Papers by Rejean Fontaine
The RatCAP conscious small animal PET tomography
14th IEEE-NPSS Real Time Conference, 2005., 2005
The RatCAP is a small, head mounted PET tomograph designed and built to image the brain of an awa... more The RatCAP is a small, head mounted PET tomograph designed and built to image the brain of an awake rat. It allows PET imaging studies to be carried out on laboratory rats without the use of anesthesia, which severely suppresses brain functions and affects many of the neurological activities that one would like to study using PET. The tomograph consists
Fast high lutetium content scintillators as candidates for APD-based phoswich detectors with depth-of-interaction (DOI)
2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC), 2009
... Nucl. Sci., vol. 56, pp. 3-9, 2009. [15] N. Viscogliosi, J. Riendeau, P. Berard, M.-A. Tetrau... more ... Nucl. Sci., vol. 56, pp. 3-9, 2009. [15] N. Viscogliosi, J. Riendeau, P. Berard, M.-A. Tetrault, R. Lefebvre, R. Lecomte and R. Fontaine, "Real time implementation of a wiener filter based crystal identification algorithm," IEEE Trans. Nucl. Sci., vol. 55, pp. 925-929, 2008. 2432 ...
Preliminary results of a data acquisition subsystem for distributed, digital, computational, APD-based, dual-modality PET/CT architecture for small animal imaging
IEEE Symposium Conference Record Nuclear Science 2004., 2004
A new highly integrated data acquisition (DAQ) system for a combined, APD-based, dual-modality PE... more A new highly integrated data acquisition (DAQ) system for a combined, APD-based, dual-modality PET/CT scanner, implementing both analog and digital electronics on the same board, has been fabricated and tested. The DAQ system was designed to achieve high-precision (<1 ns) coincidence detection in PET and high-rate event counting in CT imaging using the same detectors and electronics. One DAQ board holds 64 parallel detector channels that can be sampled directly at the output of the charge-sensitive preamplifiers (CSP) at a rate of 100 MHz with free-running analog-to-digital converters (ADC) from Maxim. Digital signal processing is performed in field programmable gate arrays (FPGAs) from Xilinx. Independent 500 V voltage regulators are mounted on board for optimum biasing of individual APDs coupled to phoswich detectors. The DAQ board has been fabricated on a 12 copper layers printed circuit board (PCB). The low-noise analog front-end is directly interfaced on board through differential CSP outputs to the high-speed digital circuits for optimum coupling and noise immunity. The board shows excellent electrical characteristics with all circuitry powered up, featuring a mean signal to noise and distortion ratio (SINAD) of 47.7 dB over all 64 channels when supplied with a 10 MHz sine waveform at its input. Initial performance characteristics with BGO/LSO phoswich detectors are reported.
Initial Performance of the RatCAP, a PET Camera for Conscious Rat Brain Imaging
IEEE Nuclear Science Symposium Conference Record, 2005, 2005
... [8] ML Purschke, SS Junnarkar, A. Kandasamy, P. O&amp;amp;amp;amp;#x27;Connor, J.-F. Prat... more ... [8] ML Purschke, SS Junnarkar, A. Kandasamy, P. O&amp;amp;amp;amp;#x27;Connor, J.-F. Pratte ... P. Vaska, D. Schlyer, M. Purschke, CL Woody, S. Stoll, S. Southekal, and A. Villanueva, &amp;amp;amp;amp;quot;Statistical 3D Image Reconstruction for the RatCAP PET Tomograph using a physically accurate, Monte Carlo based ...
