Journal article
The microdosimetric one-hit detector model for calculating the relative efficiency of the alanine pellet dosimeter in low energy x-ray beams
The alanine pellet dosimeter is a widely used reference dosimeter in both medical and industrial dosimetry across a wide range of beam qualities. A challenge when using alanine in low energy x-ray beams is its strong energy dependence; a significant decline is observed in the alanine response per dose-to-water relative to irradiations in a cobalt-60 reference field.
This decrease is caused by the physical difference in alanine to water dose ratios combined with a radiochemical decrease in the intrinsic detector efficiency but is difficult to characterize mainly due to experimental uncertainties. Here we have applied a microdosimetric one-hit detector model to characterize the intrinsic detector efficiency of the alanine pellet dosimeter in low energy x-ray beams.
Microdosimetric distributions were estimated from track structure calculations using the Geant4-DNA Monte Carlo software, where literature data was used to determine free model parameters. The model was applied to two sets of x-ray spectra with low (40 kV to 170 kV) and medium (100 kV to 300 kV) tube potential, covering a wide range of beam qualities.
A relative detector efficiency of 0.937 was obtained for the low energy set with variations between -1.0% and 1.5%, whereas the efficiency varied between approximately 0.925 and 0.985 for the medium energy set, with a strong correlation to the half-value layer of the beam. It is concluded, that the tube potential and half-value layer of an x-ray beam is not sufficient characterization to uniquely determine the relative efficiency of an alanine pellet dosimeter.
However, the variation in relative efficiency with respect to the half-value layer is small.
Language: | English |
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Year: | 2022 |
Pages: | 106659 |
ISSN: | 18790925 and 13504487 |
Types: | Journal article |
DOI: | 10.1016/j.radmeas.2021.106659 |
ORCIDs: | Hjørringgaard, Jakob G. , Ankjærgaard, Christina and Andersen, Claus E. |