Short Courses
October 3, 2006
Abstracts and instructor information follow.
1A – Medical Ultrasound Transducers
8 am – 12 pm, Salon D
Douglas G. Wildes and L. Scott Smith
General Electric Global Research, Niskayuna, NY, USA
1B – Elasticity Imaging
8 am – 12 pm, Salon E
Stanislav Emelianov
University of Texas at Austin, Austin, TX, USA
1C – Advanced Numerical Techniques for Modeling and Simulation of SAW Devices, BAW Devices and FBARs
8 am – 12 pm, Salon F
Elireza Baghai-Wadji
RMIT University, Melbourne, Australia
2A – Medical Imaging Beamformer Design
1 pm – 5 pm, Salon D
Kai E. Thomenius
General Electric Global Research, Niskayuna, NY, USA
2B – Micromachined Ultrasonic Sensors and Actuators
1 pm – 5 pm, Salon E
Amit Lal* and B. (Pierre) T. Khuri-Yakub+
*Cornell University, Ithaca, NY +Stanford University, Stanford, CA
2C - Nonlinear Acoustics and Harmonic Imaging
1 pm – 5 pm, Salon F
Victor F. Humphrey
Institute of Sound and Vibration Research (ISVR), University of Southampton, UK
3A – Ultrasound Contrast Agents: Theory and Experimental Results
6 pm – 10 pm, Salon D
Nico de Jong* and Michel Versluis+
*Erasmus MC Rotterdam, The Netherlands, +University of Twente Enschede, The Netherlands
3B – Finite Element Modeling for Ultrasound Applications, Salon E
6 pm – 10 pm
Paul Reynolds and David Vaughn
Weidlinger Associates, Los Altos, CA, USA
3C – Flow Measurements and Doppler
6 pm – 10 pm, Salon F
Hans Torp
Norwegian University of Science and Technology, Trondheim, Norway
1A Medical Ultrasound Transducers
Douglas G. Wildes and L. Scott Smith
General Electric Global Research, Niskayuna, NY, USA
This course will provide an introduction to the design, fabrication, and testing of medical ultrasound transducers. Starting from an overview of the basic types of phased-array transducers (linear, convex, sector), we will discuss how the design for a probe is derived from its target application and how equivalent-circuit, finite-element, and acoustic field models can be used to optimize the design and accurately predict performance. A discussion of the structure of an ultrasound probe will lead to a survey of the different types of materials used in probes and their critical properties. Typical fabrication processes will be introduced and common problems in probe manufacturing will be summarized. Methods for evaluating completed transducers will be discussed. The course will highlight recent developments in probe technology, including single crystal piezoelectrics, cMUT transducers, catheters, multi-row and 2D arrays, and electronics in probes, and will discuss performance advantages and fabrication difficulties which may be associated with each.
Douglas G. Wildes is a physicist with GE Global Research. He earned an A.B. in physics and mathematics from Dartmouth College and a Ph.D. in low-temperature physics from Cornell University, then joined GE in 1985. Since 1991, Dr. Wildes' research has focused on aperture design, fabrication processes, and high-density interconnect technology for multi-row and 2D transducers for medical ultrasound. Dr. Wildes has 20 issued patents and 18 external publications. He is a member of the American Physical Society and a Senior Member of the IEEE.
L. Scott Smith is a physicist with GE Global Research. He earned B.S. and Ph.D. degrees in physics from the University of Rochester and the University of Pennsylvania respectively. Joining GE in 1976, he developed phased array probes for medical ultrasound. More recently, he examined novel probe materials and led projects on pediatric endoscopes and adaptive acoustics. Dr. Smith has 37 issued patents and over 35 refereed publications. He is a member of the American Physical Society and a Senior Member of the IEEE where he serves as Vice Chair for Transducers on the Ultrasonics Symposium's Technical Program Committee.
1B Elasticity Imaging: Signals and Systems
Stanislav Emelianov
University of Texas at Austin, Austin, TX, USA
The main objective of this course is to expose attendees to elasticity imaging with emphasis on principles, approaches and applications. The course will provide both a broad overview and comprehensive understanding of elasticity imaging, and, as such, the course is well suited for both newcomers and active researchers in the field. The course will be divided into several modules. Starting with a brief historical introduction to elasticity imaging, we will examine the foundation and basic principles of static and dynamic approaches in elasticity imaging (theory of elasticity including both the equation of equilibrium and the wave equation, mechanical properties of soft tissues, etc.). We will then discuss experimental aspects of elasticity imaging including imaging hardware, signal and image processing algorithms, etc. Speckle tracking methods will be introduced and analyzed. Techniques to map elasticity and other mechanical properties of tissue will be presented and discussed. In this part of the course, we will also analyze noise (sources) and primary artifacts, and discuss techniques to increase and optimize signal-to-noise ratio in strain and elasticity images. Finally, the ultrasound elasticity imaging techniques and their biomedical and clinical applications will be presented. Advantages and limitations of each approach will be discussed and contrasted with other elasticity imaging techniques such as MRI or optical elastography. Overall, similarities and differences between various elasticity imaging approaches will be discussed. The course will conclude with overview of several experimental and commercial systems capable of ultrasound elasticity imaging.
