Application of the HTR-method in the field of radiobiology: correlation of the HTR with the genotoxic parameters and measurement of the equivalent dose in aircrafts

For determination of the absorbed dose and the average LET of mixed radiation fields in space the high temperature ratio (HTR-) method was developed at the Atominstitute of the Austrian Universities based on the thermoluminescence dosimeters LiF:Mg,Ti. Due to the good results obtained with this method in space the applicability of the HTR-method was tested. The HTR-method was applied for determination of the biological relevant dose in aircrafts. Measurements were performed during several flights on the flight routes Cologne-Washington, Vienna-Miami and Vienna-Sydney. For the reason of comparison a neutron detector was used in addition. Due to the small size of the dosimeters the determination of the dependence of the average LET and the equivalent dose on the absorber thickness was performed by exposing the dosimeters in Bonner spheres of different diameter. The results show an increase of the equivalent dose up to an absorber thickness of 60 mm. This fact should be considered for a conservative evaluation of the effective dose. Furthermore the HTR-method was applied in the field of radiobiology. Dosimeters were exposed in a 62 MeV proton beam used for proton therapy in order to determine the dose- and LET-dependence on the proton range of the modulated proton beam. While the absorbed dose was constant over the range of modulation, the LET increased sharply at the end of the range. This results were consistent with biological investigations. Due to this agreement a detailed correlation of the HTR and gentoxic parameters was performed Irradiations of dosimeters and human fibroblasts were performed with Co-60 as well as of dosimeters and lymphocytes with 62 MeV protons. For both investigations a correlation of the gentoxic parameter micronuclei and the HTR could be determined. (author)