Performance Enhancement of the RatCAP Awake Rat Brain PET System
2006 IEEE Nuclear Science Symposium Conference Record, 2006
The first full prototype of the RatCAP PET system, designed to image the brain of a rat while con... more The first full prototype of the RatCAP PET system, designed to image the brain of a rat while conscious, has been completed. Initial results demonstrated excellent spatial resolution, 1.8 mm FWHM with filtered backprojection and &amp;lt;1.5 mm FWHM with a Monte Carlo based MLEM method. However, noise equivalent countrate studies indicated the need for better timing to mitigate the effect
IEEE Symposium Conference Record Nuclear Science 2004., 2004
The RatCAP is a small, head mounted PET tomograph being designed and built to image the brain of ... more The RatCAP is a small, head mounted PET tomograph being designed and built to image the brain of an awake rat. It will allow PET imaging studies to be carried out on laboratory rats without the use of anesthesia, which severely suppresses brain functions and affects many of the neurological activities that one would like to study using PET. In addition, it will allow the study of animal behavior while simultaneously acquiring PET data. The tomograph consists of a 4 cm diameter ring containing 12 block detectors, each of which is comprised of a 4x8 array of 2.2x2.2x5 mm 3 LSO crystals read out with a matching APD array. The APDs are read out using a custom designed ASIC and VME readout system. Most of the detector components for the RatCAP have been received and the final detector is now under construction. This paper summarizes the status of the project and gives results on detector component testing and performance, development of the readout system, results on image reconstruction, and studies on animal behavior while wearing the ring.
2007 IEEE Nuclear Science Symposium Conference Record, 2007
The original prototype RatCAP PET scanner for conscious rat brain imaging has undergone a redesig... more The original prototype RatCAP PET scanner for conscious rat brain imaging has undergone a redesign of most major components resulting in a distinct 2 nd -generation instrument. While maintaining the same field of view (38 mm diameter, 18 mm axial) and similar overall architecture, the new design allows for longer crystals to provide approximately a factor of 2 increase in coincidence sensitivity with a minimal increase in size and weight. The front-end electronics ASIC has been significantly upgraded, featuring programmable amplifier gains, lower noise, differential digital communication (LVDS), and selectable energy window modes and analog outputs for debugging. The rigid-flex circuit interconnecting the 12 blocks is now more mechanically stable and draws less power which minimizes APD gain shifts. The downstream time-stamp and signal processing module (TSPM) has been modified to be compatible with the new ASICs and further includes DACs for threshold control, twice as many inputs, and a doubling of data throughput capacity. The user interface and data acquisition software is in Labview, and data processing and image reconstruction software is being further developed to maximize imaging accuracy for quantitative neuroscience studies. Finally, a new mechanical support system has been constructed to improve the rat's tolerance of the scanner. Preliminary data indicate improved energy and time resolution compared to the 1 st -generation prototype and first images of the rat brain while conscious have been obtained.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009
Visualization and quantification of biological processes by molecular imaging in small animals su... more Visualization and quantification of biological processes by molecular imaging in small animals such as rats and especially mice require the best possible spatial resolution in positron emission tomography (PET). A new avalanche photodiode (APD) detector module, the LabPET II, was developed to achieve submillimetre spatial resolution for this purpose. The module consists of two monolithic APD arrays of 4 Â 8 pixels, each with an active area of 1.1 Â1.1 mm 2 at a 1.2 mm pitch. The two APD arrays mounted in a custom ceramic PGA holder are coupled to an 8 Â 8 tapered LYSO scintillator array designed to accommodate one-to-one coupling between individual APDs and crystal pixels. To investigate the module performance, an analog test board with four 16-channel preamplifier ASICs was designed to be interfaced with the LabPET TM digital processing electronics. At a standard APD operating bias, a mean energy resolution of 27.572.1% was typically obtained with a relative standard deviation of 13.8% in signal amplitude for the 64 individual pixels when irradiated with 511 keV photons. With two modules in coincidence, a mean timing resolution of 5.070.2 ns FWHM was measured. Finally, an intrinsic spatial resolution of 0.82 mm FWHM was measured by sweeping a 22 Na point source between the two detector arrays. The LabPET II detector module demonstrates promising characteristics for dedicated small animal PET imaging at submillimetre resolution and, with some further optimization, would be suitable as the building block for a dual-modality combined PET/CT system.
