-
[show abstract]
[hide abstract]
ABSTRACT: A flexible, extensible, high-speed architecture, called Quicksilvertrade and specifically geared to the requirements of small animal imaging, has been developed. The architecture is composed of ring-based event processing modules (EPMs) with nearest neighbor, high-speed digital communication transmitting event packets via a "store and forward" concept. Each EPM is capable of transmitting up to 15.6M events/sec to other EPMs. Coincidence determination is performed at the EPM level around the "ring". This distributes the load and eliminates the need for a separate coincidence processor. Each EPM is capable of transmitting up to 1.9M coincidence events/sec to an event routing subsystem (ERS) for acquisition and processing. The ERS has 2 transport interfaces for acquiring events: an IEEE 1394A interface and a PCI interface. The IEEE 1394A interface can support up to 5.3M events/sec and the PCI interface can support up to 16.7M events/sec. Thus this architecture provides a new level of capability for small animal PET imaging, but is also extremely well suited for PET research, single photon emission computed tomography (SPECT) imaging, and use with X-ray CT and magnetic resonance imaging (MRI).
Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006
-
[show abstract]
[hide abstract]
ABSTRACT: The QuickSilver Event Processing Module (EPM), an electronics module used in Siemens Inveon PET and SPECT systems, provides data acquisition, event processing and coincidence determination functions. Custom mixed-signal CMOS ASICs and high speed ADCs are utilized to provide the front-end analog portion of the data acquisition. A high performance FPGA provides the digital portion of the data acquisition running at 100 MHz, the subsequent event processing, and the coincidence determination. The high performance FPGA also provides multiple high speed serial data channels for external interconnection. This interconnection allows the module to be replicated as needed in a distributed parallel processing architecture to provide flexible, high performance, PET and SPECT imaging. The module also provides controllable high voltage needed to bias detectors. A 64 channel, LSO based PET system built using 16 EPMs yielded 1.22 ns FWHM system timing and better than 14% energy resolution.
Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006
-
[show abstract]
[hide abstract]
ABSTRACT: Time alignment is critical to the operation of high performance PET systems. Optimizing the countrate performance of a given system requires proper timing to minimize the effects of random events as early in the datastream as possible to reduce electronic deadtime. Siemens Inveon PET systems high countrate performance is made possible by their exceedingly tight timing tolerance of 1.22 ns FWHM, allowing the use of an optimal 3.5 ns coincidence window. This paper describes the hardware capabilities used to align the system as well as the processing techniques used to perform the alignment.
Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006
-
[show abstract]
[hide abstract]
ABSTRACT: The Quicksilver Event Routing Subsystem (ERS) is a new CompactPCI card developed as part of a new high performance data acquisition platform from Siemens Molecular Imaging (Knoxville, TN). The card's main purpose is to route event data from the Quicksilver Event Processing Modules (EPM) out to either IEEE 1394A or PCI data collection channels. To accomplish this task, an ERS uses eight 2.0 gigabit/second serial links to the EPM backplane to receive incoming data, an outgoing 32 megabyte/second IEEE 1394A link, and an outgoing PCI interface capable of 200 megabytes/second. The card's secondary purpose is to facilitate insertion of real-time system tagword information into the outgoing data stream such as time marks, physiological gating events, and motion axis positions. The ERS is built around a Xilinx Virtex II Pro FPGA which performs on-the-fly event packet prioritization, format translation, and flow control. This architecture allows the ERS to process up to 33 million single or coincident events per second while guaranteeing the integrity of tagword packets.
Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006
-
[show abstract]
[hide abstract]
ABSTRACT: Standard whole-body PET/CT protocols collect PET emission data for a sequence of discrete, overlapping bed positions. An alternative acquisition mode in which the patient bed moves continuously through the scanner has some significant advantages, including uniform axial signal-to-noise, elimination of resolution artifacts by sampling continuously in the axial direction, and a reduction in both noise from detector normalization and artifacts from small patient movements. To validate this approach, continuous bed motion acquisition has been implemented on a high resolution, 16-slice LSO PET/CT scanner (CPS Innovations, Knoxville, TN). The emission data are acquired in list mode with the bed moving at a constant velocity in the range 0.3-0.7 mm/s for a total scan time in patients of around 20 minutes covering an axial extent of 36-84 cm. The absolute position of the bed is read and inserted directly into the list mode data stream. Following acquisition, the emission data are rebinned into a fully 3D data set and reconstructed using a 3D OSEM algorithm. Continuous movement of the patient bed yields uniform signal-to-noise throughout the axial imaging field. For short imaging times, the bed movement in the standard acquisition becomes a significant fraction of the total scan time and continuous bed motion acquisition offers a more efficient alternative. Results are presented for some representative patient studies with both step-and-shoot and continuous bed motion acquisition.
