify its feasibility to perform EPD tests. Characterization of the x-ray beam was done in terms of practical peak voltage, half-value layer, mean energy and air kerma rate. Reference dosimeters used for air kerma measurements were verified as far their metrological coherence and a procedure for testing EDPs was established.

OBJETIVO: Verificar a viabilidade de filmes radiocrômicos como um dosímetro alternativo para estimativa da dose média em cortes múltiplos a partir dos perfis de kerma. MATERIAIS E MÉTODOS: Os filmes foram distribuídos em cilindros posicionados no centro e nas regiões periféricas de um objeto simulador padrão de abdome utilizado para dosimetria em tomografia computadorizada. RESULTADOS: Os valores de dose média em cortes múltiplos calculados foram 13,6 ± 0,7, 13,5 ± 0,7 e 18,7 ± 1,0 mGy para os valores de passo (pitch) de 0,75, 1,00 e 1,50, respectivamente. CONCLUSÃO: Apesar de os resultados mostrarem valores menores que o nível de referência de radiodiagnóstico de 25 mGy estabelecido pela legislação brasileira para exames de abdome, eles sugerem que há espaço para otimização dos procedimentos e uma revisão do valor para o nível de referência de radiodiagnóstico brasileiro.OBJECTIVE: To evaluate the feasibility of using radiochromic films as an alternative dosimeter to estimate the multiple scan average dose on the basis on kerma profiles. MATERIALS AND METHODS: The radiochromic films were distributed in cylinders positioned in the center and in four peripheral bores of a standard abdominal phantom utilized for computed tomography dosimetry. RESULTS: Values for multiple scan average dose values corresponded to 13.6 ± 0.7, 13.5 ± 0.7 and 18.7 ± 1.0 mGy for pitch of 0.75, 1.00 and 1.50, respectively. CONCLUSION: In spite of results showing lower values than the reference level for radiodiagnosis (25 mGy) established by the Brazilian regulations for abdominal studies, it is suggested that there is room to optimize procedures and review the reference level for radiodiagnosis in Brazil.

OBJETIVO: Verificar a viabilidade de filmes radiocrômicos como um dosímetro alternativo para estimativa da dose média em cortes múltiplos a partir dos perfis de kerma. MATERIAIS E MÉTODOS: Os filmes foram distribuídos em cilindros posicionados no centro e nas regiões periféricas de um objeto simulador padrão de abdome utilizado para dosimetria em tomografia computadorizada. RESULTADOS: Os valores de dose média em cortes múltiplos calculados foram 13,6 ± 0,7, 13,5 ± 0,7 e 18,7 ± 1,0 mGy para os valores de passo (pitch) de 0,75, 1,00 e 1,50, respectivamente. CONCLUSÃO: Apesar de os resultados mostrarem valores menores que o nível de referência de radiodiagnóstico de 25 mGy estabelecido pela legislação brasileira para exames de abdome, eles sugerem que há espaço para otimização dos procedimentos e uma revisão do valor para o nível de referência de radiodiagnóstico brasileiro.

A new regulatory statement was issued concerning the eye lens radiation protection of persons in planned exposures. A debate was raised on the adequacy of the dosimetric quantity and on its method of measurement. The aim of this work was to establish the individual monitoring procedure with the EYE-D™ holder and a MCP-N LiF:Mg,Cu,P thermoluminescent chip detector for measuring the personal dose equivalent Hp(3) in workers of a Positron Emission Tomography Radiopharmaceutical Production Facility.

Dosimetric studies in patients submitted to diagnostic radiology examinations have been done in Brazil with the aim of contributing to a radiation protection culture. In this work, a typical chest examination condition was simulated and absorbed doses in selected organs were measured with thermoluminescent dosimeters in a Rando-Alderson anthropomorphic phantom. Doses were also calculated with PCXMC ® and CALDose_X Monte Carlo based softwares. In most cases, organ absorbed doses calculated by Caldose_X agreed up to 50% with values from the reliable experimental procedure based on TL dosimeters in the Rando-Alderson phantom. PCXMC ® calculations showed large differences in organ absorbed doses that could not be explained. Lack of agreement among doses obtained with the three adopted methodologies could be attributed to the differences between their phantoms in terms size, weight and location of organs as well as poor representation of human anatomy. If a large survey of dose assessment in patients submitted to chest X-ray examinations is intended to be done, the results of this work should be considered.

The present study determined the organic and inorganic composition of human enamel and dentin. The instrumental neutron activation analysis, inductively-coupled plasma spectrometer, thermogravimetric and differential thermal analysis and X-ray diffraction analysis applied were and performed in the Nuclear Technology Development Centre (CDTN) and Elemental Analysis in the Department of Chemistry of the Federal University of Pernambuco, Brazil. The coronal dentin and enamel were separated from dentin mechanically (1) and by wear (2). The analyses were effective and led to the identification of the main elements present in enamel and dentin: Ca, Na, Cl, Zn, P, Mg, N, C, H, O. There was no contamination of samples of enamel or dentin in either separation technique; however, with separation technique 1, lower percentages of mainly Ca (7.25%) and O (15.16%) components were detected in dentin compared with technique 2.

