No abstract

a b s t r a c tIn this paper we illustrate the core technologies at the basis of the European SPADnet project (www. spadnet.eu), and present the corresponding first results. SPADnet is aimed at a new generation of MRI-compatible, scalable large area image sensors, based on CMOS technology, that are networked to perform gamma-ray detection and coincidence to be used primarily in (Time-of-Flight) Positron Emission Tomography (PET). The project innovates in several areas of PET systems, from optical coupling to single-photon sensor architectures, from intelligent ring networks to reconstruction algorithms. In addition, SPADnet introduced the first computational model enabling study of the full chain from gamma photons to network coincidence detection through scintillation events, optical coupling, etc.

In the recent years new digital photon counter devices (also known as silicon photomultipliers, SiPMs) were designed and manufactured to be used specifically in positron emission tomography (PET) scanners. These finely pixelated devices opened new opportunities in PET detector development, hence their application with monolithic scintillator crystals now are of particular interest. We worked out a simulation tool and a corresponding validation method to assist the optimization and characterization of such PET detector modules. During our work we concentrated on the simulation of SPADnet sensors and the LYSO:Ce scintillator material. Validation of our algorithms combines measurements and simulations performed on UV-excited detector modules. In this paper we describe the operation of the simulation method in detail and present the validation scheme for two demonstrative PET detector-like modules: one built of a scintillator with blackpainted faces and another with polished faces. By evaluating the results we show that the shape deviation of the average light distributions is lower than 13%, and the pixel count statistics follow Poisson distribution for both measurement and simulation. The calculated total count values have less than 10% deviation from the measured ones. K: Simulation methods and programs; Scintillators, scintillation and light emission processes (solid, gas and liquid scintillators); Gamma camera, SPECT, PET PET/CT, coronary CT angiography (CTA); Gamma detectors (scintillators, CZT, HPG, HgI etc) 1Corresponding author.

Silicon Photomultipliers have the ability to replace photomultiplier tubes when used as light sensors in scintillation gamma-ray detectors. Their timing properties, compactness, and magnetic field compatibility make them interesting for use in Time-of-Flight Magnetic Resonance Imaging compatible Positron Emission Tomography. In this paper, we present a new fully digital Single Photon Avalanche Diode (SPAD) based detector fabricated in CMOS image sensor technology. It contains 16x8 pixels with a pitch of 610x571.2 µm 2 .

In positron emission tomography (PET) slab scintillator crystals based detector modules are subject of intensive research, because all the three coordinates of the scintillation (point of interaction, POI) can be determined by them. Experimental evaluation of these detectors is done by using collimated γ-radiation where only two of the three spatial coordinates can be controlled. Alternatively, highly-detailed simulations can be used to evaluate detector performance as a function of POI, but their validation requires again experimental techniques. We propose a model validation method based on point-like, UV excitation of LYSO:Ce scintillators. The excited fluorescent pulses are identical in many respects to a scintillation excited by γ-photons. We discuss the details of our γ equivalent UV excitation arrangement, as well as compare the characteristics of the resulting fluorescence to those of scintillation light.