Nuclear Science Symposium Conference Record, 2004 IEEE; 11/2004
-
J.T. Yap,
N.C. Hall,
D.W. Townsend,
J.S. Wall,
A. Solomon,
J.W. Kabalka,
S.J. Kennel, D.F. Newport,
S.B. Siegel,
D. Bailey,
A.M. Smith,
R.E. Nutt
[show abstract]
[hide abstract]
ABSTRACT: Recent advances in multi-detector CT design have enabled isotropic sub-millimeter spatial resolution. Although dedicated small animal CT scanners have been developed, the latest generation of high-performance clinical CT scanners may have sufficient spatial resolution for the purposes of small animal imaging. We have investigated the use of a clinical 16-slice PET/CT scanner in combination with the microPETreg scanner for rodent imaging. A method for co-registering PET/CT and microPET images was developed to improve the anatomical localization of PET uptake and perform attenuation and scatter correction. CT and PET visible fiducial markers containing a <sup>68</sup>Ge point source are attached to a flat platform used in both the microPETreg and PET/CT imaging sessions to perform landmark based co-registration of the CT and microPETreg images. An automated registration method based on mutual information was also evaluated. The co-registered CT images were segmented into bone, soft tissue, and lungs and the respective attenuation coefficients at 511 keV were used to generate a transmission image for attenuation and scatter correction. Using this approach, high resolution co-registered CT and microPETreg images were obtained without the need for a dedicated small animal CT scanner or traditional PET transmission scanning. This improves the intreptation of microPET images and the correction for attenuation and scatter may be important when scanning larger species or multiple animals simultaneously
Nuclear Science Symposium Conference Record, 2004 IEEE; 11/2004
-
[show abstract]
[hide abstract]
ABSTRACT: MicroPET-Focus-F120 is the latest model of dedicated small animal PET scanners from CTI-Concorde Microsystems LLC, (Knoxville, TN). This scanner, based on the geometry of the microPET-R4, takes advantage of several system design changes and modifications to the coincidence processing electronics that improve the image resolution, sensitivity, and counting rate performance as compared to the predecessor models. This work evaluates the performance of the Focus-F120 system and shows its improvement over the earlier models. In particular, the spatial resolution has been shown to improve from 2.20 to 1.75 mm at 0.5mm radial distance, the peak absolute sensitivity to increase from 4.1% to 7.1% in comparison to the microPET-R4. The counting rate capability, expressed in NECR, was shown to peak at over 800 kcps at 88 MBq, while the microPET-R4 peak is reached at 167 MBq, in a mouse phantom. For this small phantom, the NECR counting rate is limited by the data transmission bandwidth between the scanner and the acquisition console. Evaluation of image quality and quantitation accuracy was also performed using specially designed phantoms and animal experiments.
Nuclear Science Symposium Conference Record, 2004 IEEE; 11/2004
-
[show abstract]
[hide abstract]
ABSTRACT: This study empirically compares two approaches to parallel 3D OSEM that differ as to whether calculations are assigned to nodes by projection number or by transaxial plane number. For projection space decomposition (PSD), the forward projection is completely parallel, but backprojection requires a slow image synchronization. For image space decomposition (ISD), the communication associated with forward projection can be overlapped with calculation, and the communication associated with backprojection is more efficient. To compare these methods, an implementation of 3D OSEM for three PET scanners is developed that runs on an experimental 9-node, 18-processor cluster computer. For selected benchmarks, both methods exhibit speedups in excess of eight or nine nodes, and comparable performance for the tested range of cluster sizes.
IEEE Transactions on Nuclear Science 11/2003; · 1.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: MicroPET II is a second-generation microPET scanner dedicated to high resolution PET imaging of small animals. The system consists of 90 scintillation detector modules arranged in a 3-ring configuration with a radius of 16.0 cm and ail axial extent of 4.9 cm. Each detector module consists of a 14×14 array of lutetium oxyorthosilicate crystals coupled to a multi-channel photomultiplier tube (Hamamatsu H7546) through a coherent optical fiber bundle. Printed circuit boards with a charge-division readout scheme were used to decode the 196 crystals in each array from 64 anode signals. Electronics from Concorde Microsystems. Inc. was used for signal amplification, digitization, and coincidence processing. Preliminary data showed a system with peak sensitivity of 2.26%. Energy resolution ranges from 28% to 75% with a mean of 42%. Image resolution ranges from 1.07 mm FWHM at the center of field of view (CFOV) to 1.40 mm FWHM in the radial direction and 1.14 mm FWHM in the tangential direction at 1 cm offset from CFOV. Further improvements in image and energy resolution are expected when the system geometry is fully modeled and the crystal lookup tables are improved.
