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A new positioning algorithm for position-sensitive avalanche photodiodes

IEEE TRANSACTIONS ON NUCLEAR SCIENCE 2007年第3期54卷 433-437页

作者： Zhang, Jin Olcott, Peter D. Levin, Craig S. PerkinElmer Optoelect Santa Clara CA 95054 USA Stanford Univ Dept Radiol Stanford CA 94305 USA Stanford Univ Mol Imaging Program Stanford CA 94305 USA

We are using a novel position sensitive avalanche photodiode (PSAPD) for the construction of a high resolution positron emission tomography (PET) camera. Up to now most researchers working with PSAPDs have been using an Anger-like positioning algorithm involving the four corner readout signals of the PSAPD. This algorithm yields a significant non-linear spatial "pin-cushion" distortion in raw crystal positioning histograms. In this paper, we report an improved positioning algorithm, which combines two diagonal corner signals of the PSAPD followed by a 45 degrees rotation to determine the-X or Y position of the interaction. We present flood positioning histogram data generated with the old and new positioning algorithms using a 3 x 4 array of 2 x 2 x 3 mm' and a 3 x 8 array of 1 x 1 x 3 mm(3) of LSO crystals coupled to 8 x 8 mm' PSAPDs. This new algorithm significantly reduces the pin-cushion distortion in raw flood histogram image.

关键词： avalanche photodiode positioning algorithm positron emission tomography

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Variable Preprocessing Applied to Neural Network Position Estimators for 2-D PET

Variable Preprocessing Applied to Neural Network Position Es...

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IEEE Nuclear Science Symposium/Medical Imaging Conference (NSS/MIC)/18th International Workshop on Room-Temperature Semiconductor X-Ray and Gamma-Ray Detectors

作者： Mateo, Fernando Lerche, Christoph W. Martinez, Jorge D. Gadea, Rafael CERN European Org Nucl Res Dept Technol CH-1211 Geneva Switzerland Philips Technol GmbH Sector Med Imaging Syst Dept X Ray Imaging Syst Aachen Germany Univ Politecn Valencia Inst Inst Para Imagen Molecular I3M Valencia Spain

ISBN: (纸本)9781467301206

The goal of this paper is to study the performance of a series of variable preprocessing methods (namely: selection, scaling and projection) in combination with artificial neural networks (ANNs) to estimate the 2-D position of photon impacts on the surface of a dual head PET detector based on continuous scintillators coupled to multi-anode photomultipliers (MA-PMT). We have used a dynamic readout structure based on weighted sums to code the 64 input signals of the photodetectors into the first 8 moments of the input distribution. The preprocessing methods have been applied to these 8 moments by means of a global optimization guided by a genetic algorithm (GA) that aims to minimize a nonparametric noise estimator called Delta Test (DT). The mean systematic error and mean spatial resolution have been evaluated in all cases. The results show that the lowest systematic error is obtained by the combination of scaling and projection, while the best spatial resolution was achieved with scaling alone.

关键词： Variable preprocessing positioning algorithm Positron Emission Tomography genetic algorithm Delta Test

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Novel positioning method using Gaussian mixture model for a monolithic scintillator-based detector in positron emission tomography

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OPTICAL ENGINEERING 2011年第9期50卷 093606-093606页

作者： Bae, Seungbin Lee, Kisung Seo, Changwoo Kim, Jungmin Joo, Sung-Kwan Joung, Jinhun Korea Univ Dept Radiol Sci Seoul 136703 South Korea Korea Electrotechnol Res Inst Ansan 426170 Geonggi Do South Korea Korea Univ Sch Elect Engn Seoul 136701 South Korea Nucare Med Syst Inc Seoul 136703 South Korea

