Applications of Ultrasound

7 Key excerpts on "Applications of Ultrasound"

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  eBook - ePub

  Neurovascular Examination

  The Rapid Evaluation of Stroke Patients Using Ultrasound Waveform Interpretation

  • Andrei V. Alexandrov(Author)
  • 2013(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  4 Applied Principles of Ultrasound Physics

  “The only test I failed in my whole medical career was that on ultrasound physics.” Frequent comment by ultrasound technology examinees

  Introduction

  When I was at school, I dreamed of being a physicist. My physics teacher mesmerized me by explaining how Nature works. However, it was my junior school classmate and friend, Vladimir Voevodsky, a brilliant math wizard and now at the Institute for Advanced Study in Princeton, NJ, whose extraordinary abilities across the sciences made me realize early on that physics is beyond my limits. Physics remained the area to listen, learn, absorb, and try to understand how Nature works. So humbled, I decided to become a physician. This chapter provides a simplistic introduction for clinicians to a much broader and evolving knowledge about ultrasound, a small fraction of which is used in cerebrovascular imaging.

  By definition, waves are cyclic events that consist of pressure ups and downs that compress and relax the medium, supposedly leaving particles at the end of a cycle in the exact same location. Yet, when sound as a mechanical pressure wave propagates though a human body, many factors come into play and the wave eventually attenuates due to absorption and dispersion. Does the wave sent on a straight course always stay that way? Changes in direction can occur, as will be described later in this chapter. Because attenuation occurs as the wave propagates, is the energy being transformed into heat or could it interact with tissues in other potentially harmful ways? Thermal and nonthermal bioeffects are indeed of concern and regulations apply to limit emitted ultrasound power.

  For a clinician set to use ultrasound, it is important to understand the very basic principles of applied physics to explain, if need be, how a simple diagnostic ultrasound test works and why it is safe. For a scientist, examination of the human body with ultrasound offers a puzzle comparable in possibilities to a chess game or an exploration of our universe in terms of myriad of objects scattered yet interconnected across the continuum.

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  Advances In Biomedical Engineering

  • R Kenedi(Author)
  • 2013(Publication Date)
  • Academic Press

    (Publisher)

  Biomedical Applications of Ultrasound WERNER BUSCHMANN Charite Eye Hospital, Humboldt University, Berlin, Germany I. Introduction . . . . . . . . II. Modes of Action of Ultrasound on Living Cells and Tissues III. Changes in Cell and Tissue due to Ultrasound IV. Therapeutic Applications of High-intensity Ultrasound A. Tumour therapy B. Neurosurgical ultrasonic therapy . C. Ultrasonic surgery in Meniere's disease D. High-energy ultrasound in dentistry E. Ultrasound in retina surgery V. Ultrasonic Cleaning . . . . VI. Ultrasonic Diagnosis with Continuous Waves VII. Pulse Echo Techniques in Ultrasonic Diagnosis VIII. Possible Medical Applications of the Pulse Echo Method . A. Examinations of the brain . B. Ultrasonic diagnosis in cardiology. C. Ultrasonic diagnosis in other medical fields IX. Ultrasonic Diagnosis in Ophthalmology A. Ultrasonic diagnosis of the eyeball B. Ultrasonic diagnosis in the orbit . X. Injury to the Patient in Ultrasonic Diagnosis XI. Conclusion . . . . . . References. . . . . . . . I. INTRODUCTION 1 2 3 5 5 7 9 11 11 12 13 15 23 23 26 30 32 34 58 64 67 67 SCIENTIFIC activity in the medical and biological application of ultra-sonics has been concentrated in recent years on the one hand on diag-nostic methods, and on the other on therapeutic applications in which cell and tissue destruction is obtained by the use of ultrasound. For diagnosis, intensities well below the threshold of damage are mainly used. Most diagnostic methods are based on the pulse technique using pulses of a few microseconds' duration and interpulse intervals of about one millisecond. On the other hand, in order to utilise therapeutically the cell-des-tructive effects of ultrasonic waves, very high sonic intensities must be employed, moreover usually by means of focused sound beams.

