The development of Neutron Capture Therapy (NCT) for cancer treatments has stimulated the research for beam characterization
in order to optimize the therapy procedures. The NCT has found to be promising for treatments of tumours which hardly can be
treated with other techniques, such as gliomas. Alongside with the improvements of this technique, the development of
procedures for the beam characterization arouses great interest in order to optimize the therapy protocol by reliably determining
the 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 many
research groups for dosimetric purposes. Furthermore, the applications of EPR dosimetry for high LET radiation beams, such as
carbon ions and neutrons, are continuously increasing. This is because of the very good dosimetric features of alanine EPR
detectors such as: tissue equivalence for photon beams, linearity of its dose-response over a wide range, high stability of radiation
induced free radicals, no destructive read-out procedure, no need of sample treatment before EPR signal measurement and low
cost of the dosimeters. Moreover, in order to improve the sensitivity to thermal neutrons of alanine dosimeters the addition of
nuclei 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 for
secondary particles produced after interaction with thermal neutrons of releasing their energy in the neighbourhood of the
reaction site. In particular, it was found that low concentration (i.e. 5% by weight) of gadolinium oxide brings about an neutron
sensitivity 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 II
research reactor at the University of Mainz.
Pure alanine dosimeters used were produced by Synergy Health (Germany) whereas the Gd-added dosimeters were produced at
the University of Palermo. The irradiations were performed inside polyethylene holders to guarantee charged particles equilibrium
conditions.
The results of EPR experiments are compared to Monte Carlo (MC) simulations aimed at obtaining information about the
contribution of the various components to the total dose measured by means of EPR dosimeters. For alanine dosimeters a good
agreement between experimental data and MC simulation have been achieved