IAEA-WHO cobalt-60 teletherapy dosimeter service using mailed LiF dosemeters. A survey of results obtained during 1970-75

Abstract

LiF dosemeters were irradiated under specified conditions in a water phantom at the participating radiotherapy centres and returned to the IAEA's Dosimetry Laboratory 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 +or-5%, a figure which is believed to represent the overall uncertainty of the method itself. Almost 10% of the measurements deviated more than +or-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.