A 100 ps CTR TOF-PET system constrains annihilation event location to just 1.5 cm along system LORs, thus enabling a 1.5-fold SNR improvement, relative to a system with 214 ps CTR, assuming a 40 cm diameter cylindrical phantom.Īchieving PET detectors with 100 ps CTR is possible by making use of recent innovations in both scintillation crystal, photodetectors, and readout electronics technologies. This work reports on efforts to develop detectors with 100 ps CTR using 10 mm length scintillation crystal elements that are required for efficient clinical imaging. State-of-the-art commercial TOF-PET systems report CTR values in the range of 214 – 400 picoseconds (ps), which correspond to an uncertainty in the annihilation photon pair point of emission of 3.2 – 6 cm along system detection lines-of-response (LORs). These improvements can be employed for better lesion visualization/quantification, lower injected radioactivity dose, or shorter scan duration, thus potentially expanding the role of PET imaging in disease characterization. Incorporating 511 keV annihilation photon TOF information enables a significant boost in reconstructed image signal-to-noise ratio (SNR), which has a similar effect as enhancing PET system sensitivity. Results show CTR values of 102.0☐.8, 100.2☑.2, 97.3☑.8 and 95.0☑.0 ps full-width-half-maximum (FWHM) with non-calibrated energy resolutions of 10.2☑.8, 9.9☑.2, 7.9☑.2, and 8.6☑.7 % FWHM for the Teflon, ESR (without grease), BaSO 4 (without epoxy) and TiO 2 paint treatments, respectively.ĭuring the past decades there have been considerable efforts towards advancing annihilation photon pair coincidence time resolution (CTR) for time-of-flight positron emission tomography (TOF-PET). For the experimental set-up, we made use of 3×3×10 mm 3 fast-LGSO:Ce scintillation crystal elements coupled to an array of silicon photomultipliers (SiPMs) using a novel “side-readout” configuration that has proven to have lower variations in scintillation light collection efficiency and transit time to the photodetector. ![]() To study the effects of the reflector covering the scintillation crystal element on CTR, we have tested the performance of four different reflector materials: Enhanced Specular Reflector (ESR) –coupled with air or optical grease to the scintillator Teflon tape BaSO 4 paint alone or mixed with epoxy and TiO 2 paint. A critical parameter to understand is the optical reflector’s influence on scintillation light collection and transit time variations to the photodetector. The goal of the present work is to build a novel TOF-PET system with 100 picoseconds (ps) CTR, which provides an additional factor of 1.5–2.0 improvement in reconstructed image SNR compared to state-of-the-art TOF-PET systems which achieve 225 – 400 ps CTR. The CTR is determined by several factors including the intrinsic properties of the scintillation crystals and photodetectors, crystal-to-photodetector coupling configurations, reflective materials, and the electronic readout configuration scheme. The degree of SNR improvement from this TOF capability depends on the coincidence time resolution (CTR) of the PET system, which is essentially the variation in photon arrival time differences over all coincident photon pairs detected for a point positron source placed at the system center.
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