title: Electron paramagnetic resonance (EPR) dosimetry using lithium formate in radiotherapy: comparison with thermoluminescence (TL) dosimetry using lithium fluoride rods.
abstract: Solid-state radiation dosimetry by electron paramagnetic resonance (EPR) spectroscopy and thermoluminescence (TL) was utilized for the determination of absorbed doses in the range of 0.5-2.5 Gy. The dosimeter materials used were lithium formate and lithium fluoride (TLD-100 rods) for EPR dosimetry and TL dosimetry, respectively. 60Co gamma-rays and 4, 6, 10 and 15 MV x-rays were employed. The main objectives were to compare the variation in dosimeter reading of the respective dosimetry systems and to determine the photon energy dependence of the two dosimeter materials. The EPR dosimeter sensitivity was constant over the dose range in question, while the TL sensitivity increased by more than 5% from 0.5 to 2.5 Gy, thus displaying a supralinear dose response. The average relative standard deviation in the dosimeter reading per dose was 3.0% and 1.2% for the EPR and TL procedures, respectively. For EPR dosimeters, the relative standard deviation declined significantly from 4.3% to 1.1% over the dose range in question. The dose-to-water energy response for the megavoltage x-ray beams relative to 60Co gamma-rays was in the range of 0.990-0.979 and 0.984-0.962 for lithium formate and lithium fluoride, respectively. The results show that EPR dosimetry with lithium formate provides dose estimates with a precision comparable to that of TL dosimetry (using lithium fluoride) for doses above 2 Gy, and that lithium formate is slightly less dependent on megavoltage photon beam energy than lithium fluoride.
authors.affiliation: Department of Physics, University of Oslo, P.O. Box 1048, Blindern, N-0316 Oslo, Norway.
authors.forename: Tor Arne
authors.initials: TA
authors.lastname: Vestad
authors.forename: Eirik
authors.initials: E
authors.lastname: Malinen
authors.forename: Dag Rune
authors.initials: DR
authors.lastname: Olsen
authors.forename: Eli Olaug
authors.initials: EO
authors.lastname: Hole
authors.forename: Einar
authors.initials: E
authors.lastname: Sagstuen
mesh_terms: D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods; D005459:Fluorides / Q000528:radiation effects*; D005561:Formates / Q000528:radiation effects*; D018020:Lithium Compounds / Q000528:radiation effects*; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013819:Thermoluminescent Dosimetry / Q000295:instrumentation / Q000379:methods
chemical_list: D005561:Formates; D018020:Lithium Compounds; C030544:formic acid; C027651:lithium fluoride; D005459:Fluorides