We developed a high precision position decoding method for a positron emission tomography (PET) detector that consists of a thick slab scintillator coupled with a multichannel photomultiplier tube (PMT). The DETECT2000 simulation package was used to validate light response characteristics for a 48.8 mmx48.8 mmx10 mm slab of lutetium oxyorthosilicate coupled to a 64 channel PMT. The data are then combined to produce light collection histograms. We employed a Gaussian mixture model (GMM) to parameterize the composite light response with multiple Gaussian mixtures. In the training step, light photons acquired by N PMT channels was used as an N-dimensional feature vector and were fed into a GMM training model to generate optimal parameters for M mixtures. In the positioning step, we decoded the spatial locations of incident photons by evaluating a sample feature vector with respect to the trained mixture parameters. The average spatial resolutions after positioning with four mixtures were 1.1 mm full width at half maximum (FWHM) at the corner and 1.0 mm FWHM at the center section. This indicates that the proposed algorithm achieved high performance in both spatial resolution and positioning bias, especially at the corner section of the detector. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3626579]

关键词： positioning algorithm Gaussian mixture continuous crystal flat panel photomultiplier tube positron emission tomography

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A novel positioning algorithm in wireless sensor networks based on indoor connective information

A novel positioning algorithm in wireless sensor networks ba...

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2nd IEEE Sensors Applications Symposium

作者： Shi, Wemning Huang, Chuanhe Shao, Mingkai Song, Dandan Cheng, Yong Long, Ying Wuhan Univ Sch Comp Sci Wuhan 430072 Peoples R China China Univ Geosci Sch Comp Sci Wuhan 430074 Peoples R China

ISBN: (纸本)9781424406777

Localization information of individual nodes is crucial for many advanced functions including routing, querying it? wireless sensor networks. Most of the existing localization algorithms in wireless sensor networks are designed for outdoor environment and few of them can get a reasonable localization precision in indoor environment. This paper presents a novel indoor localization scheme which uses the spatial connective information to filter distorted messages, so as to improve the positioning precision. We establish an indoor positioning dome system, make performance comparison with other schemes and fully prove the advantages of our proposed indoor scheme.

关键词： positioning algorithm wireless sensor networks indoor environment connective information

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A new iterative algorithm for pixilated and continuous scintillating crystal

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NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2011年第sup1期648卷 S79-S84页

作者： Fabbri, A. Bennati, P. Cencelli, V. Orsolini Cinti, M. N. Pellegrini, R. Petulla, F. Pani, R. de Notaristefani, F. Univ Rome Roma Tre Dept Phys Rome Italy Univ Rome Roma Tre Dept Elect Engn Rome Italy Univ Roma La Sapienza Dept Mol Med Rome Italy

In this work, we present a mean square estimation (MSE) based algorithm to calculate the position of a scintillation event within the crystal of a gamma camera dedicated to single photon imaging applications. The performances analysis takes into account pixilated and continuous shape configuration crystals, coupled to an Hamamatsu H8500C multi-anodes PMT (MA-PMT). The readout electronics used for readout has 64-independent channels each reading simultaneously the 64 anodes of the MA-PMT. An array of Nal(TI) scintillation crystal with 2.0 mm pitch, one of CsI(TI) with 1.6 mm pitch and one of YAP with 2.0 mm pixel size are taken into account. In addition, a continuous LaBr3(Ce) crystal coupled to an Hamamatsu H8500C-Mod8 MA-PMT equipped with a super-bialkali photocathode (38% QE at 380 nm) was analyzed. Position linearity and spatial resolution analyzed with collimated (for continuous crystal) and uncollimated (for pixilated crystal) Co-57 radioactive source and the scintillation points are calculated both with MSE and with a standard center of gravity (COG) algorithm. The MSE algorithm improves spatial resolution and expands the useful field of view (UFOV) of the gamma camera that nearly reaches the size of the photocathode area thus showing a great advantage with respect to the CoG algorithm. (c) 2010 Elsevier B.V. All rights reserved.