Stanislav Emelianov received the B.S. and M.S. degrees in physics and acoustics in 1986 and 1989, respectively, from the Moscow State University, and the Ph.D. degree in physics in 1993 from Moscow State University, and the Institute of Mathematical Problems of Biology of the Russian Academy of Sciences, Russia. In 1989, he joined the Institute of Mathematical Problems of Biology, where he was engaged in both mathematical modeling of soft tissue biomechanics and experimental studies of noninvasive visualization of tissue mechanical properties. Following his graduate work, he moved to the University of Michigan, Ann Arbor, as a post-Doctoral Fellow in the Bioengineering Program, and Electrical Engineering and Computer Science Department. From 1996 to 2002, Dr. Emelianov was a Research Scientist at the Biomedical Ultrasonics Laboratory at the University of Michigan. During his tenure at Michigan, Dr. Emelianov was involved primarily in the theoretical and practical aspects of elasticity imaging. Dr. Emelianov is currently an Assistant Professor of Biomedical Engineering at the University of Texas at Austin. His research interests are in the areas of medical imaging for therapeutics and diagnostic applications, ultrasound microscopy, elasticity imaging, photoacoustic imaging, cellular/molecular imaging, and functional imaging.
1C Advanced Numerical Techniques for Modeling and Simulation of SAW Devices, BAW Devices and FBARs
Alireza Baghai-Wadji
RMIT University, Melbourne, Australia
E-mail: alireza.baghai-wadji@rmit.edu.au
This short course focuses on modern methodologies for the acceleration and customization of analysis- and synthesis tools for microacoustic device modelling and simulation. Surface acoustic wave devices, bulk acoustic wave devices, FBARs, MEMS and RF-MEMS will be considered and higher-order effects including the radiation of electromagnetic waves in these devices will be accounted for. Following a brief review of traditional design and simulation techniques we will discuss recently developed methods which are by construction extraordinarily flexible and at the same time promise to be accurate to a desired degree. Included are the so-called conservative finite difference method, finite volume method, this author’s fast boundary element method utilizing Universal Functions, wavelet-based techniques, the multiresolution analysis, the fast multilevel multipole expansion technique, genetic algorithms, evolutionary programming, Monte Carlo method, and finally schemes for software- and hardware implementation of fast algorithms. With a particular emphasis on the design and simulation of FBARs we will explain important notions of absorbing boundaries, infinite elements, radial functions and radial wavelets. Furthermore, we will consider the concept of non-orthogonal bases- and dual bases, and address the concept of over-completeness and investigate the construction and properties of frames, dual frames and related topics. The foregoing mathematical concepts will be complemented by introducing a number of physics-based localized analysis functions. Examples will include Wannier functions, coherent states and Green’s functions induced wavelets and wavelet-like functions. More specifically, simple recipes for the construction of Meyer, Daubechies, and B-spline wavelets and their application in microacoustic device modelling and simulation will be presented. All tools necessary to conveniently follow the discussion will be developed in the classroom. A comprehensive manuscript enriched by simple and illustrative examples will be provided to course participants.
Alireza Baghai-Wadji is a Professor of Electronic and Computational Engineering at the RMIT University, School of Electrical and Computer Engineering, Melbourne, Australia. He is the Director of the Discipline Electronic and Biomedical Engineering, and School’s representative for international collaborations and curriculum development. He received his MSc, PhD, and Doctor of Science (Physical Electronics) in 1984, 1987 and 1994, respectively, from Vienna University of Technology, Vienna, Austria. In 2003 he was awarded a Doctor of Science in Quantum Electronics and Materials Science from Helsinki University of Technology, Helsinki, Finland. Prior to joining the RMIT University in March 2005 he was 1979-2005 with Vienna University of Technology: 1997-2005 an Associate Professor in the Department of Electrical and Information Technology, 1994-1997 an Assistant Professor, 1984-1994 a Research Assistant, 1979-1983 a Research Associate. He has more than 130 publications in reviewed journals and conference proceedings and is the owner of one patent in USA.
