Evaluation of the efficiency curve of a Cadmiun Telluride detector for low-energy photon spectrometry.

The performance of a Cadmiun Telluride (CdTe) detector for low energy photon spectrometry was evaluated. Collected data were analyzed using the basic software package available with the CdTe detector system and the COLEGRAM code developed for photopeak deconvolution at LNHB/France. Several calibrated point sources were used to determine the energy versus efficiency curve. The efficiency curve was used in the determination of main X-ray intensities of (153)Sm and (177)Lu.

Primary activity standardization of 99Tc by three different absolute methods.

The activity concentration of a solution of (99)Tc was absolutely determined by liquid scintillation measurements based on the triple-to double-coincidence ratio method (TDCR) and compared with the results given by 4πß(LS)-γ(NaI) live-timed anticoincidence (with extending dead-time) and classical 4πß(PC)-γ(NaI) coincidence counting systems based on using (60)Co as the efficiency-tracing radionuclide. The results of anticoincidence and coincidence counting are, respectively, 0.18% and 0.66% higher than the result from TDCR measurements, but they are consistent within uncertainties.

Fatores de correção volumétrica na medição de atividade de 99mTc e 123I em calibradores de radionuclídeos / Volume corrections factors in the measurement of 99mTc and 123I activities in radionuclide calibrators

OBJETIVO: Determinar os fatores de correção para a variação volumétrica dos radiofármacos contidos em recipientes de diferentes geometrias. Comparar a influência desses fatores na determinação da atividade de 99mTc e 123I utilizando dois tipos de calibradores: um com câmara de ionização e outro com detector Geiger-Müller (G-M). Avaliar o desempenho de calibradores de alguns serviços de medicina nuclear em medição de atividade de 99mTc e 123I. MATERIAIS E MÉTODOS: Foram utilizados oito calibradores, frascos de vidro 10R, seringas de plástico de 3 e 5 mL e soluções de 99mTc e 123I. Os fatores de correção foram determinados a partir das medições práticas da variação da leitura do calibrador com a variação do volume da solução no recipiente. O desempenho foi avaliado em relação ao critério de aceitação de ±10% de exatidão exigida pela norma brasileira. RESULTADOS: A variação da resposta do calibrador com a variação do volume do frasco foi bem maior no calibrador que utiliza G-M. Ela também foi maior para 123I do que para 99mTc. CONCLUSÃO: Os resultados confirmam que a resposta dos calibradores depende do volume contido nos recipientes. Essa dependência é mais crítica para os calibradores equipados com detector G-M e para 123I quando comparado com 99mTc.

OBJECTIVE: To determine correction factors for the variation in volume of radiopharmaceuticals in containers of different geometries, comparing the influence of such factors on the determination of 99mTc and 123I activity with two types of calibrators - one with ionization chamber and another with Geiger-Müller (G-M) detector -; and to evaluate calibrators performance in the measurement of 99mTc and 123I activities. MATERIALS AND METHODS: Eight calibrators, 10R glass vials, 3 and 5 mL plastic syringes and 99mTc and 123I solutions were utilized. The correction factors were determined with basis on practical measurements of the variation in the calibrators' response according to the volume of radionuclide solution in the glass vials. The performance was evaluated according to the acceptance criterion of ±10% accuracy required by the Brazilian standard. RESULTS: The variation of the calibrators' response according to the variation in radionuclide volume was reasonably greater in the calibrator with G-M detector. It was also greater for 123I than for 99mTc. CONCLUSION: The results confirm that the calibrators' response depends on the radionuclide volume contained in the vials. Such dependence is more critical for the calibrators equipped with G-M detector and for 123I as compared with 99mTc.

Analytical results and effective dose estimation of the operational Environmental Monitoring Program for the radioactive waste repository in Abadia de Goiás from 1998 to 2008.

