title: An experimental and Monte Carlo investigation of the energy dependence of alanine/EPR dosimetry: I. Clinical x-ray beams.
abstract: The energy dependence of alanine/EPR dosimetry, in terms of absorbed dose-to-water for clinical 6, 10, 25 MV x-rays and 60Co gamma-rays was investigated by measurements and Monte Carlo (MC) calculations. The dose rates were traceable to the NRC primary standard for absorbed dose, a sealed water calorimetry. The electron paramagnetic resonance (EPR) spectra of irradiated pellets were measured using a Bruker EMX 081 EPR spectrometer. The DOSRZnrc Monte Carlo code of the EGSnrc system was used to simulate the experimental conditions with BEAM code calculated input spectra of x-rays and gamma-rays. Within the experimental uncertainty of 0.5%, the alanine EPR response to absorbed dose-to-water for x-rays was not dependent on beam quality from 6 MV to 25 MV, but on average, it was about 0.6% lower than its response to 60Co gamma-rays. Combining experimental data with Monte Carlo calculations, it is found that the alanine/EPR response per unit absorbed dose-to-alanine is the same for clinical x-rays and 60Co gamma-rays within the uncertainty of 0.6%. Monte Carlo simulations showed that neither the presence of PMMA holder nor varying the dosimeter thickness between 1 mm and 5 mm has significant effect of the energy dependence of alanine/EPR dosimetry within the calculation uncertainty of 0.3%.
authors.affiliation: National Research Council of Canada, Ottawa, K1A 0R6, Canada. zeng@irs.phy.nrc.ca
authors.forename: G G
authors.initials: GG
authors.lastname: Zeng
authors.forename: M R
authors.initials: MR
authors.lastname: McEwen
authors.forename: D W
authors.initials: DW
authors.lastname: Rogers
authors.forename: N V
authors.initials: NV
authors.lastname: Klassen
mesh_terms: D000409:Alanine / Q000737:chemistry*; D002138:Calibration; D002151:Calorimetry; D003037:Cobalt Radioisotopes / Q000627:therapeutic use; D004307:Dose-Response Relationship, Radiation; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005720:Gamma Rays; D009010:Monte Carlo Method; D017785:Photons; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D014965:X-Rays
chemical_list: D003037:Cobalt Radioisotopes; D000409:Alanine