Comparison of EPR response of pure alanine and alanine with gadolinium dosimeters exposed to TRIGA Mainz reactor

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Abstract

The development of Neutron Capture Therapy (NCT) for cancer treatments has stimulated the research for beam characterizationin order to optimize the therapy procedures. The NCT has found to be promising for treatments of tumours which hardly can betreated with other techniques, such as gliomas. Alongside with the improvements of this technique, the development ofprocedures for the beam characterization arouses great interest in order to optimize the therapy protocol by reliably determiningthe various (neutronic and photonic) components of the mixed beam usually employed for therapy.Electron Paramagnetic Resonance (EPR) dosimetry for electron and photon beams with alanine has attracted the attention of manyresearch groups for dosimetric purposes. Furthermore, the applications of EPR dosimetry for high LET radiation beams, such ascarbon ions and neutrons, are continuously increasing. This is because of the very good dosimetric features of alanine EPRdetectors such as: tissue equivalence for photon beams, linearity of its dose-response over a wide range, high stability of radiationinduced free radicals, no destructive read-out procedure, no need of sample treatment before EPR signal measurement and lowcost of the dosimeters. Moreover, in order to improve the sensitivity to thermal neutrons of alanine dosimeters the addition ofnuclei such as gadolinium oxidewas previously studied.The choice of Gd as additive nucleus is due to its very high capture cross section to thermal neutrons and to the possibility forsecondary particles produced after interaction with thermal neutrons of releasing their energy in the neighbourhood of thereaction site. In particular, it was found that low concentration (i.e. 5% by weight) of gadolinium oxide brings about an neutronsensitivity enhancement of more than 10 times without heavily reducing tissue equivalence.We have studied the response of alanine pellets with and without gadolinium exposed to the thermal column of the TRIGA Mark IIresearch reactor at the University of Mainz. Pure alanine dosimeters used were produced by Synergy Health (Germany) whereas the Gd-added dosimeters were produced atthe University of Palermo. The irradiations were performed inside polyethylene holders to guarantee charged particles equilibriumconditions.The results of EPR experiments are compared to Monte Carlo (MC) simulations aimed at obtaining information about thecontribution of the various components to the total dose measured by means of EPR dosimeters. For alanine dosimeters a goodagreement between experimental data and MC simulation have been achieved.
Original languageEnglish
Number of pages1
Publication statusPublished - 2015

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