This paper presents the results of the Environmental Monitoring Program for the Radioactive waste repository of Abadia de Goiás, which was originated from the accident of Goiania, conducted by the Regional Center of Nuclear Sciences (CRCN-CO) of the National Commission on Nuclear Energy (CNEN), from 1998 to 2008. The results are related to the determination of (137)Cs activity per unit of mass or volume of samples from surface water, ground water, depth sediments of the river, soil and vegetation, and also the air-kerma rate estimation for gamma exposure in the monitored site. In the phase of operational Environmental Monitoring Program, the values of the geometric mean and standard deviation obtained for (137)Cs activity per unit of mass or volume in the analyzed samples were (0.08 ± 1.16) Bq.L(-1) for surface and underground water, (0.22 ± 2.79) Bq.kg(-1) for soil, and (0.19 ± 2.72) Bq.kg(-1) for sediment, and (0.19 ± 2.30) Bq.kg(-1) for vegetation. These results were similar to the values of the pre-operational Environmental Monitoring Program. With these data, estimations for effective dose were evaluated for public individuals in the neighborhood of the waste repository, considering the main possible way of exposure of this population group. The annual effective dose obtained from the analysis of these results were lower than 0.3 mSv.y(-1), which is the limit established by CNEN for environmental impact in the public individuals indicating that the facility is operating safely, without any radiological impact to the surrounding environment.

Teste de proficiência para medições de radioatividade na medicina nuclear / Proficiency test for radioactivity measurements in nuclear medicine

OBJETIVO: Avaliar o desempenho dos calibradores de radionuclídeos de 55 serviços de medicina nuclear brasileiros em medição de atividade de radiofármaco contendo 99Tc m. Testes de proficiência foram aplicados em 63 resultados originados do programa de comparação promovido pelo Laboratório Nacional de Metrologia das Radiações Ionizantes do Instituto de Radioproteção e Dosimetria. MATERIAIS E MÉTODOS: O desempenho foi avaliado em relação ao critério de aceitação de ±10 por cento de exatidão exigido pela norma brasileira e também aos critérios estabelecidos pela ISO/IEC Guide 43-1, e classificado como "aceitável" ou "não aceitável". Amostras de 99Tc m usadas nas comparações foram fornecidas por alguns dos participantes e calibradas no Laboratório Nacional de Metrologia das Radiações Ionizantes para determinar o valor de referência da atividade. RESULTADOS: Esta comparação com o 99Tc m mostrou que o desempenho aceitável atendendo à exigência da norma regulatória foi de 82,5 por cento, enquanto pelos critérios estabelecidos pela norma ISO/IEC 43-1 foi de 81,0 por cento. Por outro lado, calibradores de radionuclídeos com detector Geiger-Müller apresentaram desempenho inferior quando comparados com os dotados com câmara de ionização. CONCLU-SÃO: Nesta comparação, a avaliação do desempenho baseada nos critérios da ISO/IEC 43-1, os quais são aplicados a laboratórios analíticos, apesar de serem mais restritivas, foi bastante consistente com o critério de exatidão exigido pela norma nacional.

OBJECTIVE: To assess the performance of radionuclide calibrators in 55 Brazilian nuclear medicine services in the measurement of 99Tc m radiopharmaceutical activity. Proficiency tests were applied to data sets with 63 results originated from the comparison program developed by Laboratório Nacional de Metrologia das Radiações Ionizantes of Instituto de Radioproteção e Dosimetria. MATERIALS AND METHODS: The calibrators' performance was evaluated in compliance with the acceptance criterion of ±10 percent accuracy required by the Brazilian standards and also the criteria established by the ISO/IEC Guide 43-1, and classified as either "acceptable" or "non-acceptable". The samples of 99Tc m utilized in the comparison were supplied by some of the participants and calibrated at Laboratório Nacional de Metrologia das Radiações Ionizantes for determining the activity reference value. RESULTS: The present study utilizing 99Tc m has shown that 82.5 percent of the calibrators were considered as acceptable according to the Brazilian standards, while by the criteria established by ISO/IEC 43-1, 81.0 percent were considered as acceptable. On the other hand, radionuclide calibrators with Geiger-Müller detectors presented unsatisfactory performance when compared with calibrators with ionization chambers. CONCLUSION: The performance evaluation based on the ISO/IEC 43-1 criteria, which are applied to analytical laboratories, in spite of being more restrictive, has demonstrated to be quite consistent with the accuracy criterion established by the Brazilian standard.

Determination of total content and isotopic compositions of plutonium and uranium in environmental samples for safeguards purposes by ICP-QMS.