2A Medical Imaging Beamformer Design
Kai E. Thomenius
General Electric Global Research, Niskayuna, NY, USA
A goal of this course is to review the design of ultrasound front ends and beamformers from a linear systems point of view. The approach used will include transduction, beamformation, acoustic wave propagation, and image formation functions. We will discuss several analytical methods used in developing the design of a typical beamformer in use in diagnostic ultrasound today. The key points to be covered deal with methods of analysis of arrays and beamformers, the interaction of transmit and receive beams with clinically relevant targets, and how this interaction is used in image formation. A brief overview of k-space methods will be given. The means by which these analytical methods contribute to a beamformer design and the trade-offs involved are reviewed. The techniques developed for such analysis will be applied to key topics of current interest such as system miniaturization, 2D arrays and improve spatial sampling of the acoustic fields, synthetic aperture techniques, and aberration correction. Due to successes in system miniaturization such as laptop-sized systems, ultrasound is becoming a candidate modality for new clinical application. We will discuss this development and its impact on beamformer design.
Kai E. Thomenius is a Chief Technologist in the Imaging Technologies Organization at General Electric's Global Research facility in Niskayuna, NY. His focus is on Ultrasound and Biomedical Engineering. Previously, he has held senior R&D roles at ATL Ultrasound, Inc., Interspec Inc., Elscint, Inc., Inc as well as several other ultrasound companies, and is also an Adjunct Professor in the Electrical, Computer, and Systems Engineering Department at Rensselaer Polytechnic Institute where he teaches a course in general imaging. Dr. Thomenius' academic background is in electrical engineering with a minor in physiology; all of his degrees are from Rutgers University. His long-term interests have been in ultrasound beamformation and miniaturization of ultrasound scanners, propagation of acoustic waves in inhomogeneous media such as tissue, the potential of bioeffects due to those acoustic beams, and determination of additional diagnostic information from the echoes that arise from such beams. Recently he has contributed to work on coherent beamformers in millimeter wave radar applications. He is a Fellow of the American Institute of Ultrasound in Medicine.
2B Micromachined Ultrasonic Sensors and Actuators
Amit Lal* and B. (Pierre) T. Khuri-Yakub+
*Cornell University, Ithaca, NY +Stanford University, Stanford, CA
The goal of this course is to introduce the fundamentals of micromachining and the way they affect the design and performance of ultrasonic sensors and actuators. The first part of this course will cover established micromachining techniques, such as bulk micromachining and surface micromachining on silicon. The effect of fabrication conditions on material properties and dimensions, and their effects on ultrasonic device design will be presented. The following topics will be discussed with the help of case studies: (1) Electrostatic actuation of micromachined membranes: Nonlinearities and effective electromechanical coupling, (2) Comparison of bulk-PZT and thin-film piezoelectric actuation of bulk and surface micromachined structures, and silicon horn design, (3) microphones and speakers, and (4) Nonlinear ultrasound in microfluidic devices.
Amit Lal is an associate professor of electrical and computer engineering at Cornell University. He received his Ph. D. in electrical engineering from the University of California, Berkeley in 1996, and the B.S. degree from the California Institute of Technology in 1990. Amit Lal directs the SonicMEMS group at Cornell University, which focuses on ultrasonics, micromachining, modeling of piezoelectric systems, use of radioactive energy sources in microsystems, and design and analysis of integrated circuits. Specifically his group focuses on design principles for ultrasonically driven MEMS for actuation of microstructures and fluids, and radioactive power sources for autonomous MEMS. He holds several patents, relating to micromachined acoustic sources/receivers, silicon-based high-intensity ultrasonic actuators, microfluidic devices, and power sources. He is also the recipient of the NSF CAREER award for research on applications of ultrasonic pulses to MEMS. He serves on the Technical Committee on Physical Acoustics in the IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society.
B. (Pierre) T. Khuri-Yakub is a professor of electrical engineering at Stanford University. He received his Ph. D. from Stanford University in 1975, the M.S. degree from Dartmouth College in 1972, and the B.S. from the American University of Beirut, all in electrical engineering. Professor Khuri-Yakub’s group research is presently focused on the development of micro-machined ultrasonic transducers and their applications to real time volumetric ultrasound imaging, real time functional photo-acoustic medical imaging, and therapy. Other research activities involve micro-machined drop ejectors and bio-fluidic sensors and actuators. Prof. Khuri-Yakub has extensive patents and publications in the areas of thin film transducers, analog convolvers and correlators, acoustic microscopy, non-destructive evaluation, in-situ sensors, and micro-machined transducers and medical imaging.
