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Program Information

Development of a Compton Camera for Online Range Monitoring of Laser-Accelerated Proton Beams


K Parodi

P Thirolf1, S Aldawood1,2, C Lang1, K Parodi1*, (1) Ludwig-Maximilians-Univ. Muenchen, Garching, Germany, (2) King Saud University, Riyadh, Saudi Arabia

SU-E-I-80 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:
Development of a versatile detector system primarily designed for online range monitoring of proton beams generated via the novel technique of particle acceleration from high-power, short-pulse lasers to be used in bio-medical applications.

Methods:
While so far mostly offline diagnostics tools are used in this context, we aim at developing a technique based on the position-sensitive detection of prompt gamma rays emitted from nuclear reactions between the proton beam and the biological sample. For this purpose, we develop a Compton camera capable to track not only the Compton scattered primary photon, but also the secondary Compton electron.

Results:
Extensive simulation studies resulted in an optimized design of the Compton camera based on a LaBr₃(Ce) scintillation crystal (50x50x30 mm³ block crystal, read out by a multi-anode PMT) acting as absorber, preceded by a stack of 6 double-sided silicon strip detectors as scatterers (500 μm thick, 128 strips/side, pitch 390 μm). From the design simulations an angular resolution of <= 2⁰ (at 2-6 MeV) and a source image reconstruction efficiency of 10⁻³ -10⁻³ (at 1-5 MeV) can be expected. The LaBr₃ crystal has been characterized with laboratory sources, resulting in a time resolution of 540 ps and a position-dependent energy resolution (best in the central region). Using a collimated source the point-spread function was determined from the pixelated light distribution, yield a (preliminary and by software optimization improving) spatial resolution of < 3mm.

Conclusion:
The Compton camera based approach for prompt-γ detection from nuclear interactions of therapeutic ion beams offers very promising perspectives for online range monitoring. An arrangement of several camera modules could even be used in a γ-PET mode to additionally detect delayed annihilation radiation from positron emitters in the irradiation interrupts (with improved performance in the presence of an additional third (prompt) γ (as e.g. in ¹⁰C, ¹⁴O).

Funding Support, Disclosures, and Conflict of Interest: Funding support via German Science Foundation: DFG Cluster of Excellence MAP (Munich Centre for Advanced Photonics)

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