Measurement of the absolute gamma emission intensities from the decay of Th-229 in equilibrium with progeny.

There are few long-lived radionuclides yielding high intensity gamma-rays emission with energies ranging from 100 keV to 500 keV that can be applied as radioactive gamma standard to calibrate HPGe detectors. Furthermore, this energy range represents the main emitted energies of the majority of radionuclides used in nuclear medicine. The Brazilian National Laboratory for Ionizing Radiation Metrology (LNMRI/IRD/CNEN) has attempted to identify radionuclides that have the potential to be used as a calibration source due to their long half-life as well as their emission spectrum. Hence, LNMRI promotes standardization studies of gamma-emitting radionuclides that meet these criteria on order to disseminate them. Thorium-229, with its well-defined energies and relatively high intensities, is one such candidate radionuclide for the energy and full-energy peak efficiency calibration of high-purity gamma spectrometers. Thorium-229 was standardized by the method of 4παß(LS)-γ(NaI(Tl)) live timed anticoincidence counting. The emission intensities of gamma-rays associated with the decay of 229Th have been determined by HPGe gamma ray spectrometry with accuracy and precision. The results are in agreement with current literature data.

68(Ge+Ga) activity standardization by 4πß(LS)-γ(NaI(Tl)) anticoincidence counting measurements.

In this work, a 68(Ge+Ga) solution has been standardized at the National Institute of Ionizing Radiation Metrology (LNMRI), in Brazil, in the frame of an international key comparison CCRI(II)-K2.Ge-68 piloted by National Institute of Standards and Technology (NIST/USA). The 4πß(LS)-γ(NaI(Tl)) anticoincidence method with live-time and extended dead-time was used and its result was validated by 4πß(LS)-γ(NaI(Tl)) coincidence counting and liquid scintillation counting using the Triple to Double Coincidence Ratio (TDCR) method. The deviations of the activity concentration values of coincidence and TDCR measurements from the anticoincidence result were 1.7% and 0.63%, respectively, which were within experimental evaluated uncertainties at ~95% level of confidence (coverage factor k = 2). The combined relative standard uncertainties were 0.65%, 0.70% and 0.53% for anticoincidence, coincidence and TDCR methods, respectively. These values are consistent with the results reported by Cessna at the ICRM2017 conference.

Standardization of 106Ru/Rh by live-timed anticoincidence counting and gamma emission determination.

The absolute activity standardization measurement system of radionuclide by live-timed anticoincidence counting was implemented at LNMRI in 2008 to reduce the effects of some correction factors on the determination of activity with coincidence counting technique used for decades in the laboratory, for example, the corrections of dead time and resolution. With the live-timed anticoincidence system, the variety of radionuclides that can be calibrated by LNMRI was increased in relation to the type of decay. The objective of this study was to standardize the 106Ru activity, determine gamma emission probabilities by spectrometric method for some energies, and estimate measurement uncertainties.

Absolute standardization of the impurity (121)Te associated to the production of the radiopharmaceutical (123)I.

(123)I is widely used for radiodiagnostic procedures. It is produced by reaction of (124)Xe (p,2n) (123)Cs →(123)Xe →(123)I in cyclotrons. (121)Te and (125)I appear in a photon energy spectrum as impurities. An activity of (121)Te was calibrated absolutely by sum-peak method and its photon emitting probability was estimated, whose results were consistent with published results.

Traceability from governmental producers of radiopharmaceuticals in measuring (18)F in Brazil.

Since the inception of its proficiency test program to evaluate radionuclide measurement in hospitals and clinics, the National Metrology Laboratory of Ionizing Radiation-LNMRI, that represents Brazilian National Metrology Institute (NMI) for ionizing radiation has expanded its measurement and calibration capability. Requirements from the National Health Surveillance Agency from Ministry of Health (ANVISA), to producers of radiopharmaceuticals provided an opportunity to improve the full traceability chain to the highest level. Fluorodeoxyglucose (FDG-(18)F) is the only radiopharmaceutical simultaneously produced by all Brazilian radiopharmaceutical production centers (RPCs). By running this proficiency test, LNMRI began to provide them with the required traceability. For evaluation, the ratio of RPC to reference value results and ISO/IEC17043:2010 criteria were used. The reference value established as calibration factor on the secondary standard ionization chamber was obtained from three absolute measurements systems, and routinely confirmed in each round of proficiency test by CIEMAT/NIST liquid scintillation counting. The γ-emitting impurities were checked using a High-Purity Germanium (HPGe) detector. The results show that Brazilian RPCs are in accordance with (accuracy within ±10%) the Brazilian standard for evaluation of measurements with radionuclide calibrators (CNEN NN 3.05., 2013). Nevertheless, the RPCs should improve the methodology of uncertainty estimates, essential when using the statistical criteria of ISO/IEC 17043 standard, in addition to improving accuracy to levels consistent with their position in the national traceability chain.

