Multimodal Simulation of Large Area Silicon Photomultipliers for Time Resolution Optimization

The time response of a Silicon Photomultiplier (SiPM) depends on some of the intrinsic parameters of the sensor. Combining multiple and small SiPM instead of one with larger area will reduce the detector capacitance at electronic level, which can be translated into a lower signal jitter. This will improve the Single Photon Time Resolution (SPTR) of the sensor and the electronics and thus the Coincidence Time Resolution (CTR) of a PET system. This effect is studied using a combination of a physics simulation environment (GATE) and a commercial electrical simulator. GATE is an advanced opensource software developed by the international collaboration OpenGATE, dedicated to numerical simulations in medical imaging and radiotherapy. Accurate modelling of photon interactions with crystal surfaces is essential in optical simulations, but the existing UNIFIED model in GATE is often inaccurate, especially for rough surfaces. A new approach has been developed for GATE, named Davis Model. This method calculates the reflectance properties from the crystal topography previously measured with a surface scan device (AFM, CONFOCAL…). In combination with GATE, an electrical simulator is being used on this work to simulate the response of the SiPM and the front-end readout electronics. The aim of this work is to provide a framework that will enable a global optimization of the PET system that consider the scintillator, the sensor (sensor size, pixel pitch, dead area, capacitance) and the readout electronics (input impedance, noise, bandwidth, summation).