Pushing the Limit of BGO-based Dual-ended Cherenkov PET Detector Through Photon Transit Time Correction

The rising production costs of commonly used lutetium-based fast scintillators and the development of silicon photomultipliers technology have made BGO a promising candidate for time-of-flight positron emission tomography (TOF PET) detectors due to its ability to generate prompt Cherenkov photons. However, using BGO as a hybrid scintillator presents challenges due to low photon statistics and a distribution that does not conform well to a single Gaussian. To mitigate this, a proposal was made to increase the likelihood of detecting the first Cherenkov photons by positioning two photosensors in opposition at the entrance and exit faces of the scintillator [1]. In the other hand, compensating for the photon transit time spread is known to enhance the timing performance of the dual-ended BGO Cherenkov TOF PET detector [2]. A 3 × 3 × 15 mm
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unpolished BGO sample was prepared and tested. The high-frequency dual-ended BGO detector was implemented and coincidence events were acquired against a 3 × 3 × 3 mm
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LYSO:Ce:Mg reference detector. The timing performance of dual-ended BGO detectors were analyzed using bottom, top, meantime, and adaptive timestamp methods. Through a depth-of-interaction based (DOI-based) correction of photon transit time spread, we demonstrated a further improvement in timing resolution of dual-ended BGO-based Cherenkov TOF PET detector with adaptive arrival time pickoff. The use of a dual-ended configuration resulted in a significant improvement in timing resolution compared to a single-ended readout configuration, particularly in terms of FWTM value. Although polishing the crystal surface was still favorable in terms of FWHM value, compensating for photon travel time by taking advantage of DOI information from unpolished crystals with relatively higher light loss enabled further enhancement in timing performance the polished crystals.