Radioactivity measurements of 177Lu, 111In and 123I by different absolute methods.

The activities of (177)Lu, (111)In and (123)I solutions have been absolutely determined using three different measurement methods. (177)Lu solution was standardized using the 4πß(PC)-γ(NaI) coincidence and 4πß(LS)-γ(NaI) live-timed anticoincidence methods. For the (111)In and (123)I solutions, besides these two mentioned methods, the coincidence sum-peak method was also applied. The measured activities results using these different methods are consistent within the evaluated experimental uncertainties demonstrating the equivalence of these methods. As an additional contribution to nuclear data, the half-lives have been determined using a well type IG12 ionization chamber.

Standardization of (166m)Ho and 243Am/239Np by live-timed anti-coincidence counting with extending dead time.

The National Laboratory for Metrology of Ionizing Radiation (LNMRI)/Brazil acquired (166m)Ho and (243)Am/(239)Np solutions from commercial suppliers in order to realize primary standardization and therefore reducing the associated uncertainties. The method used in the standardization was the live-timed 4πß(LS)-γ(ΝaI(Tl)) anticoincidence counting. The live-timed anticoincidence system is operated since 2006 in LNMRI and is composed of two MTR2 modules donated by Laboratoire National Henri Becquerel (LNE-LNHB)/France. The data acquisition system uses a homemade LabView program and an Excel file for calculus. These systems have been used for primary standardization at LNMRI for many radionuclides and recently took part in the (124)Sb and (177)Lu International Key Comparisons with good performance.

Primary activity standardization of (57)Co by sum-peak method.

The sum-peak method was applied to standardize a (57)Co solution within the framework of an international comparison organized by International Atomic Energy Agency, in 2008, aimed toward international traceability of activity measurements. A planar germanium detector was used with the sources placed on top of the detector for activity determination measurements. An analytical expression for accidental summing correction was derived and the effect of the germanium characteristic KX-ray escape peak of 112keV was taken into account. The standard uncertainty associated to the activity concentration value was 0.37% and the result was compared with other measurement methods.

The use of instrumental neutron activation and multivariate statistic analyses in differentiation of Brazilian phosphate ores.

Phosphated rocks from three ores located in the Middle-West region of Brazil can be used as low-level radioactive reference material due to the fact that they contain significant concentrations of thorium and, in some cases, of uranium. This paper describes the procedure to characterise those samples using several analytical methods. Statistical analysis and correlations studies have shown several geochemical similarities and the results obtained suggest the possibility to produce a reference material composed of a mixture of two similar ores.

Performance of dose calibrators in Brazilian hospitals for activity measurements.

In order to obtain information on the accuracy of activity measurements in Brazilian hospitals, several intercomparison exercises have been organized since 1998. The first exercise consisted of two intercomparison runs of 131I and 99mTc and had the participation of 21 hospitals localized in Rio de Janeiro city and surroundings. The second, with 131I (47 hospitals) and 123I (12 hospitals), had the participation of hospitals localized in the whole country. The results were analyzed under the statistical point of view and conformity to the norms of Regulatory Authority. These results have shown that such exercises are necessary to improve the quality of the measurements and to identify those instruments that are producing incorrect values.

Metrological capability of the Brazilian laboratories of analyses of radionuclides in environmental samples.

The metrological capability of 24 Brazilian laboratories of radionuclide determinations in environmental samples was analysed for purposes to establish requirements for accreditation of laboratory for each radionuclide. For each type of analysis, the range of activity per unit mass or volume, the range of the reference value and its correspondent uncertainty were described. The accuracy was established using the statistical criteria of USE.P.A. for the laboratory performance classification. The precision of the analyses, expressed by its variation coefficient of the laboratory determinations, was classified in intervals of 5%. The data base was constituted by 3013 results of analyses obtained in 28 intercomparison runs performed from 1991 to 2000, for K, Th, Unat, gross alpha, gross beta, and other 27 radionuclides, in matrices of water, soil, vegetation, air filter and milk. The quality criteria established were the variation coefficient less than 5% and good performance in intercomparison runs. Results included from 5% to 10% are also considered, for special types of matrices and radionuclides.

