Résumé
Objective To develop a rapid and reliable method for determination of 210Po using large-area grid ionization chamber α spectrometry.Methods Samples were digested using a microwave digestion system.After preparation of sample source,the concentration of 210Po in clam was detected by large-area grid ionization chamber (φ 25 cm).209Po tracer was used to obtain the recovery.Results Large-area grid ionization chamber could achieve better counting and α spectrum resolution when the optimized thickness was 250 μg/cm2.By spiking 209Po tracer in clam,the minimum detectable activity was 9.870 × 10 4 Bq and the recovery of 210Po was 98％.Conclusions Compared with the traditional method,the developed method can avoid separation process,using less quantity of sample (0.2-0.5 g dry) and simplify the measurement process.This method may be has broad application prospects.
Résumé
Objective To verify the reliability of dose parameters of radiotherapy under reference and non-reference conditions by using TLD.Methods Dose parameters were verified by using TLDs under reference and non-reference conditions,including the maximum dose in axel of 5 electron beams with energy of 9 MeV and the variations of dose by depth,source-skin distance,exposure field and 45° wedge for 10 photon beams with energy of 6 MV in 5 hospitals.Results The average relative deviation of 6 MV photon beam measured between TLDs and finger ionization chambers were 4.45％,within ± 7％ as required by IAEA.The average relative deviation of 9 MeV electron beam measured between TLDs and plane parallel chambers were 2.45％,within ± 5％ was required by IAEA.Conclusions Measuring dosimetric parameters by using TLDs under reference and non-reference conditions was reliable and feasible.
Résumé
En el trabajo se examinan la concepción y el diseño original de las instalaciones del Centro de Isótopos y las modificaciones a que fueron sometidas durante 15 años de operación a los efectos de cumplir las regulaciones de Buenas Prácticas de Fabricación no existentes en el momento de su puesta en operación. Se presta particular énfasis a los cambios realizados a celdas calientes y cajas de guantes, también a algunos aspectos de los procesos tecnológicos. El trabajo realizado permitió que las producciones del Centro de Isótopos cumplan estándares internacionales y que sus instalaciones se hayan podido validar en correspondencia con las regulaciones nacionales. Se indican pasos encaminados no solo a cumplir los requisitos exigidos por las normas ISO 9000 y las BPF, sino a asegurar la optimización y flexibilización en la utilización de las instalaciones.
The paper discusses the conception and original design of the Isotope Centres facilities, and structural changes made to the centre over 15 years of operation with the aim of meeting the Good Manufacturing Practices Regulations nonexistent at the time of its commissioning. Particular emphasis is given to the changes made to hot cells, glove boxes, and also some aspects related to technological processes. As a result, the CENTIS productions fulfil international standards and its facilities have been validated in correspondence with the national regulations. Steps are directed not only to meet the requirements of ISO 9000 and GMP, but to ensure optimization and flexibility in the use of the facilities.
Résumé
Objective To investigate the features of 2-D air vented ionization chamber array MatriXX system to use the QA procedures of radiotherapy. Methods Some important QA procedure of clinical radiotherapy practice were investigated by using a MatriXX system and a phantom made in house, mainly including the calibration of MatriXX, the off-axis rate (OAR) of virtual wedge fields, the connection between two half-fields or two asymmetry-fields, the skillful adjustment of the clinac flat filter, the 2-D dose distribution verification of radiotherapy planning, the influence of scatter screen to a large area electron beam field, the effect and best thickness and shielding position of block for a large area electron beam fields with scatter screen. Results The OAR of any virtual wedge field can be measured by a MatriXX system in a single irradiation. The conjunction accuracy of two half-fields or two asymmetry-fields may be less than 1 ram. The difference between the calculated and measured dose of any point or any isodose or any OAR of a field can be determined by using a MatriXX system. After the adjustment of the elinae flat filter with the help of MatriXX system, the flatness and symmetry of the field are 1. 85 % and 0.98 %, respectively. The dose characteristic of a large area electron beam field may be distinctively influenced by a scatter screen, and under this condition, the block faraway from the shielded target can hardly protect the organ at risk, and directe block which is put on or near the organ at risk is perfect. Conclusion Compared with conventional ionization chamber (Farmer type) or film dose measuring, the MatriXX combined with the OmniPre I'mRT software is much more convenient and effective in QA practice of clinical radiotherapy, and it's a perfect tool for the QA procedure of radiation therapy.
Résumé
Se presentan los resultados de la comparación nacional de la medición de actividad de 131I con activímetros, organizada en Cuba en el 2007. Estos resultados contribuyen a establecer la incertidumbre y la trazabilidad de los valores de actividad de 131I, determinados en los activímetros de las diferentes instituciones participantes: 9 hospitales y dos laboratorios del Centro de Isótopos que participaron directamente en la producción de los radiofármacos. Si consideramos solamente la proporción de resultados satisfactorios, el desempeño evidenciado por los participantes es igual al alcanzado en las comparaciones de este tipo, organizadas del 2002 al 2004 en el país. No obstante, la estimación razonable de la incertidumbre de la actividad de 131I medida en el activímetro, realizada por la mayoría de los participantes en el 2007, muestra un resultado cualitativamente superior con respecto al obtenido en el 2002-2004. Se reportaron los resultados del ejercicio bilateral de medición de 131I entre el Departamento de Metrología de Radionúclidos del Centro de Isótopos y el Laboratorio Nacional de Metrología de las Radiaciones Ionizantes del Instituto de Protección Radiológica y Dosimetría de Brasil. Concebido como complemento de la comparación nacional, este ejercicio bilateral proporciona evidencias adicionales de la comparabilidad de los patrones de medición utilizados para calibrar las disoluciones y muestras de referencia de 131I en el Departamento de Metrología de Radionúclidos del Centro de Isótopos.
Results from the national comparison of 131I activity measurements with radionuclide calibrators in Nuclear Medicine, organized in Cuba in 2007, are shown. These results contribute to establish the uncertainty and traceability of the 131I activity values measured with radionuclide calibrators of the participating institutions: 9 hospitals and two laboratories of the Isotope Centre directly involved in radiopharmaceuticals’ production. Concerning the proportion of acceptable results, no improvement was observed in the participants’ performance compared to results shown in such kind of exercises organized in the country during 2002-2004. On the other hand, the reasonable uncertainty estimate of the 131I measurements reported by most of the participants show a qualitatively superior outcome in 2007 compared to the result obtained in the previously organized exercises. Moreover, the outcome of the bilateral comparison for 131I activity measurements between the Radionuclide Metrology Department of the Isotope Centre (CENTIS-DMR) and the National Metrology Laboratory for Ionizing Radiation of the Brazilian Institute of Radiation Protection and Dosimetry (LNMRI-IRD) is also shown. This bilateral exercise provides additional evidences on comparability of the CENTIS-DMR measurement standards used to calibrate 131I reference solutions and samples.