Objective: The aim of this human study was to evaluate the radiation doses in the buccal cavity and face, during panoramic, spiral conventional tomography, and helicoidal computerized tomography exams. Material and Methods: Lithium fluoride TL detectors (TLD-100) were placed on the skin at anatomic points such as parotid glands, submandibular glands, thyroid glands, and crystalline to assess the skin entrance dose in 19 patients who were to undergo dental implant surgery. Results: In the panoramic exam, maximum doses were observed near the parotid glands at 1.57 (±18%) mGy on the right and 1.89 (±18%) mGy on the left. In the spiral conventional tomography exam, the maximum dose was 4.41 (±21%) mGy near the right and left parotid glands, whereas near the right or left submandibular glands, the maximum doses reached 40.7 (±18%) mGy. In the helicoidal computerized tomography for mandibular and maxilla exams, the maximum dose was 40.9 (±15%) mGy near the parotid glands and 41.0 (±18%) mGy near the submandibular glands. Near the thyroid and eye lens, doses were lower than 0.23 (±21%) in all exams. Conclusion: Regardless of the exam target area, the submandibular and parotid glands represented the most irradiated organs. This data suggests that efforts should be made by professionals to improve and optimize methods in order to reduce doses without losing the information necessary for treatment planning.

OBJETIVO: Os objetivos deste trabalho são: a) avaliar os procedimentos radiográficos e estimar o valor do kerma no ar na superfície de entrada nos recém-nascidos prematuros submetidos a exames de tórax e abdome, realizados no setor de neonatologia de um hospital público de Belo Horizonte; b) estimar as doses nos órgãos e os respectivos riscos de ocorrência de câncer nesses órgãos em decorrência das exposições à radiação. MATERIAIS E MÉTODOS: Foram analisados os prontuários dos pacientes internados no setor de neonatologia desse hospital durante o período de maio a setembro de 2004, anotando-se os dados antropométricos, data de internação/alta, exames de raios X realizados. O kerma no ar na superfície de entrada foi determinado a partir do rendimento do tubo de raios X e dos parâmetros de irradiação utilizados nos exames. As doses nos órgãos foram estimadas com o software PCXMC e o risco, durante o restante da expectativa de vida, com o software IREP. RESULTADOS: O valor médio do kerma no ar na superfície de entrada por exame foi abaixo do nível de referência da publicação da Comunidade Européia. Para o paciente mais severamente irradiado, os órgãos mais suscetíveis à ocorrência de câncer foram fígado, mama e estômago, com valores máximos de excess relative risk, respectivamente, de 3,4%, 2,3% e 1,7%. CONCLUSÃO: Foi constatada a necessidade de otimização dos procedimentos radiográficos com vista à diminuição do risco para os recém-nascidos, que apesar de ser considerado baixo (comparativamente ao benefício), deve ser sempre diminuído para valores tão baixos quanto razoavelmente exeqüíveis.OBJECTIVE: The present study was aimed at: a) evaluating radiographic procedures and estimating entrance surface air kerma in preterm neonates submitted to chest and abdominal radiography at the unit of neonatology in a public hospital of Belo Horizonte, MG, Brazil; b) estimating the dose to organs and respective risks for cancer as a result from radiation exposure. MATERIALS AND METHODS: Records of patients admitted to the unit of neonatology of this hospital in the period between May and September 2004 were reviewed. Anthropometric data, admission/discharge dates and radiographic studies performed were recorded for each of the patients. The calculation of the entrance surface air kerma was based on the x-ray tube output and irradiation parameters adopted for examinations. Dose to organs was calculated with the aid of the software PCXMC, and the lifetime risk for cancer, with the software IREP. RESULTS: Mean entrance surface air kerma per examination was below the diagnostic reference levels recommended by the European Community. In the most severely irradiated patients, liver, breast and stomach were the organs at highest risk for cancer, with maximum excess relative risk of respectively 3.4%, 2.3%, and 1.7%. CONCLUSION: The present study demonstrated the need for optimization of radiographic procedures in order to reduce the risks for neonates that, in spite of being considered to be low as compared with the benefits, should be reduced to values as low as reasonably achievable.

OBJETIVO: Os objetivos deste trabalho são: a) avaliar os procedimentos radiográficos e estimar o valor do kerma no ar na superfície de entrada nos recém-nascidos prematuros submetidos a exames de tórax e abdome, realizados no setor de neonatologia de um hospital público de Belo Horizonte; b) estimar as doses nos órgãos e os respectivos riscos de ocorrência de câncer nesses órgãos em decorrência das exposições à radiação. MATERIAIS E MÉTODOS: Foram analisados os prontuários dos pacientes internados no setor de neonatologia desse hospital durante o período de maio a setembro de 2004, anotando-se os dados antropométricos, data de internação/alta, exames de raios X realizados. O kerma no ar na superfície de entrada foi determinado a partir do rendimento do tubo de raios X e dos parâmetros de irradiação utilizados nos exames. As doses nos órgãos foram estimadas com o software PCXMC e o risco, durante o restante da expectativa de vida, com o software IREP. RESULTADOS: O valor médio do kerma no ar na superfície de entrada por exame foi abaixo do nível de referência da publicação da Comunidade Européia. Para o paciente mais severamente irradiado, os órgãos mais suscetíveis à ocorrência de câncer foram fígado, mama e estômago, com valores máximos de excess relative risk, respectivamente, de 3,4%, 2,3% e 1,7%. CONCLUSÃO: Foi constatada a necessidade de otimização dos procedimentos radiográficos com vista à diminuição do risco para os recém-nascidos, que apesar de ser considerado baixo (comparativamente ao benefício), deve ser sempre diminuído para valores tão baixos quanto razoavelmente exeqüíveis. OBJECTIVE: The present study was aimed at: a) evaluating radiographic procedures and estimating entrance surface air kerma in preterm neonates submitted to chest and abdominal radiography at the unit of neonatology in a public hospital of Belo Horizonte, MG, Brazil; b) estimating the dose to organs and respective risks for cancer as a result from radiation exposure. MATERIALS AND METHODS: Records of patients admitted to the unit of neonatology of this hospital in the period between May and September 2004 were reviewed. Anthropometric data, admission/discharge dates and radiographic studies performed were recorded for each of the patients. The calculation of the entrance surface air kerma was based on the x-ray tube output and irradiation parameters adopted for examinations. Dose to organs was calculated with the aid of the software PCXMC, and the lifetime risk for cancer, with the software IREP. RESULTS: Mean entrance surface air kerma per examination was below the diagnostic reference levels recommended by the European Community. In the most severely irradiated patients, liver, breast and stomach were the organs at highest risk for cancer, with maximum excess relative risk of respectively 3.4%, 2.3%, and 1.7%. CONCLUSION: The present study demonstrated the need for optimization of radiographic procedures in order to reduce the risks for neonates that, in spite of being considered to be low as compared with the benefits, should be reduced to values as low as reasonably achievable.