The aim of this work was to determine the concentrations and isotopic compositions of plutonium and uranium in environmental samples for safeguards purposes. An analytical method was developed with a plutonium and uranium separation procedure based on extraction chromatography (using 2mL TEVA and UTEVA columns) and detection with a quadrupole ICP-MS applying an ultra-sonic nebulizer coupled with a membrane desolvation system. Starting from blank swipes, the background equivalent concentration (BEC) was 8fg for (239)Pu and 1ng (238)U. The method was successfully applied to certified reference materials as well as to round robin samples obtained in the framework of the inter-laboratory exercise program, promoted by the Brazilian-Argentine Agency for Accounting and Control of Nuclear Materials (ABACC), together with the US Department of Energy (USDOE). After the introduction of an additional ion-exchange separation step, the methodology was applied to the IAEA-384 sediment reference sample with precise and accurate total plutonium and uranium, (240)Pu/(239)Pu, (241)Pu/(239)Pu, (234)U/(238)U and (235)U/(238)U atomic ratio results.

Proficiency tests in the determination of activity of radionuclides in radiopharmaceutical products measured by nuclear medicine services in 8 years of comparison programmes in Brazil.

Proficiency tests were applied to assess the performance of 74 nuclear medicine services in activity measurements of (131)I, (123)I, (99)Tc(m), (67)Ga and (201)Tl. These tests produced 913 data sets from comparison programmes promoted by the National Laboratory for Ionizing Radiation Metrology (LNMRI) from 1999 to 2006. The data were evaluated against acceptance criteria for accuracy and precision and assigned as Acceptable or Not acceptable accordingly. In addition, three other statistical parameters were used as complementary information for performance evaluation which related to normative requirements and to radionuclide calibrators. The results have shown a necessity to improve quality control procedures and unsatisfactory performances of radionuclide calibrators, which incorporate Geiger-Müller detectors.

The influence of uncertainties of measurements in laboratory performance evaluation using an intercomparison program of radionuclide assays in environmental samples.

To show the influence of measurement uncertainties in performance evaluation of laboratories, data from 42 comparison runs were evaluated using two statistical criteria. The normalized standard deviation, D, used by US EPA, that mainly takes into account the accuracy, and the normalized deviation, E, that includes the individual laboratory uncertainty used for performance evaluation in the key-comparisons by BIPM. The results show that data evaluated by the different criteria give a significant deviation of laboratory performance in each radionuclide assay when we analyse a large quantity of data.

Implementation of a national metrology network of radionuclides used in nuclear medicine.

The Nuclear Medicine Services (NMS) in Brazil routinely use dose calibrators to measure the activity of solutions containing radiopharmaceuticals. These solutions are administered to patients with the intention to diagnose or treat illnesses. However, for optimal results, the activity of these radiopharmaceuticals must be determined as accurately as possible. The National Laboratory for Ionizing Radiation Metrology (LNMRI) led, since 1998, a comparison program for activity measurements of radiopharmaceuticals administered to patients in the NMS with the purpose promoting quality control. This program has been carried out successfully in Rio de Janeiro, but there is a need to implement it around the country. This can be resolved through the implementation of a network of regional laboratories at various locations throughout the national territory. Currently, such a network is active at a second site, located in Brasília, covering the needs of the Center-West Region, and at a third site, located in Porto Alegre, in the South Region. This work presents the results of comparisons for the radiopharmaceuticals nuclides 131I and 99Tcm and proves that the implementation of a radionuclide metrology network is feasible and viable.

The Brazilian National Intercomparison Program (PNI/IRD/CNEN): evaluation of 15 years of data.

The Instituto de Radioproteção e Dosimetria has been coordinating the National Intercomparison Program (PNI) for 15 years, from 1991 to 2005. The objective is to evaluate the analytical performance of the laboratories in low-level activity concentration radionuclide assays in environmental samples. This work presents an evaluation of PNI data from 42 intercomparison runs, which distributed to 22 Brazilian laboratories 2511 samples evaluating 5768 radionuclide assays involving 32 radionuclides in the period from 1991 to 2004. The laboratory performance was evaluated using the Normalized Standard Deviation used by the U.S. EPA. For comparison aims, the Normalized Deviation, used by BIPM was also applied. Laboratory performance were grouped and evaluated in three periods of 5 years each. The first period shows, an average value of good performance of 71.2%, the second shows an average of 78.6% and the last an average of 82.3%. Performance for each kind of radionuclide is also presented.