2C Nonlinear Acoustics and Harmonic Imaging
Victor F. Humphrey
Institute of Sound and Vibration Research (ISVR), University of Southampton, UK
This course will provide an introduction to the origins of nonlinear propagation, and its consequences and applications in medical ultrasound.
The first section will review the basic physics of nonlinear propagation, and discuss the propagation of plane waves as a means of introducing nonlinear acoustics terminology. This will be followed by a discussion of the techniques used to numerically model nonlinear propagation and the specific problems of performing measurements in high amplitude fields with their associated distortion and harmonic content.
The effects of diffraction and attenuation on nonlinear propagation will then be introduced by considering the fields of transducers and arrays, and the fields they generate in tissue; this will be illustrated by a combination of experimental results and model predictions. This will lead on to a discussion of the consequences for medical ultrasound of nonlinear propagation. Finally the application to harmonic imaging will be described.
Victor Humphrey is a Professor of Acoustics at the Institute of Sound and Vibration Research (ISVR) in Southampton, U.K. He received his BSc and PhD degrees from the University of Bristol in 1975 and 1981 respectively. He then moved to the School of Physics at the University of Bath where was promoted to Senior Lecturer. In 2004 he took up his current position at ISVR. His initial research was in the area of laboratory applications of nonlinear parametric arrays in underwater acoustics. For this work he was awarded the Institute of Acoustics A.B. Wood Medal 1988. Subsequently he helped to develop a research programme on the nonlinear propagation of ultrasound in medical fields that investigated these fields both numerically and experimentally. He was awarded the University of Bath Mary Tasker Award for excellence in teaching in 1995.
3A Ultrasound Contrast Agents: Theory and Experimental Results
Nico de Jong* and Michel Versluis+
*Erasmus MC Rotterdam, The Netherlands, +University of Twente Enschede, The Netherlands
The course consists of 6 main topics:
a) First an overview will be presented of the (clinical and pre-clinical available) contrast agents, including the properties and characteristics of the gas inside the bubble and the shell surrounding it.
b) Models of the behavior of small bubbles in a ultrasound field will be discussed. Simple models based on a one dimensional mass-spring system and more complicated models including gas and shell properties.
c) Experimental ultrasound methods for UCA will be presented for characterizing the bubbles in a UCA, like harmonic and subharmonic scattering, absorption and attenuation. Also the influence of ambient pressure, temperature and gas concentration will be discussed.
d) Experimental optical methods for characterizing individual bubbles.
e) Imaging methods for contrast agents, like fundamental, harmonic, subharmonic and superharmonic and multi-pulse methods like pulse inversion, power modulation etc. and new methods like chirp excitation.
f) Ultrasound mediated drug delivery: Interaction between mammalian cells and ultrasound in the vicinity of bubbles will be discussed.
Nico de Jong graduated from Delft University of Technology, The Netherlands, in 1978. He got his M.Sc. in the field of pattern recognition. Since 1980, he has been a staff member of the Thoraxcenter of the Erasmus University Medical Center, Rotterdam, The Netherlands. At the Dept. of Biomedical Engineering, he developed linear and phased array ultrasonic probes for medical diagnosis, especially compound and transesophageal transducers. In 1986 his interest in ultrasound applications shifted toward the theoretical and practical background of ultrasound contrast agents. In 1993 he received his Ph.D. for "Acoustic properties of ultrasound contrast agents." Currently he is interested in the development of 3-D transducers and fast framing camera systems. De Jong is the project leader of STW and FOM projects on ultrasound contrast imaging and drug delivery systems. Together with Folkert ten Cate, MD, he is organizer of the annual European Symposium on Ultrasound Contrast Imaging, held in Rotterdam and attended by approximately 175 scientists from all over the world. Nico de Jong has been a part-time professor at the University of Twente since 2003.
Michel Versluis graduated in Physics in 1988 at the University of Nijmegen, the Netherlands, with a special interest in Molecular Physics and Astrophysics. Later, he specialized in the application of intense tunable UV lasers for flame diagnostics resulting in a successful defense of his PhD thesis in 1992. Michel Versluis is now a lecturer at the University of Twente, the Netherlands, in the Physics of Fluids group working on the experimental study of bubbles and jets in multiphase flows and granular flows. He also works on the use of microbubbles as a tool for medical diagnosis and therapy. Dr. Versluis teaches various courses in Fluid Mechanics, one of them focusing on the physics of bubbles.
