A magnetic field compatible readout circuit for enhanced coincidence time resolution in BGO Cherenkov radiation-based...

Developing time-of-flight positron emission tomography/magnetic resonance imaging (TOF-PET/MRI) detectors that exploit prompt Cherenkov photons from bismuth germanate (BGO) crystals for estimating 511 keV photon arrival time.

To present a low-noise, high-speed electronic readout circuit design for BGO-based TOF-PET detectors that achieves enhanced coincidence time resolution (CTR) in presence of a strong magnetic field.

The CTR of a BGO-based TOF-PET test detector employing a high-speed, low-noise electronic readout chain was evaluated in a strong magnetic field produced by a permanent magnet placed directly on top of the circuit. For these experiments, which exploit Cherenkov radiation for precise measurement of annihilation photon time arrival time difference, a point source of ²²Na was positioned between a pair of 3 × 3 × 15 mm³ polished BGO crystals wrapped in Teflon tape and optically coupled to 3 × 3 mm² ultra-violet (UV)-sensitive silicon photomultipliers (SiPMs).

By incorporating both Cherenkov (prompt) and standard (slow) luminescence components, 283 ± 8 ps and 275 ± 10 ps full-width-half-maximum (FWHM) CTR were achieved without and with the permanent magnet present, respectfully. These values improved to 236 ± 4 ps and 216 ± 17 ps FWHM when only the Cherenkov components of the timing signal (events with the fastest rise time) were considered.

Results indicate we have designed a high-performance readout circuit that achieves significantly the same CTR in BGO with or without a strong magnetic field present. This further demonstrates that UV SiPMs can effectively operate in a strong magnetic field while remaining highly advantageous for detecting Cherenkov radiation, thus highlighting their potential to be used in BGO-based TOF-PET/MRI scanners.