An 8×16-pixel 92kSPAD time-resolved sensor with on-pixel 64ps 12b TDC and 100MS/s real-time energy histogramming in 0.13µm CIS technology for PET/MRI applications

Positron-Emission Tomography (PET) is a nuclear imaging technique that provides functional 3-dimensional images of the body, finding its key applications in clinical oncology and brain-function analyses. The typical PET scanner is composed of a ring of scintillator crystals that absorb gamma rays and emit photons as a result, coupled to photon-sensing devices. The photons hit the sensors with a certain spread in space and time, depending on the material and geometry of the crystals. The sensors must then estimate the energy, the time of arrival (ToA), and the axial position of incoming gamma rays. Most commercially available scanners use photomultiplier tubes (PMTs), which are sensitive to magnetic fields, as the sensing element, making the integration of these systems with Magnetic-Resonance Imaging (MRI) impossible. A significant amount of research has focused on replacing PMTs with solid-state detectors, such as Silicon photomultipliers (SiPMs) [1], which can be integrated with MRI while maintaining the high-sensitivity of PMTs.