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IEEE Symposium (IUS) Ultrasonics

作者： Hong Wan P. VanBaren E. Ebbini C. Cain Bioengineering Program University of Michigan Ann Arbor MI USA Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

The possibility of using phased array generated multiple-focus patterns to reduce the overall treatment time in ultrasound surgery while restraining prefocal heating was investigated by simulating the performance of different possible schemes, i.e., single-focus scans, multiple-focus scans, and simultaneous multiple focusing without scanning, when used to "ablate" a 10/spl times/10/spl times/10 mm/sup 3/ volume 100 mm deep. In all cases, forty-one foci were used to cover the treatment volume. Multiple-focus scans were arranged into nine groups which were scanned in a raster fashion, as with single-focus scans. Keeping the treatment time constant, the maximum intensities, maximum thermal doses, dose distributions and prefocal heating zones for the different schemes were compared. It was found that the non-scanned simultaneous multiple-focus case required the smallest maximum intensity and dose, and resulted in the most even dose distribution. Single-focus raster scanning of individual lesions, as currently used with fixed-focus transducer, gave the worst results. These results show that multiple-focus patterns help considerably in reducing the maximum intensity and dose, and in generating a more even dose distribution assuming the same treatment time and prefocal heating. Alternatively they can be used to significantly reduce treatment time while keeping the maximum intensity and prefocal heating below predetermined limits.

关键词： Phased arrays Ultrasonic imaging Surgery Heat treatment Power generation Lesions Heat engines Cooling Biomedical engineering computer science

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2D large aperture ultrasound phased arrays for hyperthermia cancer therapy: design, fabrication and experimental results

2D large aperture ultrasound phased arrays for hyperthermia ...

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IEEE Symposium (IUS) Ultrasonics

作者： P. VanBaren J.-U. Kluiwstra R. Seip Y. Zhang E.S. Ebbini C.A. Cain Electrical Engineering and Computer Science Department University of Michigan Ann Arbor MI USA Bioengineering Program University of Michigan Ann Arbor MI USA

Ultrasound has proven to be an effective modality for inducing hyperthermia for cancer therapy because of the spatial control of the SAR that may be achieved. The use of phased-array ultrasound applicators provides additional benefits because the ultrasound field may be changed rapidly (at electronic speeds) and may be used to focus the field at several locations simultaneously. To obtain these qualities, large apertures with element counts exceeding several hundred are needed. However, with the increase in the number of elements, both the control and fabrication process involve greater complexity. Therefore the construction of phased array systems, especially those using geometric focusing to increase intensity gain, has proven technically difficult. In order to avoid complex machining and mounting procedures, a modular approach to array construction has been developed. To test this approach, phased arrays with 192 and 512 elements have been designed, fabricated and characterized in the authors' laboratory. These arrays are composed of flat panels arranged to approximate a spherically shaped aperture. Experimental acoustic measurements for both arrays are presented and compared with computer simulations, showing good agreement. In addition, experimental results using these arrays, in conjunction with a control algorithm developed in the authors' lab, to induce and maintain hyperthermia in in vivo canine thigh muscle are presented. These results demonstrate the flexibility of such applicators, and the control which they can achieve over the SAR field.

关键词： Phased arrays Apertures Ultrasonic imaging Hyperthermia Cancer Applicators Medical treatment Process control Fabrication Machining

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Solution to the inverse scattering problem using a modified distorted Born iterative algorithm

Solution to the inverse scattering problem using a modified ...

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IEEE Symposium (IUS) Ultrasonics

作者： O.S. Haddadin S.D. Lucas E.S. Ebbini Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA Bioengineering Program University of Michigan Ann Arbor MI USA

Presents a new distorted Born iterative algorithm for diffraction tomography which introduces kernel distortions only at carefully selected pixel locations. This algorithm attains the performance levels achieved by existing distorted Born iterative techniques, while maintaining the robustness of the Born iterative technique, especially in noisy situations. In addition, the algorithm has lower computational complexity and faster convergence rate when compared with existing distorted Born iterative algorithms. The authors present numerical simulations of the algorithm in noisy and noise-free environments. They also discuss an elementary experimental setup which is being used to validate their tomographic imaging algorithms.

关键词： Inverse problems Iterative algorithms Working environment noise Tomography Diffraction Kernel Noise robustness Noise level Computational complexity Convergence

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Body surface Laplacian mapping of ventricular depolarization from potential recordings in humans

Body surface Laplacian mapping of ventricular depolarization...

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

作者： M. O'Hara X. Yu N. Mehdi C. Schwartz D. Wu B. Avitall B. He Bioeng. Program Illinois Univ. Chicago IL USA Department of Electrical Engineering and Computer Science University of Illinois Chicago Bioengineering Program University of Illinois Chicago Department of Medicine University of Illinois Chicago

We investigated the feasibility of obtaining body surface Laplacian maps (BSLMs) from unipolar electrocardiographic recordings in humans. The overall pattern of the BSLMs during ventricular depolarization is reproducible for subjects examined and for multiple sets of maps within a single subject. Right and left ventricular activities are well resolved in the BSLMs over the anterior chest as compared with body surface potential maps (BSPMs). Our experimental results demonstrate the feasibility of performing body surface Laplacian electrocardiographic mapping from potential recordings. The effects of measurement noise and electrode position uncertainty on the Laplacian derivation were also evaluated by computer simulation.

关键词： Laplace equations Humans Electrodes Bioelectric phenomena Electric potential computer simulation Position measurement Noise measurement Signal processing Gaussian noise

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Microemboli characterization by determination of Legendre coefficients of phase function

Microemboli characterization by determination of Legendre co...

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

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

The characterization of microemboli located in whole blood is attempted by determining the Legendre coefficients of phase function from the scattered light distribution around the medium. In the radiative transport equation, a microembolus is represented as a secondary source and assumed to have a spherical form and the first order transport approximate solution of the equation is used to describe the scattered intensity distribution. After the scattered intensities are determined at the surfaces of the medium, the orthogonal property of Legendre polynomial is used to extract the coefficients out of the intensities. From the obtained coefficients, the size and complex index of refraction of microemboli are determined.

关键词： Particle scattering Red blood cells Laboratories Cells (biology) Equations electrical capacitance tomography Polynomials Position measurement computer simulation Slabs

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A Model For The Relative Environmental Stability Of A Series Of Polyimide Capacitance Humidity Sensors

A Model For The Relative Environmental Stability Of A Series...

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International Conference on Solid State Sensors and Actuators (TRANSDUCERS)

作者： A.R.K. Ralston C.F. Klein P.E. Thomas D.D. Denton Central Research Johnson Controls Inc. Milwaukee WI USA Materials Science Program Department of Electrical and Computer Engineering and Department of Chemistry University of Wisconsin Madison Madison WI USA

A capacitance humidity sensor is used as a test de- vice to characterize the performance of thirteen polyimide films in relative humidity sensing applications. This sensor has a multilayer, free-standing film construction. It consists of a humidity sensitive polyinfide dielectric core and conductive layers consisting of carbon filled polysul- fone on each side of the polyimide film to form a capacitor. Thirteen polyimide films, including commercial polyimides and films of novel chemistry, are investigated to determine the long term stability of sensors using the films exposed to 85'C/85% RH for a total of 28 days. Differences in film chemistry are used to interpret trends in the environmental stability of the films.

关键词： Stability Polyimides Capacitance Humidity Sensor phenomena and characterization Chemical sensors Chemistry Capacitive sensors Aging Conductive films

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Synthetic phased array imaging of coronary arteries with an intraluminal array

Synthetic phased array imaging of coronary arteries with an ...

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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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