Iván Valastyán

Ethernet based distributed data acquisition system for a small animal PET

We report on the design of a small animal PET scanner being developed at our institutes. The existing setup is the first version of the miniPET machine consisting of four detector modules. Each detector module consists of an 8times8 LSO scintillator crystal block, a position sensitive photomultiplier, a digitizer including a digital signal processing board and an Ethernet interface board. There is no hardware coincidence detection implemented in the system and coincidence is determined based on a time stamp attached to every event by a digital CFD algorithm. The algorithm is implemented in the digital signal processing board and generates a time stamp with a coincidence resolution of less than 2 ns. The data acquisition system is based on Ethernet network and is highly scalable in size and performance

Performance test of the MiniPET-II small animal scanner according to the NEMA NU-4 standard

A full ring small animal PET camera (MiniPET-II) has been built in our institute as part of an R+D project. In this work we determined the performance parameters of the MiniPET-II scanner. The measurements and data evaluation for this purpose were based on the National Electrical Manufacturers Association (NEMA) NU-4 standards. The spatial resolution varies between 1.4 to 2.1 mm from central to 25 mm radial distances. The system sensitivity was 1.14%. The counting rate capability, expressed in noise equivalent counting rate (NEC), was shown to peak of over 55.1 kcps at 38.9 MBq using a mouse phantom. The scatter fraction with the same acquisition was 12.3%. Evaluations of image quality and quantization accuracy were also performed using the NEMA NU-4 required image-quality phantom and animal studies. The study proved that the MiniPET-II scanner has a good imaging capability and ability to perform real animal studies.

Development of an Improved Detector Module for miniPET-II

We present a new detector module developed for miniPET-II, the second generation of the miniPET small animal PET scanners. The improved module features new hardware components for better performance: LySO crystal material, increased number of crystal segments, Hamamatsu H9500 PSPMT, Xilinx Virtex-4 FPGA and Gigabit Ethernet. However, the principle of operation is the same: no hardware coincidence detection is implemented, data is acquired in list mode and transfered over an Ethernet network. The resulting new module is more suitable for full ring configurations.

Ethernet Based Distributed Data Acquisition System for a Small Animal PET

We report on the design of a small animal PET scanner being developed at our institutes. The existing setup is the first version of the miniPET machine consisting of four detector modules. Each detector module consists of an 8times8 LSO scintillator crystal block, a position sensitive photomultiplier, a digitizer including a digital signal processing board and an Ethernet interface board. There is no hardware coincidence detection implemented in the system and coincidence is determined based on a time stamp attached to every event by a digital CFD algorithm. The algorithm is implemented in the digital signal processing board and generates a time stamp with a coincidence resolution of less than 2 ns. The data acquisition system is based on Ethernet network and is highly scalable in size and performance

A Promising Future: Comparable Imaging Capability of MRI-Compatible Silicon Photomultiplier and Conventional Photosensor Preclinical PET Systems

We recently completed construction of a small-animal PET system—the MiniPET-3—that uses state-of-the-art silicon photomultiplier (SiPM) photosensors, making possible dual-modality imaging with MRI. In this article, we compare the MiniPET-3 with the MiniPET-2, a system with the same crystal geometry but conventional photomultiplier tubes (PMTs). Methods: The standard measurements proposed by the National Electrical Manufacturers Association NU 4 protocols were performed on both systems. These measurements included spatial resolution, system sensitivity, energy resolution, counting rate performance, scatter fraction, spillover ratio for air and water, recovery coefficient, and image uniformity. The energy windows were set to 350–650 keV on the MiniPET-2 and 360–662 keV on the MiniPET-3. Results: Spatial resolution was approximately 17% better on average for the MiniPET-3 than the MiniPET-2. The systems performed similarly in terms of peak absolute sensitivity (∼1.37%), spillover ratio for air (∼0.15), spillover ratio for water (∼0.25), and recovery coefficient (∼0.33, 0.59, 0.81, 0.89, and 0.94). Uniformity was 5.59% for the MiniPET-2 and 6.49% for the MiniPET-3. Minor differences were found in scatter fraction. With the ratlike phantom, the peak noise-equivalent counting rate was 14 kcps on the MiniPET-2 but 24 kcps on the MiniPET-3. However, with the mouselike phantom, these values were 55 and 91 kcps, respectively. The optimal coincidence time window was 6 ns for the MiniPET-2 and 8 ns for the MiniPET-3. Conclusion: Images obtained with the SiPM-based MiniPET-3 small-animal PET system are similar in quality to those obtained with the conventional PMT-based MiniPET-2.

Performance characteristics of a miniPET scanner dedicated to small animal imaging

An easy to scale up modular PET scanner was developed for imaging small animals. Energy resolution, spatial resolution and count rate performance were determined as system parameters. The configuration provided an average energy resolution of 19.6 % and the image resolution ranges was 1.5 to 2.3 mm in radial direction. The sensitivity of the miniPET was 1.08 cps/kBq as determined using a point source. In addition, results of rat brain scan performed with FDG are given to characterize imaging capability of the system. The displayed data document that the miniPET scanner supports good quality brain imaging of small animals

Probing the influence of SSZ-13 Zeolite pore hierarchy in MTO catalysis by NASCA microscopy and positron emission profiling

An understanding of the role of the hierarchical pore architecture of SSZ‐13 zeolites on the catalytic performance in the methanol‐to‐olefins (MTO) reaction is crucial to guide the design of better catalysts. We investigated the influence of the space velocity on the performance of a microporous SSZ‐13 zeolite and several hierarchically structured SSZ‐13 zeolites. Single catalytic turnovers, as recorded by nanometer accuracy by using stochastic chemical reactions (NASCA) fluorescence microscopy verified that the hierarchical zeolites contain pores larger than the 0.38 nm apertures native to SSZ‐13 zeolite. The amount of fluorescent events correlated well with the additional pore volume available because of the hierarchical structuring of the zeolite. Positron emission tomography (PET) using 11C‐labeled methanol was used to map the 2 D spatial distribution of the deposits formed during the MTO reaction in the catalyst bed. We used PET imaging to demonstrate that hierarchical structuring not only improves the utilization of the available microporous cages of SSZ‐13 but also that the aromatic hydrocarbon pool species are involved in more turnovers before they condense into larger multiring structures that deactivate the catalyst.

Hardware accelerated UDP/IP module for high speed data acquisition in nuclear detector systems

We propose an implementation of a data acquisition hardware description language module including an in-house soft MAC that is fast enough to exploit the bandwidth of gigabit Ethernet.

Distributed online coincidence detection using IP multicast for the miniPET-II detector

We report on a distributed online coincidence detection implementation that we have recently added to the miniPET-II small animal PET scanner. The implementation uses standard Ethernet and IP multicasting techniques, therefore no architectural changes were necessary to the existing system. For 2D reconstruction the implementation scales with the number of detectors in the system, so it can be used for larger ring configurations, too. The online coincidence detection makes the system suitable for real time imaging applications.

Evaluation detector module of the miniPET-3 small animal PET scanner

We report on the development of an evaluation detector module built for our miniPET -3 small animal PET scanner. The module is based on an LySO scintillation matrix exactly matching that used in miniPET-II (so that the performance of the two PET scanners is easier to compare), followed by a Silicon Photomultiplier (SiPM) matrix array. The front-end electronics is designed to be modular, so that different readout concepts can be evaluated and prototype-tested. The readout electronics is based on a system-on-module with Spartan-6 FPGA and Gigabit Ethernet connectivity. Different SiPM readout concepts were tested using the module, and based on the evaluation results one was selected for implementation and testing.