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IEEE Symposium (IUS) Ultrasonics

作者： M. O'Donnell M.J. Eberle D.N. Stephens J.L. Litzza K. San Vicente B.M. Shapo Dept. of Electr. Eng. & Comput. Sci. Michigan Univ. Ann Arbor MI USA Endosonics Corporation Rancho Cordova CA USA Electrical Engineering and Computer Science Department and Bioengineering Program University of Michigan Ann Arbor MI USA

Previous synthetic array methods for intraluminal imaging of coronary arteries have been greatly extended. First, a 64 element, high efficiency, ceramic piezoelectric, array transducer operating at 20 MHz has been constructed. The array is mounted on the surface of a 1.2 mm diameter catheter appropriate for coronary artery applications. Second, integrated into the catheter tip is a custom analog chip set permitting complete data capture from the array. That is, on each firing any combination of array elements can be selected independently as transmitter or receiver. Using data acquired in this way, a complete phased array aperture (i.e. independent transmit and receive apertures) can be reconstructed. To create real-time images, a beam former based on a custom application specific integrated circuit (ASIC) has been designed and built. Beam forming coefficients were derived using an optimal filtering approach accounting for the circular geometry of the array.

关键词： Phased arrays Arteries Catheters Apertures Application specific integrated circuits Ceramics Piezoelectric transducers Transmitters Image reconstruction Filtering

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Ultrasonic displacement and strain imaging of coronary arteries with a catheter array

Ultrasonic displacement and strain imaging of coronary arter...

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IEEE Symposium (IUS) Ultrasonics

作者： B.M. Shapo J.R. Crowe A.R. Skovoroda M.J. Eberle N.A. Cohn M. O'Donnell Electrical Engineering and Computer Science Department and Bioengineerin Program University of Michigan Ann Arbor MI USA Institute of Mathematical Problems of Biology Russian Academy of Science Pushchino Russia Endosonics Corporation Rancho Cordova CA USA

Tissue elasticity can be estimated from displacement and strain images acquired under controlled deformation. We extend this approach for coronary arteries, deformed and imaged by an integrated angioplasty balloon and ultrasonic imaging probe. Because the lumen cross section of a severely occluded artery is generally not circular, we have also developed a technique to perform all motion computations in the reference frame of the lumen's geometric center. This coordinate system is independent of the imaging catheter, and consequently referencing to this frame removes artifacts associated with probe motion within the balloon during deformation. Displacements and strains estimated by phase-sensitive correlation-based speckle tracking were used to distinguish arterial plaques in simulated coronary arteries of differing elastic moduli: hard, soft, and homogenous. We have also applied these methods to images of a homogeneous gelatin phantom collected with the integrated probe. The spatial dependence of these quantities shows good agreement with theoretically predicted values.

关键词： Capacitive sensors Ultrasonic imaging Arteries Probes Elasticity Displacement control Strain control Angioplasty Catheters Phase estimation

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Gas desorption from FEA-phosphor screen pairs

Gas desorption from FEA-phosphor screen pairs

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IEEE International Conference on Vacuum Microelectronics (IVMC)

作者： M.E. Malinowski K.D. Stewart D.A.A. Ohlberg T.E. Felter A.G. Chakhovskoi C. Hunt L.E. Shea B.E. Russ J.B. Talbot J. McKittrick Sandia National Laboratories Livermore CA USA Department of Electrical and Computer Engineering University of California Davis CA USA Materials Science Program and Department of AMES University of California San Diego La Jolla CA USA

Gas desorption from a field emitter array (FEA) cathode and phosphor screen anode in a flat panel display must be controlled so that outgassing products produced during display operation do not change cathode electron emission and degrade display performance and uniformity. In order to help understand such desorption processes and to help define pumping requirements in FEA displays, we have determined the major species outgassing from two phosphor screen-FEA cathode systems. The screens were made from YAG:Cr and ZnGa/sub 2/O/sub 4/, candidate materials for use as low voltage phosphors. The YAG:Cr phosphor screen has spectral output primarily in the red, the ZnGa/sub 2/O/sub 4/, in the blue. Outgassing products were measured outside the line-of-sight of both the FEA and phosphor screens. Therefore, if the FEA-screen pairs studied were in a flat panel display, the products detected would be those pumped by appendage pumps mounted on the flat panel. In the current study, we do not measure the source of the products (FEA or screen).

