Multichannel dosimeter and α-Al2O3:C Optically Stimulated Luminescence (OSL) fiber sensors for use in Radiation Therapy - evaluation with photon beams

A multichannel OSL Fibre Optic dosimeter based on Optically Stimulated Luminescence (OSL) of alumina is proposed for on-line In Vivo Dosimetry (IVD) in Radiation Therapy (RT). Two types of dosimetric-grade Al₂O₃:C crystals are compared and show different behavior according to manufacturing process. Metrological validations have been performed with a Saturne 43 LINAC in reference conditions at CEA LIST LNHB (French Ionizing Radiation Reference Laboratory). The dose response of OSL integrals under photon beam irradiation (6, 12 and 20 MV) show sublinearity behavior modeled by second-order equations and exhibit a small energy dependence (between 0.7% and 1.4%), explained by a modified intermediate cavity model adapted to a LINAC photon spectrum. Preclinical tests at Institut Gustave Roussy (IGR) prove that a proper design for a PMMA build-up cap leads to a low dependence vs photon beam orientation (± 1.5 % and ± 0.9 %) and vs field size in view of surface measurements.