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.

Response of chronic hypoxic cells to low dose-rate irradiation

“…Dosimetry was performed by use of solid-state electron paramagnetic resonance (EPR) spectroscopy. Parallel to irradiation of cells, tablets of polycrystalline lithium formate monohydrate (HCO 2 Li H 2 O) were also irradiated (Vestad et al 2003(Vestad et al , 2004. The tablets were produced using a 5.0 mm diameter Weber (Paul-Otto Weber, Remshalden, Germany, PW10, Nr W 15093-0796) pellet press (10 kN for 1 min).…”

Lithium formate EPR dosimetry for accurate measurements of absorbed dose in radiotherapy

“…Lithium formate has shown to be a robust dosimeter material with high stability of the radiation induced free radicals, a linear dose response over a wide range (0.5 -1000 Gy) and up to seven times higher sensitivity than the most common EPR dosimetry material alanine (Vestad et al, 2003;Vestad et al, 2004;Lund et al, 2002). The dosimetry system was developed during a dissertation work studying sensitive materials for EPR dosimetry (Gustafsson, 2008).…”

Campos pequenos de radiação e materiais alternativos em dosimetria com espectroscopia de ressonância magnética eletrônica

“…Gy (Malinen et al, 2007), 5 mm diameter x 2.5 mm height and doses 3 -6 Gy (Waldeland et al, 2010b), 5 mm diameter x 3.5 ± 0.2 mm height and doses 0.5 -2.5 Gy (Vestad et al, 2004a), especially applied with low doses.…”

“…Lithium formate pellets were already reported in literature, standing out because of the non-necessity of binders (Vestad et al, 2004a). A test with pellets of dimensions 9.7 mm height and 4 mm diameter was carried out.…”

“…One of the advantages is that it presents effective atomic number (zeff) close to water (Vestad et al, 2004a), and a single line spectrum, which is less complex than alanine signal, as the models in figure 18. Thus, as alanine was investigated in clinical applications (Chu et al, 1989;Gall et al, 1996;Kuntz et al, 1996;De Angelis et al, 1999;De Angelis et al, 2000;Cieszielski et al, 2003;Schultka et al, 2006;Wagner et al, 2008;Schaeken et al, 2010;Garcia et al, 2011;Wagner, Anton and Vorwerk, 2011;Tanderup et al, 2013;Rech et al, 2014;Alves et al, 2015;BravoMiranda et al, 2015) so was lithium formate (Gustafsson, Lund and Olsson, 2008;Adolfsson et al, 2010;Waldeland et al, 2010a).…”