SU‐E‐T‐230: Intracavitary in Vivo Dosimetry Based on Multichannel Real‐Time Fiber‐Coupled Radioluminescence (RL) and Optically Stimulated Luminescence (OSL) of Al2O3:C

Purpose: This work is aimed at developing a new probe to improve the accuracy of the dose delivery follow up in some Radiotherapy (RT) treatments that involve small fields like Irradiation Modulated RT (IMRT) and/or high dose gradients like Brachytherapy (BT) where the In Vivo Dosimetry (IVD) still remains challenging. Material and Methods: The OSL/FO (Optically Stimulated Luminescence/Fibre Optics) system designed by CEA LIST is composed of a multichannel reader and OSL OFS (Optical Fibre Sensors) incorporating dosimetric‐grade alumina crystals (Al2O3:C, grown in reducing atmosphere in the presence of carbon). Al2O3 :C crystals exhibit good sensitivity and small fading at room temperature. They are small (0.09 mm3), optically transparent, non‐hygroscopic, chemically inert. The OSL OFS are made of low‐Z materials (polymer, PMMA, alumina). They are electromagnetic‐immune, radiation‐resistant and transparent. The reader unit may deal with up to 15 channels with the use of an optical switch thus leading to an optimised cost‐per‐sensor ratio. During irradiation, part of free electrons promptly recombine and generate a RL (that provides realtime dose estimation) while another portion is kept stored. After irradiation, the crystal is remotely reset by laser light and the OSL is recorded to get the absorbed dose. Results and Conclusion: Within the French INTRADOSE project, the CEA‐LIST is currently developing small dosimetric catheters with the aim of measuring the intracavitary dose distribution, close to organs at risk. This yields the maximal dose and the source‐sensor distance. This device would allow checking that the source of 192Ir moves along the tubes, according to the treatment planning system. Metrological validations will be performed for both BT (prostatic cancer) and IMRT (head and neck cancer) treatments.