Improving the Cherenkov Based PET Performance Using Multi-Layer Detectors

Positron emission tomography (PET) images can be improved by including measurement of time-of-flight (TOF) information in image reconstruction. The accuracy of the TOF measurement is currently limited by the time response of the scintillator crystal. One open possibility to develop new devices is to search for new materials with faster light emission mechanisms such as the Cherenkov light emitted by electrons moving in a material with velocities exceeding the speed of light in the material. This enables excellent time resolution. On the other hand, the travel time spread of photons inside crystals of sufficient length for PET application represents a fundamental limitation for the TOF resolution. One possibility to improve the timing without affecting gamma stopping power is to use a multi-layer detector geometry. In this work we have explored a multi-layer detector for Cherenkov PET using annihilation gammas from a sodium source (Na-22). When incorporating silicon photomultiplier (SiPM) photodetectors, Cherenkov PET detectors could be realized at a very competitive price. Due to their compact size, SiPMs also enable the construction of a multi-layer detector.