关键词： LaBr3 scintillation crystal Independent channels readout positioning algorithm

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Position correction with depth of interaction information for a small animal PET system

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NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2011年第sup1期648卷 S176-S180页

作者： Carles, M. Lerche, Ch. W. Sanchez, F. Mora, F. Benlloch, J. M. Inst Fis Corpuscular CSIC UV Valencia 46071 Spain Univ Politecn Valencia I3M Valencia 46020 Spain

In this work we study the effects on the spatial resolution when depth of interaction (001) information is included in the parameterization of the line of response (LOR) for a small animal positron emission tomography (PET) system. One of the most important degrading factors for PET is the parallax error introduced in systems that do not provide DOI information of the recorded gamma-rays. Our group has designed a simple and inexpensive method for DOI determination in continuous scintillation crystals. This method is based, on one hand, in the correlation between the scintillation light distribution width in monolithic crystals and the DOI, and, on the other hand, on a small modification of the widely applied charge dividing circuits (CDR). In this work we present a new system calibration that includes the DOI information, and also the development of the correction equations that relates the LOR without and with DOI information. We report the results obtained for different measurements along the transaxial field of view (FOV) and the image quality enhancement achieved specially at the edge of the FOV. (C) 2010 Elsevier B.V. All rights reserved.

关键词： DOI PET positioning algorithm Gamma ray imaging Continuous scintillators

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Time walk correction for TOF-PET detectors based on a monolithic scintillation crystal coupled to a photosensor array

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NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2010年第1-3期621卷 595-604页

作者： Vinke, R. Lohner, H. Schaart, D. R. van Dam, H. T. Seifert, S. Beekman, F. J. Dendooven, P. Univ Groningen Kernfys Versneller Inst NL-9747 AA Groningen Netherlands Delft Univ Technol NL-2628 JB Delft Netherlands Univ Med Ctr Utrecht NL-3584 CX Utrecht Netherlands

When optimizing the timing performance of a time-of-flight positron emission tomography (TOF-PET) detector based on a monolithic scintillation crystal coupled to a photosensor array, time walk as a function of annihilation photon interaction location inside the crystal needs to be considered. In order to determine the 3D spatial coordinates of the annihilation photon interaction location, a maximum likelihood estimation algorithm was developed, based on a detector characterization by a scan of a 511 key photon beam across the front and one of the side surfaces of the crystal. The time walk effect was investigated using a 20 mm x 20 mm x 12 mm LYSO crystal coupled to a fast 4 x 4 multi-anode photomultiplier tube (MAPMT). In the plane parallel to the photosensor array, a spatial resolution of 2.4 mm FWHM is obtained. In the direction perpendicular to the MAPMT (depth-of-interaction, DOI), the resolution ranges from 2.3 mm FWHM near the MAPMT to 4 mm FWHM at a distance of 10 mm. These resolutions are uncorrected for the similar to 1 mm beam diameter. A coincidence timing resolution of 358 ps FWHM is obtained in coincidence with a BaF(2) detector. A time walk depending on the 3D annihilation photon interaction location is observed. Throughout the crystal, the time walk spans a range of 100 ps. Calibration of the time walk vs. interaction location allows an event-by-event correction of the time walk. (C) 2010 Elsevier B.V. All rights reserved.

关键词： Positron emission tomography Timing resolution TOF-PET positioning algorithm

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A Low-Power Scheme for Localization in Wireless Sensor Networks

A Low-Power Scheme for Localization in Wireless Sensor Netwo...

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16th EUNICE/IFIP WG 6 6 Workshop (EUNICE 2010)

作者： Robles, Jorge Juan Tromer, Sebastian Quiroga, Monica Lehnert, Ralf Tech Univ Dresden D-01069 Dresden Germany

ISBN: (纸本)9783642139703

One of the most challenging issues in the design of system for Wireless Sensor Networks (WSN) is to keep the energy consumption of the sensor nodes as low as possible. Many localization systems require that the nodes keep the transceiver active during a long time consuming energy. In this work we propose a scheme to reduce the energy consumption of the mobile nodes that need to know their positions. Our strategy consists of decreasing the idle listening and an optimized allocation of the localization tasks on the nodes. Thus, the nodes that are externally powered calculate the position for the resource-constrained nodes. The scheme is based on a low-power IEEE 802.15.4 non-beacon enabled network.

