Image Resolution Enhancement Using Time-of-Flight-Based Backscatter Rejection in Compton Camera

This study presents a technique to enhance Compton camera imaging used for radioactive source localization in security applications. A key issue in Compton imaging is "backscattering events," where gamma-ray interactions are misordered—such as when the absorber records a hit before the scatterer—leading to incorrect Compton cone reconstruction and image artifacts. To address this, the research applies the Time-of-Flight (TOF) principle to determine the correct interaction sequence.A detector system comprising GFAG scintillators, SiPMs, and a custom ASIC/DAQ setup achieves a 296 ps coincidence time resolution, sufficient to resolve 4.4 cm-scale interaction order. TOF values are calculated per event after correcting for systematic effects, allowing identification and rejection of backscattering events. Applying this TOF-based filtering significantly improves the signal-to-noise ratio. The resulting data, processed with the MLEM algorithm, yields an angular resolution (ARM) of 13.3°–16.5° (FWHM), aligning well with Geant4 simulations. This demonstrates TOF filtering as an effective method for enhancing Compton imaging quality.