Time-of-Flight Collimated- and Compton-Cameras Development for Ion Beam Therapy Monitoring
Résumé
In ion beam therapy, the increased energy deposition of ions towards the finite range in tissue (Bragg peak) allows a precise dose delivery.With the aim of optimizing the ion treatment effectiveness, a strict range monitoring is mandatory: different solutions have been explored, but an online treatment check is still a challenge.The detection of the prompt-gammas (PG) emitted during treatments has proven its potential in the ion range control in real time (Min et al 2006, Testa et al 2008). The falloff of the PG profile (1D distribution along the beam direction) can be measured with millimetrical precision and correlated to the dose distribution thanks to collimated cameras. Compton cameras are also under study to bring 2D – 3D information on PG distributions. Moreover, the application of the Compton camera in the nuclear medicine field, namely for Single Photon Emission Computer Tomography (SPECT).The development of two prototypes is ongoing in France thanks to the collaboration of five institutions: IPNL (Lyon), CREATIS (Lyon), LPC (Clermont-Ferrand), CPPM (Marseille) and LPSC (Grenoble).The collimated camera design consists of a multi-slit collimator and a segmented absorber made up of 96 BGO streaked blocks, with a position reading pitch of 4 mm in both directions. The same absorber is employed for the Compton camera prototype, together with a stack of 7 double-sided silicon strip detectors (1.41 mm pitch) used as scatter.The use of Time-Of-Flight technique is foreseen for both prototypes in order to maximize the signal (PG) to background (neutron) ratio. A beam tagging hodoscope is then under construction, consisting of two planes of 2 x 128 perpendicular scintillating fibers, read by 64-channel photomultipliers.The three detector components are being tested in the different partner institutions.This contribution will present an overview of the status and perspectives of emission imaging techniques carried out by the collaboration.