Comparison of UV-enhanced SiPM technologies for estimating 511 keV photon arrival time using BGO Cherenkov Luminescence

Time-of-flight (TOF) is a method to boost reconstructed image signal-to-noise ratio in positron emission tomography (PET); the SNR gain increases as detector coincidence time resolution (CTR) improves. It is also desirable to control detector costs, especially when developing long axial field of view PET systems. With these two goals in mind, it has been proposed to exploit the prompt luminescence, predominantly Cherenkov light, in the scintillation crystal BGO, to estimate the annihilation photon arrival time for PET detectors. However, properly identifying the relatively low number of Cherenkov photons generated per interaction event in BGO is not easy, requires low noise photodetectors, fast readout electronics, and accurate signal processing techniques. Since Cherenkov photons are produced in the ultra-violet (UV) realm, photosensor technology with enhanced performance in the UV region is essential for best performance. In this work we have evaluated and compared the performance of three different UV-enhanced silicon photomultiplier (SiPMs) coupled to 3 × 3 mm2 BGO scintillators ranging from 3 mm to 15 mm length, and two different readout circuits. State-of-the-art data postprocessing methods have been employed for CTR estimation, consistently yielding CTR values < 300 ps full-width-at-half-maximum (FWHM) for all crystal lengths studied. To our knowledge, this is the first work comparing these UV-SiPM models under the same conditions.