关键词： Phosphors Flat panel displays Field emitter arrays Cathodes Current measurement Vacuum systems Anodes Glass Indium tin oxide Gases

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PARALLEL AND DISTRIBUTED TLM COMPUTATION WITH SIGNAL-PROCESSING FOR ELECTROMAGNETIC-FIELD MODELING

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INTERNATIONAL JOURNAL OF NUMERICAL MODELLING-ELECTRONIC NETWORKS DEVICES AND FIELDS 1995年第3-4期8卷 169-185页

作者： SO, PPM ESWARAPPA, C HOEFER, WJR NSERC/MPR Teltech Research Chair in RF Engineering Department of Electrical and Computer Engineering University of Victoria Victoria British Columbia V8W 3P6 Canada Poman So received his B.Sc. degree in computer science and physics from the University of Toronto Toronto Onatario Canada in 1985. He obtained his B.A. Sc. and M.A.Sc. degrees in electrical engineering (summa cum laude) from the University of Ottawa Ottawa Ontario Canada in 1987 and 1989 respectively. Mr So was a research engineer in the University of Ottawa from January 1989 to October 1991 his research interests included CAD techniques of microwave circuits and numerical methods for electromagnetic wave modelling. He specialized in the development of electromagnetic engineering CAD software and successfully implemented a number of electromagnetic wave simulators based on the two-dimensional and three-dimensional transmission-line matrix methods. From August 1990 to February 1991 he accompanied Professor W. J. R. Hoefer to Rome Italy and Sophia Antiopolas France. During that time he implemented a parallel version of the 3D-TLM simulator for the CM-2 Connection Machine using C-Star and X Windows Library. He is a research engineer and a Ph.D. student at the University of Victoria Victoria British Columbia Canada. He ported the 2D- and 3D-TLM simulators to DECmpp 1200 massively parallel computer using MPL C and C++. He also combined OSA90/hope a commercially available microwave CAD program with a 2D-TLM simulation module for geometry optimization using the Datapipe technique of OSA90/hope. Recently he has developed a distributed client-server computing technique for the TLM method this technique could accelerate the TLM simulation by more than an order of magnitude. Channabasappa Eswarappa received the M.Tech. degree in electrical engineering from the Indian Institute of Technology Kanpur India in 1983 and Ph. D. degree from the University of Ottawa Canada in 1990. He worked as an Assistant Executive Engineer and later as

This paper describes the implementation of transmission-line matrix (TLM) method algorithms on a massively parallel computer (DECmpp 12000), the technique of distributed computing in the UNIX environment, and the combination of TLM analysis with Prony's method as well as with autoregressive moving average (ARMA) digital signal processing for electromagnetic field modelling. By combining these advanced computation techniques, typical electromagnetic field modelling of microwave structures by TLM analysis can be accelerated by a few orders of magnitude.

关键词： Mathematical models

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Semi-automatic construction of 3D medical image-segmentation processes

Semi-automatic construction of 3D medical image-segmentation...

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Visualization in Biomedical Computing 1994

作者： Higgins, William E. Reinhardt, Joseph M. Sharp, Werner L. Departments of Electrical Engineering Computer Science and Engineering and the Bioengineering Program Pennsylvania State University University ParkPA16802 United States

We describe a GUI-based system called INTERSEG that can define 3D radiological image-segmentation processes. Using INTERSEG's GUI interface, the user first defines interactively some problem cues, which specify a segmentation task. Then, INTERSEG uses the cues to automatically construct a process for the task. The process consists of automatic image-processing operations, such as image enhancement, image segmentation, shape analysis, and measurement. With other systems, the user must resort to trial-and-error experimentation to construct such processes. © 1994 SPIE. All rights reserved.