The introduction of routine patient dosimetry to Brazilian radiological institutions is very necessary in order to meet national and international standard requirements for radiation protection. This work presents a survey of the air kerma-area product (P(KA)), the entrance surface air kerma (K(e)) and the effective dose (E) in common radiographic examinations during the routine of a large public hospital in the city of Belo Horizonte, Brazil. Results draw attention to the use of field sizes larger than the cassette dimension, the lack of both the collimation X-ray beam and the standardisation of the exposure parameters by radiology technicians.

Medical staff during interventional radiology could be exposed to radiation conditions that may cause very high dose levels depending on the X-ray machine operational conditions. The dose levels received by medical staff during interventional radiology are very high depending on the operational conditions and the patient trunk thickness. Dose levels could reach a factor of 30 for fluoroscopy or cine modes. The ALARA principle, which emphasizes the adoption of techniques and procedures to keep dose levels as low as reasonably achievable, should be followed to minimize the risk of radiation exposure to medical professionals. Dose reduction could be achieved by persuading the medical staff to wear protection devices (lead apron, thyroid protector, eyeglasses and gloves). Additionally, medical staff should also be persuaded that they should not be submitted to very high doses, above the acceptable limits for occupational workers. Dose levels at hemodynamics services in Minas Gerais State, Brazil, were analyzed. Due to the equipment characteristics or the exam type and conditions X-ray machines were used with 70–120 kV, 2.5–699 mA and 80–2880 s. Annual individual doses were estimated based on measured doses during a specific exam taking into account the workload. Maximum doses varied from 0.05 to 0.70 mSv per exam. The results projected for one work-year period show that all annual individual doses would be higher than the annual dose limit of 20 mSv/y with only a few values lower than 50 mSv/y. Dose levels measured at medical staff positions during hemodynamic exams showed that if the protective devices are not used professionals could be exposed to dose values higher than annual dose limits.

OBJETIVO: Avaliar a freqüência das incidências radiográficas realizadas nos seios da face de pacientes pediátricos em hospitais de Belo Horizonte, MG, as condições de radioproteção, as técnicas radiográficas empregadas, o kerma no ar de entrada e as doses nos órgãos mais expostos. MATERIAIS E MÉTODOS: Foram coletados os dados dos pacientes e parâmetros de técnica radiográfica empregados em exames de crianças de 1 a 16 anos de idade, em cinco salas de quatro hospitais da cidade, observando, também, aspectos de proteção radiológica. O kerma no ar de entrada foi estimado a partir dos rendimentos dos tubos de raios-x e as doses nos órgãos utilizando o software PCXMC. RESULTADOS: Os valores médios do kerma no ar de entrada para as cinco salas foram, respectivamente, 1.398 µGy, 829 µGy, 877 µGy, 1.168 µGy e 3.886 µGy para pacientes entre 1 e 5 anos de idade. CONCLUSÃO: Foi constatado que as incidências mento-naso e fronto-naso são comumente solicitadas em conjunto, na maioria dos hospitais, o que confere dose significativa para os pacientes. Os riscos para os pacientes podem ser diminuídos mediante a utilização de cilindros de colimação, a não-utilização de grades antiespalhamento, o emprego de altos valores de tensão e baixos valores de tempo.OBJECTIVE: The present study was aimed at evaluating the frequency of radiographic assessment of paranasal sinuses in pediatric patients in hospitals of Belo Horizonte, MG, Brazil. Additionally, aspects regarding radiation protection conditions and radiographic parameters were evaluated, and entrance air kerma and organ doses were estimated. MATERIALS AND METHODS: Patients' data and parameters of radiographic technique employed in the assessment of children in the age range between 1 and 16 years were collected in five examination rooms of four hospitals in Belo Horizonte, also taking into consideration the radiation protection aspects. Entrance air kerma calculation was based on the x-ray tubes output, and organ doses were estimated with the PCXMC software. RESULTS: Mean entrance air kerma values found in the five rooms were, respectively, 1398 µGy, 829 µGy, 877 µGy, 1168 µGy and 3886 µGy for patients with ages between 1 and 5 years. CONCLUSION: Most frequently, mento-naso and fronto-naso views are requested in conjunction in the majority of hospitals, which increases the radiation dose to the patients. It may be concluded that the risks for patients can be reduced by means of the utilization of an appropriate x-ray field, non-utilization of antiscattering grids, selection of high voltages and lower exposure times.