Nuclear Science Symposium Conference Record, 2002 IEEE; 12/2002
-
[show abstract]
[hide abstract]
ABSTRACT: This study empirically compares two approaches to parallel 3D OSEM that differ as to whether calculations are assigned to nodes by projection number or by transaxial plane number. For projection space decomposition (PSD), the forward projection is completely parallel, but backprojection requires a slow image synchronization. For image space decomposition (ISD), the communication associated with forward projection can be overlapped with calculation, and the communication associated with backprojection is more efficient. To compare these methods, an implementation of 3D OSEM for three PET scanners is developed that runs on an experimental, 9-node, 18-processor cluster computer. For selected benchmarks, both methods exhibit speedups in excess of 8 for 9 nodes, and comparable performance for the tested range of cluster sizes.
Nuclear Science Symposium Conference Record, 2002 IEEE; 12/2002
-
[show abstract]
[hide abstract]
ABSTRACT: Using iterative three-dimensional (3D) reconstruction techniques for reconstruction of positron emission tomography (PET) is not feasible on most single-processor machines due to the excessive computing time needed, especially so for the large sinogram sizes of our high-resolution research tomograph (HRRT). In our first approach to speed up reconstruction time we transform the 3D scan into the format of a two-dimensional (2D) scan with sinograms that can be reconstructed independently using Fourier rebinning (FORE) and a fast 2D reconstruction method. On our dedicated reconstruction cluster (seven four-processor systems, Intel PIII@700 MHz, switched fast ethernet and Myrinet, Windows NT Server), we process these 2D sinograms in parallel. We have achieved a speedup > 23 using 26 processors and also compared results for different communication methods (RPC, Syngo, Myrinet GM). The other approach is to parallelize OSEM3D (implementation of C Michel), which has produced the best results for HRRT data so far and is more suitable for an adequate treatment of the sinogram gaps that result from the detector geometry of the HRRT. We have implemented two levels of parallelization for four dedicated cluster (a shared memory fine-grain level on each node utilizing all four processors and a coarse-grain level allowing for 15 nodes) reducing the time for one core iteration from over 7 h to about 35 min.
Physics in Medicine and Biology 08/2002; 47(15):2651-8. · 2.83 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We have investigated two strategies to speedup reconstruction of data from our high resolution PET scanner (HRRT) on a dedicated cluster (7 nodes with 4 PIII Xeon@700 MHz, switched Fast Ethernet and Myrinet networking, Windows NT). With the first strategy, FORE/FOREJ and a fast 2D reconstruction method, we were able to reduce the 2D reconstruction time from 38 minutes to approx. 100 seconds. The second approach was to accelerate OSEM3D with a two-stage parallelization scheme resulting in a drop of reconstruction time from about 8 hours on one CPU to approx. 35 minutes for one core iteration.
Nuclear Science Symposium Conference Record, 2001 IEEE; 12/2001
-
D.F. Newport
[show abstract]
[hide abstract]
ABSTRACT: Since its creation in the mid 1980's, Magic has been one of the most widely used layout tools for Manhattan (Mead and Conway) style IC layout. This is due to its flexibility, ease of use, and cost (free via ftp). Magic has been ported to many platforms, including the MAC-II and DOS, but mainly Unix-based platforms. The DOS version was limited and not widely used. With the proliferation of Windows 95/NT platforms, it seems only natural that Magic be ported to Windows 95/NT. Yet, there does not appear to be a port to Windows 95/NT available. The reason for this appears to be the difficulty of programming “windows” in this environment. We believe that we have a way around this difficulty. Development is currently underway to port Magic to Windows 95/NT using Tcl and the Tk Toolkit. This should ease the interface to the window system through “generic” routines. As a matter of fact, the same Tcl/Tk display driver should function under X11 Unix-based platforms us well as Windows 95/NT and other platforms with Tcl and Tk Toolkits
Microelectronic Systems Education, 1997. MSE '97. Proceedings., 1997 IEEE International Conference on; 08/1997
-
[show abstract]
[hide abstract]
ABSTRACT: This paper presents two new rebinning algorithms for the reconstruction of three-dimensional (3-D) positron emission tomography (PET) data. A rebinning algorithm is one that first sorts the 3-D data into an ordinary two-dimensional (2-D) data set containing one sinogram for each transaxial slice to be reconstructed; the 3-D image is then recovered by applying to each slice a 2-D reconstruction method such as filtered-backprojection. This approach allows a significant speedup of 3-D reconstruction, which is particularly useful for applications involving dynamic acquisitions or whole-body imaging. The first new algorithm is obtained by discretizing an exact analytical inversion formula. The second algorithm, called the Fourier rebinning algorithm (FORE), is approximate but allows an efficient implementation based on taking 2-D Fourier transforms of the data. This second algorithm was implemented and applied to data acquired with the new generation of PET systems and also to simulated data for a scanner with an 18 degrees axial aperture. The reconstructed images were compared to those obtained with the 3-D reprojection algorithm (3DRP) which is the standard "exact" 3-D filtered-backprojection method. Results demonstrate that FORE provides a reliable alternative to 3DRP, while at the same time achieving an order of magnitude reduction in processing time.