LabPET II, a novel 64-channel APD-based PET detector module with individual pixel readout achieving submillimetric spatial resolution
… Record, 2008. NSS' …, 2008
A new avalanche photodiode (APD) detector module, the LabPET II, was developed to achieve submill... more A new avalanche photodiode (APD) detector module, the LabPET II, was developed to achieve submillimetre spatial resolution for small animal molecular imaging. The module consists of two monolithic APD arrays of 4× 8 pixels, each with an active area ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2007
ABSTRACT The development of new molecular probes targeting receptors with high specificity in sel... more ABSTRACT The development of new molecular probes targeting receptors with high specificity in selected cells and tissues highlights the importance of obtaining the anatomical context in Positron Emission Tomography (PET) imaging. This can be achieved using another imaging modality, such as X-ray Computed Tomography (CT) or Magnetic Resonance Imaging (MRI), but the anatomic and molecular images obtained sequentially with different scanners must subsequently be co-registered and are subjected to motion artifacts. Conventional CT imaging also contributes a significant dose, which may compromise the benefits of longitudinal molecular imaging studies in the same subject. To overcome these difficulties, we have investigated the use of the LabPET™ detector and electronics as a multi-modal detection system. Based on fast light emitting inorganic scintillators individually coupled to avalanche photodiodes and parallel, low-noise, fast digital processing electronics, the proposed detector front-end is suitable for coincidence detection of annihilation radiation (511 keV) in PET and for ultra-fast low-energy X-ray photon counting in CT. This combined detection system enables concurrent PET/CT imaging while potentially achieving superior image contrast sensitivity for a given dose in CT photon-counting mode. Anatomical images with millimeter spatial resolution and sufficient tissue contrast for anatomical localization in small animals have been obtained with doses in the mGy range. The CT performance for dual-modality imaging of small animals was analyzed in terms of spatial resolution, noise and image contrast sensitivity as a function of dose.
System Integration of the LabPET Small Animal PET Scanner
2006 IEEE Nuclear Science Symposium Conference Record, 2006
To address modern molecular imaging requirements, a digital positron emission tomography scanner ... more To address modern molecular imaging requirements, a digital positron emission tomography scanner for small animals has been developed at Universite de Sherbrooke. Based on individual readout of avalanche photodiodes (APD) coupled to a LYSO/LGSO phoswich array, the scanner supports up to 3072 channels in a 16.2 cm diameter, 7.5 cm axial field of view with an isotropic 1.2 mm FWHM
Real-Time Coincidence Detection System for Digital High Resolution APD-based Animal PET Scanner
IEEE Nuclear Science Symposium Conference Record, 2005, 2005
Abstract A centralized, fully digital, FPGA-based coincidence detection system has been develope... more Abstract A centralized, fully digital, FPGA-based coincidence detection system has been developed for the LabPET APD-based scanner. The digital flexibility allows excellent timing resolution using digital signal processing and high precision crystal identification. In this digital ...
An investigation of Lu<inf>1.8</inf>Gd<inf>0.2</inf>SiO<inf>5</inf>:Ce (LGSO) phoswich crystal identification by digital methods
2011 IEEE Nuclear Science Symposium Conference Record, 2011
LGSO-90%Lu scintillators are promising new candidates for future positron emission tomography (PE... more LGSO-90%Lu scintillators are promising new candidates for future positron emission tomography (PET) scanners, offering high light output (90–120% of NaI(Tl) with avalanche photodiode readout) and a range of decay times from τ = 28 ns to τ = 48 ns by varying cerium concentration during the crystal fabrication process. Such diversity of crystal properties makes it possible to create multiple phoswich detector combinations for improving spatial resolution or measuring depth-of-interaction in PET imaging. This investigation was performed to identify the allowable range of decay time differences that can be used in phoswich detector pairs while still achieving acceptable crystal identification accuracy. The various phoswich arrangements were tested using the LabPET digital electronics implemented with different pulse-shape identification algorithms, including least-mean-square (LMS) auto-regressive method and Wiener filter linear optimization method, to obtain the discrimination error rate. Each phoswich pair was tested with three different low-energy thresholds (150, 250 and 350 keV) to help underlining possible limitations. Overall, the Wiener filter yielded better results. As expected, discrimination was more accurate when using the higher energy threshold of 350 keV. Given an arbitrarily chosen maximum identification error rate of 10%, a decay time difference larger than 12 ns was required with the LMS filter and a 250 keV energy threshold. An even larger decay time difference was required if the slowest crystal decay time was greater than 45 ns. With the Wiener filter and a 250 keV threshold, a decay time difference of only 5 ns was found acceptable if the slowest crystal decay time was under 38 ns. In contrast, when the fastest crystal decay time was higher than 38 ns, a decay time difference of 10 ns or more was required. In summary, when using a Wiener filter-based identification algorithm, a relatively wide range of LGSO crystal combinations can be used to achieve accurate crystal identification in phoswich detectors for PET imaging.