关键词： localization scheme positioning algorithm idle listening wireless sensor networks

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Indoor Location Services and Context-sensitive Applications in Wireless Networks

Indoor Location Services and Context-sensitive Applications ...

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International Conference on Indoor positioning and Indoor Navigation (IPIN)

作者： Schulcz, Robert Varga, Gabor Toth, Laszlo Budapest Univ Technol & Econ Mobile Innovat Ctr Budapest Hungary

ISBN: (纸本)9781424458646

The present research was conducted at the Budapest University of Technology in the field of indoor location using radio waves of Wi-Fi networks with a focus on practical application issues. Our goal was to enhance and combine existing algorithms and create an implementation that is efficient enough to enable real-time operation in 3D space in multi-level office environments while retaining the accuracy of more complex systems and allowing the addition of valuable context-sensitive features. The proposed solution is based on proven empirical propagation models, with the ability to augment and refine with surveyed radio fingerprint data. The results of the location algorithm are combined with heuristic probability distributions layered over the floor plan, thus incorporating available sensor data (accelerometers and magnetometers found in modern devices) and floor plans. The positioning system is used by an indoor navigation software developed for smartphones and complemented by a database of annotated entities (persons, devices, areas and points of interest) to allow the inference of location-dependent, context-sensitive information through an API provided for upper layer applications. This paper primarily focuses on the practical experience accumulated during the development of the positioning algorithm, as well as the possibilities opened by having a dynamic view of all the attributes assigned to persons either directly or indirectly via their locations or other external data sources. The implementation heavily relies on the Spatial extension of the Oracle Database system, which provides geometric data types and operations. The benefits of the employment of such a system are going to be presented in the current article.

关键词： 3D space Oracle Database system Wi-Fi networks context sensitive application indoor location service indoor navigation software indoor radio mobile computing mobile radio multilevel office environment positioning algorithm smartphones spatial extension wireless LAN wireless networks

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Efficient readout electronics for multianode photomultiplier

Efficient readout electronics for multianode photomultiplier

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Conference on Hard X-Ray, Gamma-Ray and Neutron Detector Physics XII

作者： Lerche, Christoph W. Herrero-Bosch, Vicente Ferrando-Jodar, Nestor Gadea-Girones, Rafa Sanchez-Martinez, Filomeno Mora-Masa, Francisco J. Univ Politecn Valencia Inst Instrumentacin Imagen Mol E-46071 Valencia Spain Inst Fs Corpuscular Valencia Spain

ISBN: (纸本)9780819483010

We present a novel active and analog readout and preprocessing topology for position sensitive photodetectors (PSPD) that allows to readout a large variety of PSPD devices with different pixel numbers. Additionally, the topology was designed to allow for a significant reduction of analog-to-digital conversion channels. The circuit topology replaces the common passive charge divider and consists of N input stages, N x M weighting stages and M analog adder stages, where N is the number of the input channels, i.e. the number of photodetector pixels and M is the number of outputs. The circuit performs the multiplication of a matrix (the weights) with a vector (signals). For this, the input stage makes M copies of each of the N input signals, the weighting stage multiplies these signal copies with N x M different weights and the output stage adds all weighted copies with the same copy index. For high flexibility, the weights are programmable and the topology allows to interconnect several identical circuits for larger N. Measurements with a first prototype ASIC show that the achieved energy and centroid resolutions equal the resolutions from detectors with passive charge division circuits. However, the presented topology presents important advantages such as scalability. As a first application, we used the prototype ASIC to correct the sensitivity inhomogeneity of position sensitive photomultiplier tubes. As a second application for the circuit, we present a Neural Network based positioning scheme for gamma-ray imaging detectors with thick, monolithic scintillation crystals. This allows to correct the strong border artifacts of the center of gravity positioning scheme in monolithic scintillation crystals and thus enhances the spatial resolution of the gamma-ray imaging detector.

关键词： positioning algorithm Gamma-Ray Imaging Neural Network positioning

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