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EPR dosimetric properties of formates
Tor Arne Vestad1, Eirik Malinen, Anders Lund
1Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway.
Summary
Lithium formate monohydrate shows promise as an electron paramagnetic resonance (EPR) dosimeter for clinical use. This material is highly sensitive, stable, and offers a linear dose response, outperforming L-alanine.
Area of Science:
- Materials Science
- Radiation Dosimetry
- Spectroscopy
Background:
- Development of clinical electron paramagnetic resonance (EPR) dosimeters requires materials sensitive to low radiation doses (cGy range).
- Formate salts (lithium, magnesium, calcium) were investigated as potential EPR dosimetry candidates.
- L-Alanine was used as a reference standard for comparison.
Purpose of the Study:
- To evaluate polycrystalline lithium formate monohydrate, magnesium formate dihydrate, and calcium formate as potential EPR dosimeters for clinical applications.
- To assess the dosimetric properties of these materials, including sensitivity, linearity, and stability.
- To compare the performance of lithium formate monohydrate with L-alanine.
Main Methods:
- Samples of lithium formate monohydrate, magnesium formate dihydrate, and calcium formate were irradiated with 60Co gamma-rays and 60-220 kV X-rays.
- Electron paramagnetic resonance (EPR) spectra were analyzed using the peak-to-peak amplitude of the first-derivative signal.
- Dose-response curves were constructed, and the influence of photon energy, microwave power, and modulation amplitude was studied. Signal stability upon storage was also assessed.
Main Results:
- Lithium formate monohydrate demonstrated superior performance, suitable for measuring doses down to approximately 0.1 Gy.
- It exhibited a sensitivity 5.6-6.8 times higher than L-alanine, a linear dose response from 0.2 to 1000 Gy, and no zero-dose signal.
- The EPR signal of lithium formate monohydrate remained stable for at least one week after irradiation. Other formates were less suitable, though calcium formate showed some interesting properties.
Conclusions:
- Lithium formate monohydrate is a highly promising candidate for clinical EPR dosimetry due to its excellent sensitivity, linearity, and stability.
- Its performance surpasses that of L-alanine, making it suitable for measuring a wide range of clinically relevant radiation doses.
- Further investigation into calcium formate's EPR dosimetric properties may also be warranted.