A Microvolumetric β Blood Counter for Pharmacokinetic Pet Studies in Small Animals
IEEE Nuclear Science Symposium Conference Record, 2005, 2005
Radiotracer kinetic modeling in small animals with positron emission tomography (PET) requires th... more Radiotracer kinetic modeling in small animals with positron emission tomography (PET) requires the determination of the blood tracer concentration as a function of time. A continuous blood counting system was designed to measure the input function from rats and mice in real time. The system consists of a flow-through beta counter made of silicon PIN photodiodes and a mul syringe
An FPGA-Based, 12-Channel TDC And Digital Signal Processing Module For The RatCAP Scanner
IEEE Nuclear Science Symposium Conference Record, 2005, 2005
Abstract Front end digital signal processing and VME based DAQ electronics for the RatCAP (Rat Co... more Abstract Front end digital signal processing and VME based DAQ electronics for the RatCAP (Rat Conscious Animal PET) is discussed. All digital approach to front end signal processing for the mobile animal PET scanner is presented. Altera Cyclone family FPGA based ...
Comparison of coincidence identification techniques for high resolution PET
2008 IEEE Nuclear Science Symposium Conference Record, 2008
ABSTRACT For increasing the resolution and sensitivity of a PET scanner one of the possible paths... more ABSTRACT For increasing the resolution and sensitivity of a PET scanner one of the possible paths to follow consists in using low energy thresholds such that multiple events, specially triples, are present in the data. But if these events are going to be used for the image reconstruction, first, a good identification algorithm should be applied to the data. In this work we have focused in two commonly used sorting algorithms: those which use only a single time coincidence window opened at a time, SW, and those which use multiple simultaneous windows, MW. The investigated sorting methods are simple versions that use exclusively timestamps but do not take advantage of other possible information items, such as energy deposition and/or relative positions of the crystals.
A Sub-Nanosecond Edge Detection System using embedded FPGA fabrics
2009 16th IEEE-NPSS Real Time Conference, 2009
Abstract The time to digital converter (TDC) concept is quite useful to obtain crucial timing inf... more Abstract The time to digital converter (TDC) concept is quite useful to obtain crucial timing information for nuclear radiation detection such as PET imaging applications. The high resolution nature of TDC makes them sensitive to processing and to temperature ...
A data acquisition sub-system for distributed, digital, computational, APD-based, bimodal PET/CT architecture for small animal imaging
2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515), 2003
The integration of a positron emission tomography (PET) scanner and a computed tomography (CT) sc... more The integration of a positron emission tomography (PET) scanner and a computed tomography (CT) scanner using the same detection system is a real challenge. The goal of the proposed PET/CT scanner design is to achieve high-speed data acquisition with a coincidence time window smaller than 10 ns and less than 1 mm spatial resolution in both PET and CT imaging
Roadmap to fully-digital PET/CT scanners
2007 IEEE Nuclear Science Symposium Conference Record, 2007
The ever-increasing needs of molecular imaging now require significant upgrade of conventional PE... more The ever-increasing needs of molecular imaging now require significant upgrade of conventional PET and CT scanners. Upcoming research protocols ask for low doses, submillimeter resolution, high sensitivity and multimodality. Current scanner technologies are mainly based on analog ASICs having a long design-cycle which hinders rapid scanner improvements and can hardly keep up with the new requirements of biomedical research. With
LabPET II, an APD-based PET detector module with counting CT imaging capability
2011 IEEE Nuclear Science Symposium Conference Record, 2011
CT imaging is currently the standard modality to provide anatomical reference in PET molecular im... more CT imaging is currently the standard modality to provide anatomical reference in PET molecular imaging. Since both PET and CT rely on detecting radiation to generate images, it would make sense to use the same detection system for data acquisition. Merging PET and CT hardware imposes stringent requirements on detectors, including wide dynamic range with high signal-to-noise ratio for good
Uploads
Papers by Rejean Fontaine