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Multiplexing many SiPMs to a single readout channel is an attractive option to reduce the readout complexity of high perfromance time of flight (TOF) PET systems. However, the additional dark counts and shaping from each SiPM cause significant baseline fluctuations in the output waveform, degrading timing measurements using a leading edge threshold. This work proposes a simple analog filtering network...
Time-of-flight (TOF) and depth of interaction (DOI) measurements are both important capabilities to improve clinical PET imaging. The combination of these two measurements has been shown to improve image quality and uniformity. Current high performance TOF DOI detectors have a high level of complexity, requiring cooling, pulse shape information or increased numbers of photosensors. This works describes...
We are developing a 3D positioning positron emission tomography (PET) detector module made up of dense stacks of 0.5 mm × 0.5 mm × 1.0 mm LYSO scintillation crystal elements coupled to position sensitive solid state photomultipliers (PS-SSPMs.) In this work, crystal arrays with four different types of outer face reflectors were tested to investigate the effect of outer reflectors on crystal identification...
Using time of flight (ToF) measurements for positron emission tomography (PET) is an attractive avenue for increasing the signal to noise (SNR) ratio of PET images. However, achieving fast timing resolution required for high SNR gain using silicon photomultipliers (SiPM) requires many resource heavy high speed readout channels. A method of multiplexing many SiPM signals into a single electronic channel...
In our previous works, we had investigated a pulse width modulation (PWM) based multiplexing readout for a detector that is built from dense stacks of LYSO scintillation crystal elements coupled to position sensitive solid state photomultipliers (PS-SSPMs). In our readout system, each of the PS-SSPM position channel signals are integrated for a set time to obtain event energy and position. In this...
PET/MRI systems require specialized PET detectors that can function inside of an MRI bore without interfering with MRI functionality. Ideally such a detector would be physically compact, low power, immune to interference from the MRI, and with minimal interference to the MRI, while preserving all PET timing, energy, and position information. Electro-optically coupled PET detectors, where the detector...
Time-of-flight (ToF) capabilities can significantly improve the signal-to-noise performance of clinical PET systems. To realize the full benefits of ToF the timing resolution of PET detectors must be as high as possible. End-readout of long thin scintillation crystals with photodetectors is widely employed, but is not optimal for timing measurements due to significant variations in optical photon...
3D printing is a developing technology that allows for the rapid fabrication of arbitrary three dimensional shapes. The technology is becoming increasingly affordable, accurate and accessible to researchers. As a result they are an attractive option for research groups to quickly and cheaply fabricate multi-modality imaging phantoms. In this work one 70 mm long, 50 mm diameter and two reusable 11...
Side-readout of scintillation light from crystal elements in PET is an alternative to conventional end-readout configurations, with the benefit of being able to provide fine depth-of-interaction (DOI) information and good energy resolution while achieving excellent timing resolution required for time-of-flight PET. In this study, the performance of discrete LYSO scintillation elements read out from...
This work presents a 16-channel time-to-digital converter (TDC) implemented in a field programmable gate array (FPGA) that can be used for a positron emission tomography (PET) detector with pulse width modulation (PWM) circuit readout. Simple tapped delay line methods using dedicated carry chain structures are used to measure short time intervals in conventional TDCs. We propose a TDC with more sophisticated...
The field of PET is moving toward systems comprising thousands of crystal elements coupled to thousands of semiconductor photodetector channels. Because of the large number of channels, developing methods for compact signal readout, while avoiding the need for new integrated circuit development is important. In this work a compact readout system for arrays of 0.5 mm × 0.5 mm × 1.0 mm LYSO crystal...
The results show that energy spectra and flood maps for sub-millimeter crystals can be produced using the gated integrator PWM circuit (see Fig.6). To measure the goodness of crystal identification the silhouette statistic was used [8]. The silhouette for each point i is given by: equation where a(i) is the average distance from i to every other point in the crystal, and b(i) is the average distance...
Combining PET with MRI in a single system provides clinicians with complementary anatomical and molecular information. However, current combined PET/MRI systems do not have time-of-flight (ToF)-PET capabilities due to certain design choices. We have developed an MRI-compatible front-end electronic system with fast timing PET capabilities. Our approach employs, a fast arrival time pickoff comparator...
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