ISBI 2006: IEEE 2006 International Symposium on Biomedical Imaging, April 6-9, 2006, Crystal Gateway Marriott, Arlington, Virginia, U.S.A.

Recent Advances in Medical Ultrasound: Elasticity Imaging and Therapeutics

Abstract

Despite the fact that medical ultrasound is a relatively older field compared to MRI and PET, ongoing advances have allowed to continuously expand as a field in its numerous applications. In the past decade, with the advent of faster processing, specialized contrast agents, understanding of nonlinear wave propagation, novel and real-time signal and image processing and complex ultrasound transducer manufacturing, ultrasound imaging and ultrasound therapy have enjoyed a multitude of new features and clinical applications. The first part of this tutorial will give a short background on the ultrasound physics, ultrasound imaging and image formation, and will end with a short overview of recent breakthroughs and future advances. In its second part, two main recently developed areas will be described: elasticity imaging and ultrasound therapy. The first area employs state-of-the-art signal and image processing techniques in order to estimate the motion and deformation resulting from external or internal mechanical excitation of tissues. The aim is to detect and image tissues that are abnormally softer or harder than the surrounding tissues, such as tumors or infarcted myocardium, and the clinical use of these techniques will be discussed. The second area of ultrasound therapeutics will concentrate on the use of highly focused ultrasound beams using specialized transducer geometry for localized temperature increase deep in tissues and for subsequent heating or ablation of pathological tissue seated deep inside normal tissues. Monitoring techniques using ultrasound-based, elasticity-based and MRI-based techniques will be discussed as well as the current clinical applications.

  1. Part 1: The basics of medical ultrasound
    1. History of diagnostic ultrasound: early attempts to use ultrasound in diagnosis, early equipment configurations.
      • Overview of clinical applications of diagnostic ultrasound
      • Breakthrough and future development of diagnostic ultrasound
    2. Ultrasound physics
      • Wave variables: particle displacement, acoustic pressure, intensity and energy density function
      • Factors determining the sound speed
      • Reflection, refraction and transmission
    3. Fundamentals of transducers
      • Piezoelectric effect, continuous wave excitation, pulsed excitation and axial resolution.
      • Half wave resonance, matching and backing layers
      • Beam patterns and lateral resolution of non-focused and focused transducers
      • Phased array transducers; 1.5D and 2D transducers
    4. Ultrasound imaging
      • A-mode, B-mode and M-mode imaging
      • Image display: scan conversion, interpolation algorithms
      • Acoustic output of ultrasound imaging system and biological effect of ultrasound
      • Doppler effect: Doppler equation, Doppler angle, and Doppler frequency calculation
      • Continuous wave Doppler: CWD transducer, wall filter, clinical applications
      • Pulsed Doppler: spectral analysis, quadrature detection for directional Doppler, aliasing, PRF vs. maximum velocity and depth
      • Methods of deriving color flow imaging; Color Doppler and power Doppler
    5. Breakthroughs and future development of diagnostic ultrasound
      • Contrast agents
      • Elastography
      • High frequency / molecular imaging
  2. Part 2: Recent advances in elasticity imaging and ultrasound therapy
    1. Elasticity imaging
      • Mechanical properties of normal and pathological tissues
      • Techniques for mechanical excitation of tissues
      • Signal and image processing techniques used on ultrasound data to measure mechanical responses
      • Comparison with MR and optical Elastography techniques
      • Overview of available clinical systems for current and future applications of elasticity imaging techniques
    2. Ultrasound therapy
      • Fundamentals of ultrasound therapeutics: interaction of tissue with high intensity focused beams; geometry of focused ultrasound transducers; acoustic parameters change with temperature.
      • Imaging techniques for monitoring ultrasound hyperthermia and ablation: Ultrasound and MRI
      • Reflection, refraction and transmission
      • Overview of available clinical systems for current and future applications of ultrasound therapy

Material

  • Copy of slides and reprints
  • [1] E.E. Konofagou, Ultrasonic Imaging, Handbook of Biomedical Technology and Devices, Editors: James E. Moore and George Zouridakis, CRC press, 9-1 – 9-30, 2004.
  • [2] E.E. Konofagou, Quo vadis Elasticity Imaging?, Ultrasonics 42, 331-336, 2004.

About the speaker

Elisa Konofagou received her B.Sc. degree in Chemical Physics from Université de Pierre et Marie Curie, Paris VI in Paris, France and her M.Sc. degree in Biomedical Engineering from Imperial College of Physics, Engineering and Medicine in London, U.K., in 1992 and 1993, respectively. In 1999, Dr. Konofagou received her Ph.D. from the University of Houston in Biomedical Engineering for her work on elastography at the University of Texas Medical School in Houston, TX and then pursued her postdoctoral work in elasticity-based monitoring of focused ultrasound therapy at Brigham and Women’s Hospital, Harvard Medical School, Boston, MA. Professor Konofagou is currently an Assistant Professor of Biomedical Engineering and Director of the Ultrasound and Elasticity Imaging Laboratory at Columbia University, New York, USA. She is also a member of the IEEE Ultrasonics, Ferroelectrics and Frequency Control, the Acoustical Society of America and the American Institute of Ultrasound in Medicine. Her main interests are in the development of novel elasticity imaging techniques and therapeutic ultrasound methods, such as breast elastography, ligament elastography, myocardial elastography, harmonic motion imaging and focused ultrasound therapy with clinical collaborations in the Columbia Presbyterian Medical Center. She is the author of over 60 published papers in the aforementioned fields. Dr. Konofagou is a technical committee member of the Acoustical Society of America and a technical standards committee member of the American Institute of Ultrasound in Medicine. She has also been a special issue editor for the journal of Ultrasonics and is recipient of several awards including from the American Heart Association, the Acoustical Society of America and the Radiological Society of North America.


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