EPR dosimetric properties of formates Tor Arne Vestad1, Eirik Malinen1, Anders Lund2, Eli Olaug Hole

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EPR Dosimetric Properties of Formates Tor Arne
Vestad1, Eirik Malinen1, Anders Lund2, Eli Olaug
Hole1 and Einar Sagstuen1 1Department of Physics,
University of Oslo, P.O. Box 1048 Blindern,
N-0316 Oslo, Norway 2Chemical Physics Laboratory,
IFM, Linköping University, S-581 83 Linköping,
Sweden
As a part of a program to develop an EPR
dosimeter suitable for clinical use (doses in the
cGy range), polycrystalline samples of lithium
formate monohydrate (HCO2LiH2O), (LiFo),
magnesium formate dihydrate (C2H2O4Mg2H2O), and
calcium formate (C2H2O4Ca) have been examined.
L-alanine was included for comparison and
reference. Samples were irradiated using 60Co
?-rays and 60 - 220 kV X-rays. The dosimeter
response was assessed using the peak-to-peak
intensity of the first-derivative EPR spectrum.
In all experiments, the microwave power and
modulation amplitudes used yielded 52 of maximum
achievable signal for each compound.
The photon energy dependencies of the EPR spectra
as a function of half value layer (HVL) in
aluminum. The HVL designation indicates photon
energies of 60kV, 100 kV, 220 kV and 60Co
?-rays.
Dose-response curves for 60Co ?-irradiated
samples were established
Lithium formate mono-hydrate is by far the best
candidate of the tested formates. It is suitable
for measuring doses down to about 0.1 Gy. LiFo is
more sensitive than alanine by a factor 5.6-6.8
in the tested photon energy range. It exhibits no
zero-dose signal and shows a linear dose response
in the measured dose range 0.2 to 1000 Gy.
The stability of the irradiation products upon
storage (fading characteristics) were
investigated. The EPR signal from LiFo is
unchanged in shape and intensity after one week
following irradiation to a dose of 10 Gy.