J. Imrek

Development of an FPGA-based data acquisition module for small animal PET

We report on the design of a data acquisition (DAQ) module for a small animal PET camera developed at our institutes. During the design an important guideline was to develop a system which is built up from strictly identical DAQ modules, and which has no built-in hardware limitation on the maximum number of modules. The developed DAQ module comprises of an LSO scintillator crystal block, a position sensitive PMT, analog signal conditioning circuits, a digitizer, an field programmable gate array (FPGA) for digital signal processing, and a communication module through which the collected data are sent to a cluster of computers for postprocessing and storage. Instead of implementing hardware coincidence detection between the modules, we attach a precise time stamp to each event in our design, and the coincidence is determined by the data collecting computers during postprocessing. The digital CFD algorithm implemented in the FPGA gives a time resolution of 2 ns FWHM for real detector signals

Development of an FPGA-Based Data Acquisition Module for Small Animal PET

We report on the design of a DAQ module for a small animal PET camera developed at our institutes. During the design an important guideline was to develop a system which is built up from strictly identical DAQ modules, and which has no built-in hardware limitation on the maximum number of modules. The developed DAQ module comprises of an LSO scintillator crystal block, a position sensitive PMT, analog signal conditioning circuits, a digitizer, an FPGA for digital signal processing and a communication module through which the collected data is sent to a cluster of computers for post processing and storage. Instead of implementing hardware coincidence detection between the modules we attach a precise time-stamp to each event in our design, and the coincidence is determined by the data collecting computers during the post processing. The digital CFD algorithm implemented in the FPGA gives a time resolution of 2 to 3 ns FWHM for real detector signals

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.

Experimental scanner setup from miniPET II detector module

The PET technique is widely used in human clinical studies and recent developments of image resolution has made it suitable for small animal research. The second generation of our PET scanner consists of 12 detector modules and has a field of view large enough to image mice and rats. Parameters of the incoming data are extracted by Digital Signal Processing in the detector modules and a System-on-Module is used to transmit the data through an Ethernet network for storage and reconstruction. The experimental scanner setup described in this paper was constructed in order to investigate the applicability of the developed detector modules in a full ring small animal PET camera. The preliminary results of the system are also presented.

Internals and evaluation of the miniPET-II detector module

We report on the architecture of the system-on- module (SoM) developed by our group for miniPET-II, the second version of our small animal PET scanner. The paper describes the hardware and software implementation details of the SoM we realized inside the miniPET-II detector module, the embedded Linux operation system, and the the initial results of bandwidth test measurements on the assembled SoM. Detailed description is given on the interfacing of the updated miniPET IP Core to the SoM, on the efficient data transfer method that implements device-to-device DMA transfer, and on the usage of User Datagram Protocol (UDP/IP) for high speed data transfer.

Novel time over threshold based readout method for MRI compatible small animal PET detector

Combined PET-MRI scanners start a new era in medical imaging. However the development of MRI compatible PET detector module is a challenging task. SiPM sensors are insensitive to magnetic field and constitute a promising solution. A drawback is the high dark current. A readout concept for SiPM based small animal PET detector module is presented in this paper. The results show that the readout of the SiPM is possible using only four ADC channels and the position map is comparable to the ideal solution. The detector modules based on the method are feasible solution for MRI compatible PET scanners.