IEEE Transactions on Medical Imaging 05/1997; 16(2):145-58. · 3.64 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: For count-limited PET imaging protocols, two different approaches
to reducing statistical noise are volume, or 3D, imaging to increase
sensitivity, and statistical reconstruction methods to reduce noise
propagation. These two approaches have largely been developed
independently, likely due to the perception of the large computational
demands of iterative 3D reconstruction methods. The authors present
results of combining the sensitivity of 3D PET imaging with the noise
reduction and reconstruction speed of 2D iterative image reconstruction
methods. This combination is made possible by using the
recently-developed Fourier rebinning technique (FORE), which accurately
and noiselessly rebins 3D PET data into a 2D data set. The resulting 2D
sinograms are then reconstructed independently by the ordered-subset EM
(OSEM) iterative reconstruction method, although any other 2D
reconstruction algorithm could be used. The authors demonstrate
significant improvements in image quality for whole-body 3D PET scans by
using the FORE+OSEM approach compared with the standard 3D Reprojection
(3DRP) algorithm. In addition, the FORE+OSEM approach involves only 2D
reconstruction and it therefore requires considerably less
reconstruction time than the 3DRP algorithm, or any fully 3D statistical
reconstruction algorithm
Nuclear Science Symposium, 1996. Conference Record., 1996 IEEE; 12/1996
-
Nuclear Science Symposium and Medical Imaging Conference, 1993., 1993 IEEE Conference Record.; 12/1993
-
[show abstract]
[hide abstract]
ABSTRACT: An application specific integrated circuit (ASIC) is designed and
fabricated. It implements many of the current functions found in the
digital front-end electronics for a high resolution positron emission
tomography scanner. The ASIC performs crystal selection, energy
qualification, time correction, and event counting functions for block
technology high resolution PET scanners. Digitized x and y position,
event energy, and time information are used by the ASIC to determine
block crystal number, qualify the event based on energy, and correct the
event time. Event counting and block dead time calculations are
performed for system dead time corrections. A loadable sequencer for
controlling the analog front-end electronics is implemented. The ASIC is
implemented in a 37000 gate, 1.0-μm CMOS gate-array and is capable of
handling four million events/second while reducing parts count, cost,
and power consumption over current board-level designs
IEEE Transactions on Nuclear Science 09/1993; · 1.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: It is pointed out that application-specific integrated circuits
(ASICs) can now be designed using high-quality, inexpensive tools and
can be fabricated in small quantities using MOSIS (metal oxide
semiconductor implementation service). Numerous computer-aided design
tools developed under government sponsorship are available to
organizations within the United States for just a media handling fee.
These tool integration and enhancement activities have resulted in a
proven set of high-quality aids that permit the design of custom and
semicustom analog and digital ASICs. Examples of projects implemented
using this tool set are given along with the support activities that are
being conducted to transfer this technology to other federal agencies
and universities
IEEE Transactions on Nuclear Science 05/1990; · 1.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A pipelined parallel architecture for processing time-coincident data is described. The data to be processed are from a ring of positron emission detectors and are used for tomography. The architecture consists of an array of identical modules to determine if opposing detectors have detected a positron event. This requires a large number of internal connections and is practical only in VLSI. By implementing this architecture in VLSI, the size and cost of existing circuitry is reduced, along with the length requirements for an expensive high-speed cable
CompEuro '89., 'VLSI and Computer Peripherals. VLSI and Microelectronic Applications in Intelligent Peripherals and their Interconnection Networks', Proceedings.; 06/1989
-
[show abstract]
[hide abstract]
ABSTRACT: A VLSI (very large scale integration) architecture for coincidence
detection and selection used in the reconstruction of positron emission
tomography images is described. Implementing this architecture in VLSI
not only reduced the size and cost of the existing circuitry but also
reduced the length requirements of an expensive high-speed cable. The
architecture requires a large number of internal connections and is
practical only in VLSI. The silicon area needed for making these
connections was minimized by using nearest-neighbor communication within
an array of modules. The design complexity of the architecture was kept
manageable by replicating a single module 56 times within the
array
IEEE Transactions on Nuclear Science 03/1989; · 1.45 Impact Factor
