RESUMO
During 1975-1982 the International Atomic Energy Agency (IAEA) in co-operation with the World Health Organization (WHO) carried out 603 absorbed dose determinations for 60Co gamma-ray beams for 278 radiotherapy institutes in 60 countries. The participants were asked to irradiate capsules containing LiF powder to 2 Gy in 5 cm of water. The percentage of the determinations in which the deviation between the institutes quoted dose and the IAEA measured dose was within +/- 5% was 62%. In 17% of the determinations, the deviation was more than +/- 10%. For around 70% of the institutes the deviation decreased when further measurements were carried out.
Assuntos
Radioisótopos de Cobalto/uso terapêutico , Compostos de Lítio , Teleterapia por Radioisótopo/normas , Dosagem Radioterapêutica/normas , Fluoretos , Agências Internacionais , Lítio , Serviços Postais , Dosimetria TermoluminescenteRESUMO
The IAEA-WHO postal dose comparison service for cobalt-60 teletherapy dosimetry is an ongoing programme aimed at improving dosimetric accuracy in IAEA-WHO Member States. LiF dosemeters were irradiated under specified conditions in a water phantom at the participating radiotherapy centres and returned to the IAEA's Dosimetry Labotatory for evaluation. The participants filled in a data sheet giving numerical values of physical factors (such as per cent depth dose, tissue-air ratio, etc.) that they employed. Nearly 65% of the comparisons showed deviations within +/- 5%, a figure which is believed to represent the overall uncertainty of the method itself. Almost 10% of the measurements deviated more than +/- 15%. It appears that participants applying 'in phantom' output measurements have better control over the dose they administer. Many of the errors observed are due to the use of faulty values for the various physical factors employed, and to the fact that often a check of the output just before the irradiation of the LiF dosemeters was not carried out.