3B Finite Element Modeling for Ultrasound Applications
Paul Reynolds and David Vaughn
Weidlinger Associates, Los Altos, CA, USA
The aim of this course is to educate the ultrasound expert in the important considerations with regards to the finite element modelling of ultrasound applications. The course will not go into details of the fundamental equations and physics of the problems, but rather the relative merits of the various approaches, leaving the audience free to consider the broader implications rather than the fine detail. By the end of the course, it is our intention that the attendees will have the basic information on finite element simulations, and several common but varied applications, with which to make informed decisions in regards to simulating their own particular problems, and therefore make best use of the resources available to them.
The four main components will be:
1) Finite Element Basics: The first section will involve an introduction to the field of finite element modelling, in order to ensure that all participants are aware of the basic assumptions inherent in the various modelling approaches.
2) Wave Propagation: The second section will concentrate on the accurate modelling of wave propagation through various media. Initial consideration will be given to the simple, linear, elastic cases and then move to include the effects of long distance propagation, material discontinuities, frequency dependant attenuation, and non-linearity (such as is prominent in higher-harmonic imaging).
3) Ultrasound and Thermal Effects: The third section will consider the use of ultrasound to heat tissue, such as with HIFU. Appropriate and accurate calculation of thermal generation (sometimes called the Bioheat Equation) and its application as a load to a thermal model will be detailed, as will advantages and disadvantages of coupling the acoustic and thermal fields, and perfusion. Difficulties in predicting effects such as cavitation and thermal variation of mechanical properties will be analysed.
4) Nonlinear electrostatic transducers (CMUTs): Capacitive Micromachined Ultrasonic Transducers (cMUTs) form a significant part of ongoing research into ultrasonic devices, and we detail the modeling requirements imposed by these highly nonlinear electrostatic devices. Full nonlinearity, contact issues, and methods of efficient modeling will be discussed in detail.
Paul Reynolds is an Associate with Weidlinger Associates Inc (WAI), developers of the PZFlex finite element modelling package. He obtained his PhD in the Finite Element Analysis of Piezocomposite Devices from the University of Strathclyde in Glasgow, Scotland, before joining WAI. Through his position as PZFlex manager, his work with both academia and industry on topics as diverse as medical imaging, medical therapeutics, SONAR, NDT, sensors and actuators has led to a broad knowledge of the modelling needs across the spectrum, and best practices to ensure efficient use of modeling resources.
David Vaughan holds the position of Principal in the Applied Science Division of Weidlinger Associates, Inc. (WAI) and is Principal-In-Charge of WAI’s Mountain View, CA office. Mr. Vaughan has an M.S. degree in Aerospace Engineering from Texas A&M University. Mr. Vaughan has extensive experience in modeling and software development for solid mechanics and multi-physics related problems, including piezoelectric applications. He directs the development of the FLEX family of computational structural dynamics codes.
3C Flow Measurements and Doppler
Hans Torp
Norwegian University of Science and Technology Trondheim, Norway
This course provides basic understanding of physical principles and signal processing methods for flow measurements and visualization; with emphasis on Doppler methods and blood flow applications. The course starts with an overview of currently used techniques for velocity estimation in pulsed and continuous wave Doppler and color flow imaging. Statistical models for the received signal, as well as commonly used velocity and flow estimators are developed. Several different simulation methods for ultrasound signals from moving blood and clutter signals will be discussed. This includes fast simulation methods, as well as full 3D point scatter models using spatial impulse response techniques or k-space analysis. Efficient simulation tools to explore estimator properties are derived, and examples on implementation in Matlab will be shown. Methods to suppress clutter signals from slowly moving targets, including regression filter will be discussed. Elements from classical estimation theory will be applied to develop minimum variance velocity estimators in the presence of clutter noise. The performance will be compared with commonly used approaches for clutter rejection and velocity estimation, and practical implementations will be discussed.
Velocity components transversal to the ultrasound beam can not be measured by Doppler techniques. However, several approaches to overcome this limitation has been proposed, including speckle tracking, transit time measurements, and lateral beam modulation. Principles and practical limitations will be discussed. Methods for visualisation of 2D vector flow information will be shown.
Hans Torp received the MS degree in mathematics in 1978, and the Dr. Techn. degree in electrical engineering in 1992; both from the University of Trondheim, Norway. Since 1980 he has been working with ultrasound technology applied to blood flow measurements and imaging at the university of Trondheim, in cooperation with GE-Vingmed Ultrasound. He is currently professor of medical technology at the Norwegian University of Science and Technology, and has since 1987 given courses on ultrasound imaging and blood flow measurements for students in electrical engineering and biophysics. His research interests includes statistical signal- and image processing with applications in medical ultrasound imaging.