OBJETIVO: A análise crítica da metodologia de medida da camada semi-redutora em feixes de raios X teve como base o regulamento técnico para proteção radiológica e controle de qualidade em radiodiagnóstico médico e odontológico. MATERIAIS E MÉTODOS: Na medida da camada semi-redutora, a técnica radiográfica, o arranjo experimental, os meios espalhadores, a instrumentação, o tamanho de campo de radiação e a metodologia de análise dos dados foram considerados. RESULTADOS: A camada semi-redutora obtida em condições de boa geometria, para a técnica escolhida, foi de 2,44 ± 0,02 mmAl. Em relação a este valor, observaram-se desvios máximos na camada semi-redutora de 4,1% na variação da geometria, de 98,8% na variação da câmara de ionização e do meio espalhador, e de até 29,5% com outro tipo de detector. CONCLUSÃO: Os resultados mostraram que não ocorre variação significante na camada semi-redutora para diferentes tamanhos de campo de radiação, mas foram evidentes a influência do espalhamento na superestimação da camada semi-redutora e a redução desta na presença de blocos de chumbo como meio espalhador. O procedimento prático adotado mostrou-se bastante confiável e evidenciou a grande discrepância decorrente da adoção de metodologias impróprias, enfatizando a necessidade de estabelecer um procedimento padrão para a medida da camada semi-redutora.OBJECTIVE: The critical analysis of the methodology for evaluating the x-ray beam half-value layer was based on technical standards for radiological protection and quality control in medical and dental diagnoses. MATERIALS AND METHODS: Exposure parameters, experimental set-up, scattering materials, instrumentation, size of radiation field and methodology of data analysis have been taken into consideration for measurements of half-value layer. RESULTS: The half-value layer, in good geometry, measured 2.44 ± 0.02 mmAl. A maximum deviation of 4.1% was found under other geometry conditions. A 98.8% deviation was observed with a different ionization chamber, and scattering material, and 29.5% with another type of detector. CONCLUSION: Results showed that no relevant variation is observed in the half-value layer for different radiation field sizes. On the other hand, the influence of the radiation scattering on the half-value layer overestimation was clearly observed, as well as the half-value layer reduction in the presence of lead used as scattering material. The practical methodology adopted for half-value layer evaluation has shown to be quite reliable, besides evidencing remarkable discrepancies resulting from the adoption of inappropriate methodologies, emphasizing the necessity of establishing a standard procedure for measuring the half-value layer.

OBJETIVO: A análise crítica da metodologia de medida da camada semi-redutora em feixes de raios X teve como base o regulamento técnico para proteção radiológica e controle de qualidade em radiodiagnóstico médico e odontológico. MATERIAIS E MÉTODOS: Na medida da camada semi-redutora, a técnica radiográfica, o arranjo experimental, os meios espalhadores, a instrumentação, o tamanho de campo de radiação e a metodologia de análise dos dados foram considerados. RESULTADOS: A camada semi-redutora obtida em condições de boa geometria, para a técnica escolhida, foi de 2,44 ± 0,02 mmAl. Em relação a este valor, observaram-se desvios máximos na camada semi-redutora de 4,1% na variação da geometria, de 98,8% na variação da câmara de ionização e do meio espalhador, e de até 29,5% com outro tipo de detector. CONCLUSÃO: Os resultados mostraram que não ocorre variação significante na camada semi-redutora para diferentes tamanhos de campo de radiação, mas foram evidentes a influência do espalhamento na superestimação da camada semi-redutora e a redução desta na presença de blocos de chumbo como meio espalhador. O procedimento prático adotado mostrou-se bastante confiável e evidenciou a grande discrepância decorrente da adoção de metodologias impróprias, enfatizando a necessidade de estabelecer um procedimento padrão para a medida da camada semi-redutora. OBJECTIVE: The critical analysis of the methodology for evaluating the x-ray beam half-value layer was based on technical standards for radiological protection and quality control in medical and dental diagnoses. MATERIALS AND METHODS: Exposure parameters, experimental set-up, scattering materials, instrumentation, size of radiation field and methodology of data analysis have been taken into consideration for measurements of half-value layer. RESULTS: The half-value layer, in good geometry, measured 2.44 ± 0.02 mmAl. A maximum deviation of 4.1% was found under other geometry conditions. A 98.8% deviation was observed with a different ionization chamber, and scattering material, and 29.5% with another type of detector. CONCLUSION: Results showed that no relevant variation is observed in the half-value layer for different radiation field sizes. On the other hand, the influence of the radiation scattering on the half-value layer overestimation was clearly observed, as well as the half-value layer reduction in the presence of lead used as scattering material. The practical methodology adopted for half-value layer evaluation has shown to be quite reliable, besides evidencing remarkable discrepancies resulting from the adoption of inappropriate methodologies, emphasizing the necessity of establishing a standard procedure for measuring the half-value layer.

This study determined the interaction of radiation parameters of four biomaterials as attenuators to measure the transmitted X-rays spectra, the mass attenuation coefficient and the effective atomic number by spectrometric system comprising the CdTe detector. The biomaterial BioOss

Dosimetros eletronicos, pela praticidade de leitura direta, tem sido cada vez mais utilizados para monitoracao individual ou de area para fins de radioprotecao em campos de raios X usados em radiologia diagnostica. Deficiencias no desempenho de tais dosimetros em feixes pulsados tem sido publicadas, que nao sao detectadas pelos procedimentos de calibracao e testes de desempenho estabelecidos por normas internacionais somente para feixes continuos de radiacao. No Brasil, nao ha requisitos de desempenho de dosimetros em feixes pulsados, nem um laboratorio que realize ensaios para maior confiabilidade no uso dos dosimetros. Este trabalho objetiva caracterizar a maquina de raios X medico VMI 800 Plus no Laboratorio de Calibracao de Dosimetros do CDTN/CNEN e estudar a viabilidade da sua utilizacao para testes de desempenho de dosimetros eletronicos.

