Thermoluminescence in proton and fast neutron therapy beams

In photon radiotherapy, thermoluminescence dosemeters (TLD) are commonly used for in vivo dosimetry. In proton and neutron therapy, their use raises a particular difficulty since their responses vary significantly with the energy spectrum. With reference to Co-60, the response of CaF2:Tm (TLD-300) and (LiF)-Li-7:Mg,Ti (TLD-700) crystals was investigated in the 85 MeV proton beam and the p(65)+Be neutron beam produced at the cyclotron at Louvain-La-Neuve and used for therapy applications. In the proton beam, TLD dosemeters were irradiated in a phantom, at different positions in the unmodulated and modulated Bragg curve. In the fast neutron beam, TLDs were positioned inside the geometrical limits of the beam at different depths, and outside its limits behind five leaves of the multi-leaf collimator. peak height variation of glow curves was investigated and correlated with the variation of radiation quality.