Improvement of retrospective sorting for artefact reduction in 4DMRI of the abdominal site
Year: 2019
Type: other
Abstract: u200bBeam profiling during patient treatment in hadrontherapy requires ultra-thin monitors to preserve the high beam quality. For detectors upstream in the line, a material budget as low as u223c15 u03bcm water-equivalent is needed. Besides, the current trend of dose escalation to treat highly resistant tumors implies challenging requirements to the monitor in terms of radiation hardness and dynamic range.We propose a new type of beam profiler, PEPITES, using secondary electron emission (SEE) and built with thin-film techniques and operating in the vacuum of the beam line. The beam is profiled by crossing thick nanometric patterns which emit the SEE signal. The patterns are deposited on polymeric membranes, which, in contrast with conventional systems like ionization chambers, are free from mechanical constraints and can be as thin as achievable. The thinness of the monitor disturbs very little the incident beam, which can then be delivered to the patient while keeping the profiler in the line, ensuring continuous monitoring. Also, it makes the energy loss very small, allowing the monitor to tolerate higher currents than existing systems without suffering from overheating problems. Besides, the absence of mechanical efforts on the membranes makes radiation damages of less consequence than with classical systems like ionization chambers allowing to extend the operation duration of the system.A simple prototype has been successfully operated with proton and alpha beams at the ARRONAX cyclotron in a wide range of currents (100fA - 100nA) and for several energies, validating the chosen technique1. Secondary electrons yields have been measured within the full therapeutic energy range at the ARRONAX cyclotron and the Orsay Protontherapy Center (CPO). At the same time, several irradiation campaigns with proton beams, electron beams, gamma sources have been conducted to evaluate the radiation damages with the deposited dose (up to 10^9 Gy). No significant effect on the detector is observed, which suggest great expectations about the profiler lifetime. Tests were performed using commercial ammeters, and an integrated electronics readout device is under development.The assets of PEPITES in the perspective of its use in hadrontherapy are numerous: good radioresistance for a long working duration, simple operations reducing installation and calibration times, a broad range of beam current and especially high flux allowing beam monitoring with dose delivery escalation. A fully working prototype is foreseen to operate at the ARRONAX cyclotron end 2020.
Language: English
Subfield: Radiation
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W3040910367