Avaliação da implementação da Portaria 453 no estado de São Paulo / Evaluation of implementation of Regulation n.453 in the state of São Paulo

Uma dose maior de radiação aumenta a probabilidade de indução de efeitos danosos ao organismo. A Portaria 453 tem como objetivo reduzir estas doses, mas um número cada vez maior de cirurgiões-dentistas questiona sua necessidade. Neste trabalho a nossa meta foi a avaliaçãode 500 laudos radiométricos executados por diferentes firmas especializadas na implementação da Portaria 453 nos consultórios odontológicos do estado de São Paulo, além de verificar a utilização correta dos raios X na Odontologia...

Análise crítica dos serviços que visam a implementação da Portaria 453 em radiologia odontológica / Critical analysis of the implementation of regulation n.453 in dental radiology

Considerando os crescentes riscos associados ao uso e aplicação dos raios X na prática odontológica e a necessidade de padronizar a regulamentação técnica de proteção radiológica, resolvemos aprofundar nossa pesquisa e análise das causas que levam um número cada vez maior de cirurgiões-dentistas a questionar a Portaria 453, do Ministerio da Saúde. A escolha das variáveis baseou-se no grau de satisfação do profissional em relação à eficácia da emissão dos laudos radiométricos e à fiscalização realizada pela Vigilância Sanitária. Entre os resultados obtidos destaca-se o ceticismo d cirurgião-dentista quanto à importância do laudo radiométrico e o desconhecimento da legislação. Além disso, citamos a desinformação quanto às vestimentas de proteção radiológica e a falta de procedimentos padronizados de inspeção dos fiscais. Os resultados nã deixam dúvidas das falhas da fiscalização no auxílio aos clínicos. Identificamos como prioridade, nesta pesquisa a necessidade de formação de recursos humanos, de suporte técnico e a qualificação do pessoal envolvido na fiscalização

National intercomparison program for radiopharmaceutical activity measurements.

Since 1998, the National Laboratory for Ionizing Radiation Metrology has lead an intercomparison program for activity measurements of radiopharmaceuticals administered to patients in the Nuclear Medicine Services (NMS) with the purpose of promoting the quality control. In this work, intercomparison results with the radionuclides 67Ga, 123I, 99mTc and 201Tl from the beginning of the program to the present will be presented establishing as a consequence, the radionuclide calibrators' traceability used by the participants. The analysis of the results showed that 68% were within the limits of +/-10% required by the Brazilian Regulatory Authority that demands this accuracy band for the radiopharmaceutical measurements in the NMS. The results also demonstrate an improvement in the measurement quality that this program has provided since its beginning.

Absolute determination of activity per mass and half-life measurements of 152Eu.

A solution of 152Eu was absolutely standardized by the 4pi beta (PPC)-gamma (HPGe) coincidence counting method as part of an intercomparison program coordinated by Bureau International des Poids et Mesures. The measured activity has been used to determine the calibration factor of the LNMRI reference ionization chamber for 152Eu. The half-life of 152Eu was also determined by means of a 4pi gamma ionization chamber to be (4963.6+/-15.3) days, and compared with others published values.

166mHo: a multi-gamma standard for the calibration of Ge spectrometers.

Efficiency calibration curves for germanium detectors are usually established by using a large number of standard gamma-ray sources of specific radionuclides, that decay with few gamma-rays, or radionuclides with complex decay schemes, such as 133Ba or 152Eu. But these multi-gamma radionuclides cannot be used alone, because the gamma-rays of high intensity are irregularly distributed across the energy spectrum. 166mHo is a more suitable single source for such calibrations, because this radionuclide decays by beta(-)emission to the excited states of 166Er with the subsequent emission of about 20 strong and well distributed gamma-rays ever the energy range 50-1000 keV. Moreover, with a relatively long half-life (1200 yr) and characteristic X-rays between 40 and 50 keV, this nuclide is a good standard for the calibration of germanium detectors. The X- and gamma-ray emission probabilities of their main lines need to be known with good accuracy in order to resolve the discrepancies found in the literature. A combination of 4pi beta-gamma coincidence and X- and gamma-ray spectrometric techniques have been used to determine 50 photon emission probabilities.