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Research conducted in the framework of the Jagiellonian-PET (J-PET) project aims to develop a cost-effective total-body positron emission tomography scanner. As a first step on the way to construct a full-scale J-PET tomograph from long strips of plastic scintillators, a 24-strip prototype was built and tested. The prototype consists of detection modules arranged axially forming a cylindrical diagnostic chamber with the inner diameter of 360 mm and the axial field-of-view of 300 mm. Promising perspectives for a low-cost construction of a total-body PET scanner are opened due to an axial arrangement of strips of plastic scintillators, which have a small light attenuation, superior timing properties, and the possibility of cost-effective increase of the axial field-of-view. The presented prototype comprises dedicated solely digital front-end electronic circuits and a triggerless data acquisition system which required the development of new calibration methods including time, thresholds, and gain synchronization. The system and elaborated calibration methods, including first results of the 24-module J-PET prototype, are presented and discussed. The achieved coincidence resolving time equals to ${\mathrm {CRT}}=490\pm 9$ ps. This value can be translated to the position reconstruction accuracy $\sigma (\Delta l) =18$ mm, which is fairly position independent. [ABSTRACT FROM AUTHOR]

Currently, the prevailing high-resolution Positron Emission Tomography (PET) detector architecture consists of pixelated scintillating crystals coupled to a photosensitive layer, such as position sensitive photomultiplier tubes (PS-PMTs) or silicon photomultiplier (SiPM) arrays. In such detector designs, a light guide layer is commonly used between the finely segmented scintillating crystal array and coarsely segmented photosensitive layer to disperse scintillation light over several elements of the photosensitive layer. Such detectors typically rely on some form of analog signal multiplexing to minimize the number of readout electronics channels and employ Center-of-Gravity (CoG) approach to calculate the positions of gamma-ray interactions. In this article, we report on the Truncated Center of Gravity (TCoG) and Raised-To-the-Power (RTP) algorithms for calculation of gamma photon scintillation position as applied to our newly developed small-scale prototype PET system consisting of a pair of opposing detectors based on $24\times24$ LYSO scintillation crystal matrices and $8\times 8$ SiPM arrays with 64:16 multiplexed readout. The major notable advantage of using TCoG or RTP algorithm in contrast to basic CoG is shown to be their independence of photosensor gain variations. An improvement in the calculation of scintillation positions is demonstrated both for TCoG and RTP algorithms, the Field of View (FOV) distortion inherent to CoG reconstruction is eliminated. On average, the Peak-to-Valley Ratio (PVR) is increased at least by a factor of 2.25. The energy resolution for the considered small-scale PET prototype is ~13.5% when using CoG, TCoG, or RTP reconstruction algorithms. [ABSTRACT FROM AUTHOR]

The presented models for silicon photomultiplier (SiPM) detectors in literature have been mainly used to study fast light pulses. In this paper, a comprehensive dynamic model is proposed to investigate the output signal of a SiPM exposed to intensity-modulated lights (with sine-wave modulation). A procedure is also proposed to simulate this model. Using the proposed model, the SiPM behavior is examined under various frequencies and intensities of lights in simulation. Then, fluorescence lifetime (FLT) measurement in the frequency domain is discussed. Finally, the simulation results are compared with the experimental results which are extracted from an experiment set up employing two SiPMs exposed by excitation and emission lights. [ABSTRACT FROM AUTHOR]