Investigating the Timing Behavior of Compton Scattering in BGO for Time-of-Flight PET.

Area of Science:

• Medical Imaging Physics
• Materials Science in Nuclear Detectors
• Positron Emission Tomography

Background:

• Bismuth germanate (BGO) is a promising material for hybrid Cherenkov/scintillation time-of-flight positron emission tomography (TOF-PET) detectors.
• Pixelated BGO arrays in TOF-PET introduce inter-crystal scattering (InterCS) events, impacting timing accuracy.

Purpose of the Study:

• To experimentally investigate the impact of InterCS on BGO Cherenkov timing in pixelated TOF-PET detectors.
• To quantify the timing resolution degradation caused by InterCS events.
• To evaluate the effect of InterCS on prompt photon yield.

Main Methods:

• Utilized a dual-pixel BGO detector with segmented SiPM readout.
• Classified events into full-energy deposition (FED), InterCS, and penetration types using energy-weighted positioning.
• Validated event classification with GATE simulations.
• Analyzed timestamp selection strategies for InterCS events.

Main Results:

• InterCS events resulted in a coincidence timing resolution of 221 ps FWHM, compared to 184 ps FWHM for FED events.
• Prompt photon yield decreased measurably for InterCS events (4.73 photons/ns vs. 5.76 photons/ns for FED).
• Over 25% of experimentally identified FED events involved intra-crystal scatter (IntraCS).

Conclusions:

• InterCS significantly degrades timing resolution in pixelated BGO TOF-PET detectors.
• Time-aware, per-pixel timestamping strategies are essential for mitigating scatter effects.
• Addressing InterCS is critical for achieving optimal timing performance in BGO-based TOF-PET systems.