Dosimetry intercomparison for partial body x-irradiation of rats.

An X-ray dosimetry intercomparison for partial body irradiations has been performed among a number of laboratories cooperating within EULEP (European Late Effects Project Group) using mailed acrylic plastic rat phantoms. The main objective of this study was to assess the adequacy of exposure arrangements and dosimetry procedures applied to rat partial body irradiations at the participating institutes. The dose and dose distribution in lung and liver substitute material have been measured with dual thermoluminescent (TL) dosemeters LiF and CaF2:Mn. The doses from scattered radiation in the shielded parts of the phantom have also been assessed. The results of the dose intercomparison show that in the first instance six out of the eight participating institutes obtain dose values which differ by more than 5% from the standard dose. Inconsistencies are observed between the lung and liver doses administered at the same institute. After consultation, four institutes indicated the cause for their deviating dose values and quoted revised results which are closer to the standard value. Large dose gradients are measured, since six out of the eight participants applied unilateral exposures. This project has indicated the need for repeated intercomparisons and for improvements in dosimetry and irradiation procedures for partial body irradiations.