High Sensitivity and High Resolution Dynamic Brain-Dedicated TOF-DOI PET Scanner

We are presenting a novel design of a high performance brain dedicated PET scanner which focuses on optimizing imaging performance in the whole brain, as well as in head and neck, through simultaneous high resolution and high sensitivity. This is realized using a sensitivity-optimized scanner design composed of an elliptical cylinder that follows the shape of the human head, together with added front and back panels for increased coverage. System simulations with 15 mm LYSO crystals show as high as 23% sensitivity in the cerebral cortex region and 16% sensitivity in the field of view (FOV) center. The unconventional high angular coverage geometry requires detectors with good depth of interaction (DOI) capability to reduce image blurring at the FOV edge. Furthermore, the incorporation of time of flight (TOF) information for a small FOV like the brain requires timing resolution beyond that of standard PET detectors. Design targets for our detector are 1.5 mm intrinsic detector resolution, 3 DOI levels and <150 ps FWHM Coincidence Timing Resolution (CTR) throughout the detector volume. To meet these requirements, we are developing a detector concept composed of 3 layers of staggered LYSO scintillator arrays, with one-to-one coupling between the first crystal layer and the photodetector array. Light transport simulations show that straightforward DOI positioning based on counting the SiPM signals above a single threshold can be achieved with this detection scheme. In addition, the jitter in the arrival times of the first scintillation photon to reach the photodetector results in CTR<150 ps regardless of the scintillator surface properties. To maintain this low CTR when including optical sensor and electronics, we are proposing to couple the scintillators to a new Integrated Light Sensor and ASIC (ILSA) module that by design adds minimal time jitter to the light signal. This is achieved through co-design of high PDE and low pitch SiPM arrays (FBK) and low noise ASICs (Univ. Barcelona).