In diagnostic radiology, the radiation interaction probability in matter is a strong function of the X-ray energy. The knowledge of the X-ray energy spectral distribution allows optimizing the radiographic imaging system in order to obtain high quality images with as low as reasonably achievable patient doses. In this study, transmitted X-ray spectra through dentin and enamel that are existing materials in intra-oral radiology were experimentally determined in an X-ray equipment with 40–70 kV variable range. Dentin and enamel samples with 0.4–3.8 and 0.6–2.6 mm thick were used as attenuators. X-ray transmitted spectra were measured with XR-100T model CdTe detector and half-value layers (HVL) were determined. Characteristics of both dentin and enamel transmitted spectra showed that they have differences in the penetration power in matter and in the spectrum distribution. The results will be useful for phantom developments based on dentin and enamel for image quality control in dental radiology.

Objetivo: Visando contribuir para o conhecimento das doses em tomografia computadorizada (TC), este trabalho teve o objetivo de quantificar grandezas dosimétricas associadas a exames do abdome em pacientes pediátricos, comparando-as com os níveis de referência em radiodiagnóstico (NRD). Materiais e métodos: O estudo foi realizado em dois hospitais, em um tomógrafo Toshiba Asteion single-slice e um GE BrightSpeed multi-slice. Medidas foram feitas com uma câmara de ionização tipo lápis e um objeto simulador de tronco de polimetilmetacrilato de 16 cm de diâmetro. Resultados: Os valores do índice ponderado de kerma no ar (CW) não apresentaram diferenças significativas, porém, para as grandezas índice de kerma no ar volumétrico (CVOL), produto kerma-comprimento (PKL,CT) e dose efetiva, as diferenças foram relevantes. Conclusão: Apenas o CW apresentou valores menores que os NRD, sugerindo que a otimização não seria necessária. Porém, os valores de PKL,CT e dose efetiva mostraram que há espaço para reduzir as doses de radiação pediátricas. Este trabalho ressalta a importância de avaliar todas as grandezas dosimétricas associadas aos exames por TC. Objective: Aiming at contributing to the knowledge on doses in computed tomography (CT), this study has the objective of determining dosimetric quantities associated with pediatric abdominal CT scans, comparing the data with diagnostic reference levels (DRL). Materials and methods: The study was developed with a Toshiba Asteion single-slice CT scanner and a GE BrightSpeed multi-slice CT unit in two hospitals. Measurements were performed with a pencil-type ionization chamber and a 16 cm-diameter polymethylmethacrylate trunk phantom. Results: No significant difference was observed in the values for weighted air kerma index (CW), but the differences were relevant in values for volumetric air kerma index (CVOL), air kerma-length product (PKL,CT) and effective dose. Conclusion: Only the CW values were lower than the DRL, suggesting that dose optimization might not be necessary. However, PKL,CT and effective dose values stressed that there still is room for reducing pediatric radiation doses. The present study emphasizes the importance of determining all dosimetric quantities associated with CT scans.

Aiming at contributing to the knowledge on doses in computed tomography (CT), this study has the objective of determining dosimetric quantities associated with pediatric abdominal CT scans, comparing the data with diagnostic reference levels (DRL).The study was developed with a Toshiba Asteion single-slice CT scanner and a GE BrightSpeed multi-slice CT unit in two hospitals. Measurements were performed with a pencil-type ionization chamber and a 16 cm-diameter polymethylmethacrylate trunk phantom.No significant difference was observed in the values for weighted air kerma index (CW), but the differences were relevant in values for volumetric air kerma index (CVOL), air kerma-length product (PKL,CT) and effective dose.Only the CW values were lower than the DRL, suggesting that dose optimization might not be necessary. However, PKL,CT and effective dose values stressed that there still is room for reducing pediatric radiation doses. The present study emphasizes the importance of determining all dosimetric quantities associated with CT scans.Visando contribuir para o conhecimento das doses em tomografia computadorizada (TC), este trabalho teve o objetivo de quantificar grandezas dosimétricas associadas a exames do abdome em pacientes pediátricos, comparando-as com os níveis de referência em radiodiagnóstico (NRD).O estudo foi realizado em dois hospitais, em um tomógrafo Toshiba AsteionOs valores do índice ponderado de kerma no ar (CApenas o C

(18)FDG, an analogue of glucose labelled with the radionuclide (18)F, is the most widely used radiopharmaceutical in positron emission tomography/computed tomography technique. In Brazil, there are currently eight (18)FDG plants in operation and other facilities are expected to start their production in the near future. The growth in the production and clinical use of (18)FDG represents an increasing risk of worker exposures. According to national regulations and international recommendations, internal exposures should be effectively controlled in order to keep doses as low as possible. The implementation of a routine monitoring programme towards the estimation of internal doses related to the incorporation of (18)F is difficult, mainly due to its short physical half-life, the cost of a bioassay laboratory and the need of a monitoring service promptly available near the production plant. This paper describes the implementation and evaluation of a methodology for in vivo brain monitoring of (18)F to be applied in cases of suspected incorporation of (18)FDG. The technique presented a minimum detectable effective dose in the order of nanoSieverts, which allows its application for occupational monitoring purposes.