关键词： Image enhancement

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Non-orthogonal Gabor representation of biological signals

Non-orthogonal Gabor representation of biological signals

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Proceedings of the 1994 IEEE International Conference on Acoustics, Speech and Signal Processing. Part 2 (of 6)

作者： Brown, Mark L. Williams, William J. Hero, Alfred O. Bioengineering Program University of Michigan Ann ArborMI48109 United States Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109 United States

A new technique for modelling biological signals as a linear combination of non-orthogonal Gabor logons is described. The technique has been applied to two types of signals, Event-Related Potentials (ERPs) and temporomandibular joint (TMJ) clicks. Examination of time-frequency representations of these signals revealed that they appear to consist of a small number of localized energy concentrations. Attempts to capture this apparent low dimensionality with the standard orthogonal Gabor expansion and the standard wavelet transform were unsuccessful. However, the non-orthogonal Gabor decomposition method described in this paper provides a compact, accurate signal representation and the parameters provide a good basis for ERP category and TMJ click classification. © 1994 IEEE

关键词： Wavelet transforms

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Array processing for hand-held scanners

Array processing for hand-held scanners

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IEEE Symposium (IUS) Ultrasonics

作者： M. Karaman Pai-Chi Li Pai-Chi Li M. O'Donnell Electrical Engineering and Computer Science Department and Bioengineering Program University of Michigan Ann Arbor MI USA

Multi-element synthetic aperture imaging methods suitable for applications with severe cost and size limitations are explored. Array apertures are synthesized using an active multi-element receive subaperture and a multi-element defocused transmit subaperture. The performance of multi-element methods has been tested and compared to conventional imagers through measurements with a 3.5 MHz, 128-element transducer array on different gel phantoms. The multi-element synthetic aperture methods achieve higher electronic signal to noise ratio and better contrast resolution than conventional synthetic aperture techniques, approaching conventional phased array performance

关键词： Biomedical acoustic imaging Acoustic arrays Array signal processing Biomedical signal processing Acoustic signal processing Acoustic beam focusing

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Non-orthogonal Gabor representation of biological signals

Non-orthogonal Gabor representation of biological signals

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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： M.L. Brown W.J. Williams A.O. Hero Bioengineering Program Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

A new technique for modelling biological signals as a linear combination of non-orthogonal Gabor logons is described. The technique has been applied to two types of signals, event-related potentials (ERPs) and temporomandibular joint (TMJ) clicks. Examination of time-frequency representations of these signals revealed that they appear to consist of a small number of localized energy concentrations. Attempts to capture this apparent low dimensionality with the standard orthogonal Gabor expansion and the standard wavelet transform were unsuccessful. However, the non-orthogonal Gabor decomposition method described in this paper provides a compact, accurate signal representation and the parameters provide a good basis for ERP category and TMJ click classification.< >

关键词： Enterprise resource planning Time frequency analysis Signal processing Solid modeling Biological system modeling Pattern classification Biomedical engineering Electronic mail Biology Wavelet transforms

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A laser scattering method for characterization of thromboemboli in whole blood

A laser scattering method for characterization of thromboemb...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： J. Kim J.C. Lin L.O. Reynolds Bioengineering Program Electrical Engineering and Computer Science Department Deceased University of Illinois Chicago Chicago IL USA

An optical scattering method, which measures the size, number, and type of microemboli located in flowing whole blood, is described. A perturbation solution to the one speed radiative transport equation is used to model the scattering geometry. The approximate two-parameter phase function is used to investigate scattering characteristics of microemboli. The nature of microemboli is determined by comparing the scattered intensity ratio in two forward directions, while the size and number are determined by considering intensities scattered perpendicularly to the incident direction. This method has been tested with several sizes of polystyrene spheres, air bubbles, and blood dots. The results showed excellent agreement with calculations.

关键词： Light scattering Particle scattering Detectors Red blood cells Equations Geometrical optics Laser theory Biomedical engineering Biological materials Monitoring

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Microwave Absorption in NaCl Crystals with Various Controlled Defect Conditions

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MRS Online Proceedings Library 1994年第1期347卷 467-472页

作者： Binshen Meng John Booske Reid Cooper Sam Freeman Department of Electrical and Computer Engineering University of Wisconsin Madison USA Department of Materials Science and Engineering University of Wisconsin Madison USA Materials Science Program Madison University of Wisconsin Madison USA

A thorough understanding of fundamental microwave absorption mechanisms in ionic crystalline solids is important for microwave sintering of ceramics, as well as the design of high speed electronic packaging, advanced radomes, etc. Of particular importance to these applications are how the density and type of crystalline defects affect the dominant microwave absorption mechanisms. We have designed experiments to measure microwave absorption in NaCl samples with controlled variations in defect conditions(pure, point defects, dislocations and grain boundaries) at different temperatures (20-400 °C) and frequencies (2-20 GHz). Initial results are reported and discussed.

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