Bragg Peak Monitoring in Carbon-Ion Radiotherapy Using a Dual-Head LYSO-SiPM In-Beam PET System

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Accurate verification of the Bragg peak is critical for ensuring treatment precision in carbonion radiotherapy (CIRT), especially for large or complex tumors. In this study, we developed and evaluated a dual-head in-beam PET system based on LYSO scintillators and SiPM arrays for real-time monitoring of carbon-ion beams. Beam experiments were conducted at the Wuhan Heavy Ion Hospital using monoenergetic carbon-ion beams ranging from 120.12 to 280.56 MeV/u. The PET system, featuring a 20 cm inter-head gap and high-resolution timing electronics, collected singles data during spill-off periods to isolate positron annihilation events. Energy spectra confirmed a distinct 511 keV peak with minimal background interference. PET images reconstructed using the MLEM algorithm showed clear correlations with Bragg peak positions for both in-beam and off-beam phases. These findings demonstrate the system's potential for accurate, non-invasive verification of dose deposition during CIRT and support its integration into clinical workflows for improved treatment monitoring.