OBJETIVO: Avaliar a freqüência das incidências radiográficas realizadas nos seios da face de pacientes pediátricos em hospitais de Belo Horizonte, MG, as condições de radioproteção, as técnicas radiográficas empregadas, o kerma no ar de entrada e as doses nos órgãos mais expostos. MATERIAIS E MÉTODOS: Foram coletados os dados dos pacientes e parâmetros de técnica radiográfica empregados em exames de crianças de 1 a 16 anos de idade, em cinco salas de quatro hospitais da cidade, observando, também, aspectos de proteção radiológica. O kerma no ar de entrada foi estimado a partir dos rendimentos dos tubos de raios-x e as doses nos órgãos utilizando o software PCXMC. RESULTADOS: Os valores médios do kerma no ar de entrada para as cinco salas foram, respectivamente, 1.398 µGy, 829 µGy, 877 µGy, 1.168 µGy e 3.886 µGy para pacientes entre 1 e 5 anos de idade. CONCLUSÃO: Foi constatado que as incidências mento-naso e fronto-naso são comumente solicitadas em conjunto, na maioria dos hospitais, o que confere dose significativa para os pacientes. Os riscos para os pacientes podem ser diminuídos mediante a utilização de cilindros de colimação, a não-utilização de grades antiespalhamento, o emprego de altos valores de tensão e baixos valores de tempo. OBJECTIVE: The present study was aimed at evaluating the frequency of radiographic assessment of paranasal sinuses in pediatric patients in hospitals of Belo Horizonte, MG, Brazil. Additionally, aspects regarding radiation protection conditions and radiographic parameters were evaluated, and entrance air kerma and organ doses were estimated. MATERIALS AND METHODS: Patients' data and parameters of radiographic technique employed in the assessment of children in the age range between 1 and 16 years were collected in five examination rooms of four hospitals in Belo Horizonte, also taking into consideration the radiation protection aspects. Entrance air kerma calculation was based on the x-ray tubes output, and organ doses were estimated with the PCXMC software. RESULTS: Mean entrance air kerma values found in the five rooms were, respectively, 1398 µGy, 829 µGy, 877 µGy, 1168 µGy and 3886 µGy for patients with ages between 1 and 5 years. CONCLUSION: Most frequently, mento-naso and fronto-naso views are requested in conjunction in the majority of hospitals, which increases the radiation dose to the patients. It may be concluded that the risks for patients can be reduced by means of the utilization of an appropriate x-ray field, non-utilization of antiscattering grids, selection of high voltages and lower exposure times.

Uma das exigências na calibração de monitores de radiação de contaminação de superfície consiste no uso de fontes extensas de referência com um valor de uniformidade superior a 90%. Entretanto, foi verificado em alguns laboratórios de calibração que suas fontes não atendiam essa exigência, o que obrigaria esses laboratórios a não utilizarem tais fontes em suas calibrações. Foi neste contexto que foi desenvolvido um estudo para propor o uso dessas fontes, desde que sejam utilizados fatores de correção, que são propostos neste trabalho, que foram avaliados e desenvolvidos usando o código de transporte MCNP como ferramenta de análise e avaliação, a partir dos dados de mapeamento da uniformidade. Também foi desenvolvido um software para calcular esses fatores de correção, utilizando o mapeamento da uniformidade das fontes como dados de entrada e um sistema automatizado para calibração de monitores de radiação de contaminação de superfície. O grande ganho com esse trabalho foi poder utilizar fontes extensas de referência, mesmo quando essas estão em desacordo com as exigências de uniformidade da norma ABNT ISO 8769:2016. One of the requirements in the calibration of surface contamination radiation monitors is the use of wide area reference sources with a uniformity value greater than 90%. However, it has been found, in some calibration laboratories, that their sources were not meeting this requirement, which would not allow these laboratories to use such sources in their calibration procedures. It was in this context that a study was developed to propose the use of these sources, provided that correction factors are used, which are proposed in this work, which were evaluated and developed using the MCNP radiation transport code as an evaluation tool, from the uniformity mapping data. A software was also developed to calculate these correction factors using the source uniformity mapping as an input data along with an automated system for calibration of surface contamination radiation monitors. The great gain in this work was to be able to use wide area reference sources, even when they are in disagreement with the uniformity requirements of ISO 8769:2016.

