50-Channel Ionoacoustic Sensor for 60 MeV Proton Beam Characterization in Hadron Therapy Applications

This paper presents the design of a piezoelectric multichannel sensor optimized for sensing weak ionoacoustic signals generated at the Bragg peak (BP) of pulsed proton beams, with interesting possible applications in real-time monitoring of oncological hadron therapy treatments. To overcome current single-channel detector limitations and acquire the weak acoustic signals of clinical scenarios (60–200 MeV proton energy and few mGy dose deposition), the hereby presented detector overcomes the state-of-the-art approach (based on time-domain correlation i.e., averaging different beam pulses) by using spatial correlation (i.e., averaging signals from different detector channels) to increase the SNR without increasing the delivered dose. The detector design is tailored around the experimental environment characteristics (signal amplitude, signal frequency, relative BP-detector position) of a clinical proton beam (60 MeV, 2 mGy/pulse dose deposition). The detector design was characterized by a complete cross-domain simulation of the physical (proton beam), acoustic (wave propagation) and electrical (sensor and electronics frequency response and noise) environments. It achieves a clear 10 dB single-pulse SNR (2 mGy total dose) and allows to locate the BP with 125 μm precision (< 3% w.r.t. the particle range). Finally, the detector was experimentally validated by a piezoelectric acoustic testbench and has shown the capability to localize an acoustic source in 2D with sub-millimeter accuracy by using a multilateration-based BP detection algorithm.