The energy dependence of lithium formate and alanine EPR dosimeters for medium energy x rays.
OBJECTIVE
To perform a systematic investigation of the energy dependence of alanine and lilthium formate EPR dosimeters for medium energy x rays.


METHODS
Lithium formate and alanine EPR dosimeters were exposed to eight different x-ray beam qualities, with nominal potentials ranging from 50 to 200 kV. Following ionometry based on standards of absorbed dose to water, the dosimeters were given two different doses of approximately 3 and 6 Gy for each radiation quality, with three dosimeters for each dose. A reference series was also irradiated to three different dose levels at a 60Co unit. The dose to water energy response, that is, the dosimeter reading per absorbed dose to water relative to that for 60Co gamma-rays, was estimated for each beam quality. In addition, the energy response was calculated by Monte Carlo simulations and compared to the experimental energy response.


RESULTS
The experimental energy response estimates ranged from 0.89 to 0.94 and from 0.68 to 0.90 for lithium formate and alanine, respectively. The uncertainties in the experimental energy response estimates were typically 3%. The relative effectiveness, that is, the ratio of the experimental energy response to that following Monte Carlo simulations was, on average, 0.96 and 0.94 for lithium formate and alanine, respectively.


CONCLUSIONS
This work shows that lithium formate dosimeters are less dependent on x-ray energy than alanine. Furthermore, as the relative effectiveness for both lithium formate and alanine were systematically less than unity, the yield of radiation-induced radicals is decreased following x-irradiation compared to irradiation with 60Co y-rays.
Waldeland
Einar
E
Department of Medical Physics, The Norwegian Radium Hospital, Oslo University Hospital, N-0310 Oslo, Norway. einar.waldeland@oslo-universitetssykehus.no
Hole
Eli Olaug
EO
Sagstuen
Einar
E
Malinen
Eirik
E
D000409:Alanine; D004307:Dose-Response Relationship, Radiation; D004578:Electron Spin Resonance Spectroscopy; D004735:Energy Transfer; D005561:Formates; D016014:Linear Models; D009010:Monte Carlo Method; D011874:Radiometry / Q000379:methods*; D014867:Water
D005561:Formates; D014867:Water; C030544:formic acid; D000409:Alanine