A dose glandular média é a grandeza utilizada para dosimetria em mamografia. Esta grandeza apresenta grande dependência com propriedades específicas referentes ao tipo de mama a ser avaliada, tais como sua glandularidade e espessura comprimida. Depende também das propriedades do espectro de raios X, tais como a combinação anodo/filtro e a tensão aplicada ao tubo, que modificam a camada semirredutora do feixe. A caracterização do feixe de raios X através da medição direta do seu espectro é um procedimento de alta complexidade e de difícil execução em sistemas de mamografia, devido à arquitetura dos equipamentos e da alta taxa de fluência de fótons característica dos feixes. Estes espectros representam a fonte de informações quantitativas e qualitativas mais completa do feixe. O objetivo geral desse trabalho é estimar distribuições de dose glandular em diferentes profundidades de materiais simuladores de tecido mamário por meio de espectros de raios X medidos em mamógrafos. Para isso, foram utilizadas técnicas radiográficas comumente empregadas na mamografia para o rastreamento do câncer de mama. Foi avaliado o comportamento da dose glandular média normalizada pelo kerma no ar incidente (DgNp) com parâmetros relacionados à mama (glandularidade e espessura) e aos espectros (camada semirredutora, tensão, combinação alvo/filtro). Primeiramente, foi desenvolvida uma metodologia experimental para medição dos espectros de raios X nos mamógrafos. Em seguida, foram propostos os seguintes métodos de cálculo da DgNp utilizando esses espectros: Método I, que calcula a DgNp com espectros incidentes; Método II, que utiliza espectros incidentes e transmitidos para este cálculo e Método III, que usa espectros incidentes e transmitidos para estimar a distribuição de dose em profundidade. Por fim, para efeito de comparação, a distribuição da DgNp também foi estimada utilizando dosímetros termoluminescentes (TLDs). A metodologia desenvolvida para medição de espectros mostrou-se eficaz para posicionamento e alinhamento adequados do detector no feixe e consequentemente a medição dos espectros diretos. Os espectros incidentes experimentais mostraram boa concordância com espectros simulados. Os resultados mostraram uma distribuição bem-comportada desses coeficientes (DgNp), com tendência linear ou exponencial, com relação aos parâmetros analisados. Para um dado espectro, os valores de DgNp apresentaram decrescimento exponencial com a espessura do material simulador ao tecido mamário e dependencia linear com a glandularidade. Além disso, esses coeficientes crescem linearmente com o aumento da camada semirredutora e, consequentemente, com a energia efetiva. A partir das distribuições de DgNp (obtidas pelo Método III) foi possível estimar a dose no volume completo da mama com diferença máxima de 5,2% dos valores obtidos com o Método II. A variação da DgNp com a profundidade obtidas com TLDs mostrou-se bastante coerente com os resultados observados com a utilização do Método III. Conclui-se que é possível avaliar a dose glandular em mamografia utilizando espectros de raios X e que a metodologia proposta tem potencial para ser aplicada como procedimentos alternativos para dosimetria em mamografia. The mean glandular dose is the quantity used for dosimetry in mammography. This quantity has a strong dependence with some properties of the evaluated breast, such as its glandularity and compressed thickness. It also depends on the X-ray spectrum used for the mammographic image production, such as the target/filter combination and the tube voltage, which are related to the half value layer (HVL) of the beam. The X-ray beam characterization by means of the direct measurement of its spectrum is a complex procedure, and it is difficult to be implemented in clinical systems due to the architecture of the mammography equipment and the high photon fluence rates. These spectra provide a complete qualitative and quantitative information of the X-ray beam. The general objective of this work is to estimate mean glandular dose distributions in different depths of breast tissue-equivalent materials (bTEM) considering the X-ray spectra measured in clinical mammography devices. Radiographic techniques commonly applied for breast cancer screening were used. The behavior of the mean glandular dose normalized to the incident air kerma (DgNp), with parameters related to the breast (glandularity and compressed thickness) and to the mammographic spectra (HVL, tube voltage, target/filter combination), was evaluated. First, an experimental methodology was developed to measure X-ray spectra in clinical mammography devices. Then, the following methods for calculating the DgNp using these spectra were considered: Method I, which calculates the DgNp using the incident spectra; Method II, which uses incident and transmitted spectra by the bTEMs, and Method III, which uses incident and transmitted spectra to estimate the dose distributions in depth of the breast equivalent materials. Finally, thermoluminescent dosimeters (TLDs) were used as a comparative method to evaluate DgNp distributions. The methodology developed for measuring spectra proved to be efficient for the proper positioning and alignment of the detector and, consequently, for the measurement of direct X-ray spectra. The experimental incident spectra showed good agreement with spectra simulated in similar conditions. The results showed well-defined trends (either linear or exponential) of the distributions of these coefficients (DgNp) regarding the analyzed parameters. The DgNp values presented an exponential decay with the bTEM thickness and linear decrease with the glandularity. In addition, these coefficients increase linearly with the increase of the HVL and, consequently, with the increase of the effective energy. From the distributions of DgNp (obtained by Method III) it was possible to estimate the DgNp in the whole breast with a maximum difference of 5.2% from the values obtained using the Method II. The variation of the DgNp with the depth, obtained with TLDs, showed to be consistent with the results observed using the Method III. In conclusion, it is possible to evaluate the glandular dose in mammography examinations using X-ray spectra and the suggested methodology, with some adaptations, can be applied as an alternative procedure for dosimetry in mammography.

Esse trabalho foi desenvolvido com a finalidade de melhorar a qualidade dos serviços de calibração e testes de monitores de radiação gama, prestados pelo Laboratório de Calibração de Instrumentos do IPEN, assim como diminuir a dose ocupacional dos técnicos envolvidos no processo de calibração, seguindo os princípios de proteção radiológica. Foi realizado o desenvolvimento e a implantação de um sistema automatizado para o processo de calibração de monitores de radiação gama, constituido por (i) um dispositivo pneumático de troca dos atenuadores e (ii) uma mesa de posicionamento, ambos acionados remotamente por intermédio de um painel de comando. Também fez parte a implantação de um Sistema Irradiador Caesa-Gammatron, que aumentou o intervalo de taxa de kerma no ar, devido sua alta atividade em relação ao sistema atualmente em uso no laboratório de calibração com radiação gama. Para isso, foi necessária a instalação de um dispositivo atenuador controlado remotamente nesse sistema irradiador. Por último foi realizado uma avaliação da redução da dose ocupacional. This work was developed with the aim of improving the quality of the services of calibration and tests of gamma radiation monitors - provided by the IPEN Laboratory of Instrument Calibration - as well as reducing the occupational dose in technicians involved in the process of calibration, following the principles of radiation protection. In this study it was carried out the development and implementation of a system for adequation of the process of gamma radiation monitors calibration. It is constituted by (i) a pneumatic dispositive to exchange the attenuators and (ii) a positioning table, both actuated through a control panel. System was also implemented. A Caesa-Gammatron Irradiator, which increased the range of the air kerma rates, due to its activity higher than the current system of gamma radiation in use in the calibration laboratory. Hence, it was necessary the installation of remotely controlled in the attenuator dispositive in this irradiator system. Lastly, it was carried out an evaluation in the reduction of the occupational doses.

