A fast detection system for Prompt Gamma Time Imaging

Le résumé fourni par la source

In order to ensure the consistency of treatment delivery and treatment planning in hadrontherapy, we propose an on-line range monitoring technique called Prompt Gamma Time Imaging (PGTI) that is based on the exclusive measurement of Prompt Gamma Time-Of-Flight. For this, we are developing a high temporal resolution, multi-channel, gamma detector (TIARA for Tof Imaging ARrAy) read in time coincidence with a ion beam monitor [1]. The gamma modules are based on pure Cherenkov radiators (PbF2) coupled to SiPMs in order to optimize the time response and minimize the sensitivity to neutron background. Thanks to their small volume (~1 cm3) they can be placed all around the target/patient while allowing irradiations from multiple angles. A dedicated spatial reconstruction algorithm is also developed to combine the response of the 30 TIARA modules. PGTI accuracy is a compromise between the number of Prompt Gamma events acquired and the system time resolution. According to previous Monte Carlo simulations, we expect to reach a spatial accuracy of 1 mm at 2 σ under the hypothesis of a 235 ps FWHM coincidence time resolution and 108incident protons [2]. In this work, we present the design and performances of an 8-channels prototype. With 63 MeV protons from the Medicyc cyclotron of the Centre Antoine Lacassane (CAL) in Nice, we obtained a coincidence time resolution of 254 ps FWHM, and we achieved an accuracy of 2 mm (at 2 σ) on the measurement of proton range with 3000 PGs, corresponding to the statistics expected for an irradiation spot of 107protons. More recently, the TIARA response was tested through the irradiation of an anthropomorphic head phantom at the S2C2 synchro-cyclotron of the CAL, with 100 MeV protons directed at one of the sinuses. The two acquisitions performed with the sinus either empty (air) or filled with ultrasound gel resulted in significantly different Time-Of-Flight distributions, thus proving TIARA’s ability to detect anatomical changes.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.