Absolute measurements of photon emission probabilities of 169Yb.

A solution of 169Yb was absolutely standardized by the 4pi(EC,X)-gamma coincidence counting method and the result was used to obtain direct measurements of gamma-ray emission probabilities with a coaxial HPGe detector. The empirical relation proposed by (Vaño, F., Gonzalez, L., Gaeta R., Gonzalez, J.A., 1975. An empirical function which relates the slope of the Ge efficiency curves and the active volume Nucl. Instr. Meth. 123, 573) was tested using the gamma spectral response above 200 keV. The half-life of 169Yb was also measured with a 4pi gamma ionization chamber.

Intercomparison of 131I and 99mTc activity measurements in Brazilian nuclear medicine services.

This work outlines the quality assurance program for the activity measurements of the most used radionuclides at Brazilian Nuclear Medicine Services (NMS). The program aims to guarantee that the patient is given the correct prescribed amount of activity in diagnostic or therapeutic applications. This accurate administration depends upon proper use and calibration of the activity meters by the NMS. Underestimation of administered activity in diagnostic practices could delay correct diagnosis disturbing the value of the investigation. On the other hand, the overestimation would be worse, mainly in therapeutic applications, because an unnecessarily high absorbed dose would be delivered to the patient. The preliminary results of intercomparison for 131I and 99mTc showed that many activity meters used at NMS's present problems giving results up to 41% greater than the reference values determined at the National Metrology Laboratory for Ionizing Radiation (LNMRI) which is recognized as the Brazilian authorized metrology laboratory for ionizing radiation. These results have demonstrated that the NMS should improve the accuracy of the activity measurements of the radionuclides administered to the patients and establish the traceability to the national standards of measurements. These standards are based on a pressurized well-type ionization chamber installed at LNMRI and calibrated with reference sources standardized by absolute methods. The protocol of the intercomparison and recommendations made in order to minimize errors in measuring procedures are described and results are discussed.

Radiologia diagnóstica e programa de garantia de qualidade: avaliaçäo crítica / Diagnostic Radiology and quality assurance program: critical evaluation

O Programa de Garantia de Qualidade, implementado no Serviço de Radiologia do Hospital da Polícia Militar - RJ, propiciou a reduçäo de 70 por cento na taxa de rejeiçäo de filmes e de 75 por cento nos custos. Entretanto, a descontinuidade do Programa tem conduzido ao retorno a situaçäo anterior a implementaçäo.

A Quality Assurance Program, implemented at the Radiology Service of the Hospital of the Military Police in Rio de Janeiro, brought about a reduction of 70% in the number of rejected films and 75% in the costs. The discontinuation of the program has however lead to a return to the former conditions.

Avaliando serviços de radiologia diagnóstica / Evaluate service of the diagnostic radiology

Radiação ionizante tem sido, cada vez mais, utilizada no diagnóstico e tratamento de doenças, sem a adequada adoção de métodos que garantem a qualidade do exame como um todo. Um Sistema de Garantia de Qualidade que vise reverter este cenário, depende das características de cada unidade, na qual Programas de Qualidade serão implementados. A avaliação preliminar de Serviços de Radiologia Diagnóstica, no que concerne a complexidade, oferta e qualidade dos serviços e disponibilidade de pssoal, constataram a utilização de técnicas de baixa voltagem, a não realização de testes de aceitação de aprelhos e acessórios e a não existência de profissional responsável pela proteção radiológica, entre outras limitações e deficiências.

The use of ionizing radiation is steadily increasing in diagnosis and treatment of diseases, in many cases however without the adoption of suitable methods that would garantee the quality of the exam as a whole. Improvements in this respect must be based on the present characteristics of the units in which Quality Control is to be introduced. Preliminary evaluation of Diagnostic Radiology Services showed, among other problems, the preferential use of low-voltage X-rays, the absence of acceptance triais of equipment and acessories and the lack of professionals responsible for radiological protection.