A dosimetria de pacientes associada à avaliação das condições de funcionamento dos equipamentos médicos e aos procedimentos empregados na realização dos exames, desempenha um papel fundamental no sistema de proteção radiológica das exposições médicas. Nesse sentido, foi realizado um levantamento em grande escala das doses recebidas pelos pacientes submetidos a exames radiológicos convencionais realizados em uma amostra representativa de estabelecimentos de saúde do estado de São Paulo. Nesse levantamento foi empregado um kit dosimétrico postal originalmente desenvolvido, que permitiu a determinação da dose de entrada na pele (DEP) através da técnica de dosimetria termoluminescente. Paralelamente foram realizadas visitas in-loco a uma sub-amostra de estabelecimentos, onde as condições de funcionamento dos equipamentos de raios X médicos e do sistema de imagem foram avaliadas empregando-se procedimentos e equipamentos já estabelecidos em protocolos de controle de qualidade. O estudo completou-se com a elaboração de um catálogo de espectros na faixa de energia do radiodiagnóstico, que, através de procedimento desenvolvido, permitiu inferir espectros equivalentes em equipamentos médicos. Na determinação dos espectros foi empregado um detector semicondutor de telureto de cádmio e zinco (CdZnTe), cujas curvas de eficiência e escape foram determinadas experimentalmente para realização do processo de correção dos espectros (stripping procedure). O processo de amostragem de estabelecimentos de saúde realizado neste estudo permitiu verificar a distribuição de equipamentos de diagnóstico por imagem e a freqüência de exames radiológicos no estado de São Paulo. A partir desses resultados foram escolhidos os exames de tórax, crânio (e seios da face) e coluna para avaliação de DEP, uma vez que os mesmos apresentam as maiores freqüências anuais de exames por 1.000 habitantes: 100, 46 e 29, respectivamente. Na técnica de amostragem dos estabelecimentos de saúde incluídos neste estudo foi empregado como critério de estratificação a quantidade anual de exames radiológicos associados ao município de localização do estabelecimento. Do total de 200 estabelecimentos sorteados, 50 participaram da primeira etapa e 38 da segunda. Um total de 83 salas de exames (ou equipamentos) e 868 pacientes foram incluídos, e um conjunto de 1415 valores de DEP foi determinado. O resultado da distribuição dos valores de DEP permitiu determinar os chamados níveis de referência, que, no caso de pacientes adultos, se mostraram bastante semelhantes aos encontrados em outros estudos internacionais. No caso de pacientes infantis, a situação é bem diferente, obtendo-se valores pelo menos 2 vezes superiores a outros recomendados internacionalmente para a radiografia infantil mais freqüente (tórax). Esse fato sugere que as práticas empregadas na realização dos exames devem ser revisadas e que recomendações específicas a esse grupo de pacientes, a partir de estudos dirigidos, sejam publicadas. Constatou-se também alguns casos de DEP elevada pelo uso desnecessário de radioscopia de localização. Os testes de desempenho dos equipamentos e a avaliação das imagens realizadas sugerem que há possibilidade de melhoria das condições de realização dos exames, sem perda de informação diagnóstica presente na imagem e com redução das doses. Alguns espectros de raios X determinados experimentalmente apresentaram divergência em relação a outros catálogos já estabelecidos, numa faixa específica de energia do espectro (entre 25 e 40 keV). Para a sua utilização em situações práticas há necessidade de algumas correções na curva de eficiência, o que não inviabiliza a metodologia e os procedimentos estabelecidos. De forma geral, os resultados encontrados neste estudo permitem traçar um panorama das exposições médicas em radiologia convencional no estado de São Paulo, contribuindo para o aperfeiçoamento de futuras pesquisas que sejam realizadas na área, ou mesmo, para a implementação de políticas públicas. Patients dosimetry, associated with the assessment of the performance of the radiological equipment and of the series of procedures employed in the accomplishment of the examinations, plays fundamental role in the radiation protection system of medical exposures. Therefore, a large-scale survey of absorbed doses was carried out in health services localized in the state of São Paulo, including patients submitted to conventional radiological examinations. In this survey a postal dosimetric kit, originally developed, was employed. It allows the evaluation of the entrance surface dose (ESD) to patients with thermoluminescence dosimeters. Also a series visits to a sub-sample of services was carried out, giving rise to the in-loco evaluation of the performance of the medical x-ray equipment and of the image system, using procedures and equipments already established in protocols of quality control. The study is completed with the elaboration of a catalogue of x-ray spectra, which provides means to infer the spectra generated by medical x-ray equipments. Measurements of x-ray spectra were carried out with a cadmium zinc telluride detector (CdZnTe), and the stripping procedure was performed taking into account both the contributions of efficiency and x-ray escape fraction, experimentally determined in this work. The stratified sampling technique furnished important data on the distribution of equipments and the annual frequency of examinations performed in the state of São Paulo. From these results radiological examinations of the chest, skull and sinus, and spine were selected for the evaluation of ESD, as their annual frequencies are the highest observed: 100, 46 and 29 per thousand inhabitants, respectively. The number of x-ray examinations carried out annually in the cities of the state was employed as the stratification criterion to construct the sample. From a total of 200 health services sampled, 50 agreed to participate of the first stage, and 38 of the second. A total of 83 rooms (or x-ray equipments) and 868 patients was included, and a set of 1415 values of ESD was measured. Diagnostic reference levels were determined with the outcomes of the distribution of ESD. For adult patients, the reference levels achieved are very similar to others obtained in international surveys. However, as far as pediatric patients are concerned, the situation is very different: the values found in this survey are twice larger than the international recommendations to chest radiography of children. This points out that the practices need to be revised and that specific recommendations to this patient group, following specific surveys, should be provided. Also, a series of high ESD values due to unnecessary localizing radioscopy were detected among our data. The results of the equipment performance tests and of the evaluation of image quality suggest that it is possible to improve the conditions of the examinations and to reduce doses to patients, without impairment of the diagnostic information. Some of the experimentally determined x-ray spectra show a discrepancy, when compared to other catalogue spectra, in a particular energy range 25 to 40 keV. The practical application of them will require some corrections in the efficiency curve, but the established methodology and procedures remain legitimate. In an extensive approach, the results of this study supply a panorama of medical exposures in conventional radiology in the state of São Paulo, contributing with resources to future research in the field and also to governmental actions.