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  Laser Ultrasonics Techniques and Applications

  • L.E Drain(Author)
  • 2019(Publication Date)
  • CRC Press

    (Publisher)

  Buttle and Scruby 1988). Another application might be in scaled-down measurements, e.g. of geological structures. Sub-sea exploration for oil and gas deposits depends on acoustic measurements using a broadband source (e.g. a small explosion) and hydrophone detectors. Wave propagation theory for anisotropic media is needed to interpret the results. An alternative might be to carry out model experiments in the laboratory using the pulsed laser source and a broadband ultrasonic receiver, with a suitable scale factor. There is no reason why the same approach could not be adopted to interpret the ultrasonic wave propagation in a complex structure, such as a welded node. 6.6 MEDICAL APPLICATIONS It was pointed out in Chapter 1 that medical diagnostics is one of the most important application areas for ultrasonics. Laser ultrasonic techniques have made little direct impact in this field for the reasons touched upon in that introductory chapter. The contact transducers currently in use are very adequate for the purpose, so that there is no real need for alternatives. Couplants are in any case less of a problem in medical ultrasonics, since the acoustic impedance (which controls any mismatch at the interface) of much body tissue is similar to water and other commonly used fluid couplants. Furthermore, there are rarely any contraindications to the use of an external couplant, nor are any measurements made outside normal body temperatures, which are ideal for piezoelectric materials. Finally, because the velocity of sound is a factor of four smaller in water than the compression waves in most structural metals, the spatial resolution is correspondingly better. Alternatively, comparable resolution is attainable at lower frequencies, so that it is rarely necessary to exceed 5 MHz for medical imaging. The high bandwidths of laser ultrasonic systems therefore appear to have little to offer either

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  Ultrasonic Nondestructive Evaluation

  Engineering and Biological Material Characterization

  • Tribikram Kundu(Author)
  • 2003(Publication Date)
  • CRC Press

    (Publisher)

  783 0-8493-1462-3/02/$0.00+$1.50 ' 2004 by CRC Press LLC 14 Clinical Applications of Ultrasonic Nondestructive Evaluation Yoshifumi Saijo CONTENTS 14.1 History of Medical Ultrasound ............................................................. 783 14.2 Basic Principles of Clinical Echography .............................................. 786 14.3 Examples of Clinical Images ................................................................. 791 14.4 Ultrasonic Tissue Characterization at Lower Frequencies ............... 793 14.5 Intravascular Ultrasound ....................................................................... 796 14.6 Biomedical Application of Acoustic Microscopy ............................... 798 14.6.1 Acoustic Microscopy in 100 to 200 MHz ................................ 802 14.6.2 Acoustic Microscopy in 800 to 1300 MHz .............................. 805 14.7 Summary ................................................................................................... 809 References ............................................................................................. 810 14.1 History of Medical Ultrasound Applications of Ultrasound started as underwater detection systems. Sound navigation and ranging (SONAR) systems were developed after the Titanic sank in 1912 and, during World Wars I and II, for submarine navigation. Pulsed echo ultrasound was developed as metal flaw detectors for integrity of metal hulls of large ships and tanks. The history of ultrasound was related to tragedies in those days. After World War II, the Applications of Ultrasound dramatically changed direction to avoid tragedies; it was now used in medical applications. Sub-sequent development of the instruments made it possible to use higher frequency of ultrasound with shorter pulse durations. These refinements resulted in finer resolution to detect smaller targets. The development of

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  The Mechanical Vibration: Therapeutic Effects and Applications

  • Raoul Saggini(Author)
  • 2017(Publication Date)
  • Bentham Science Publishers

    (Publisher)

  http://dx.doi.org/10.1002/352760054X ] [144] Brujan EA, Ikeda T, Matsumoto Y. Jet formation and shock wave emission during collapse of ultrasound-induced cavitation bubbles and their role in the therapeutic applications of high-intensity focused ultrasound. Phys Med Biol 2005; 50(20): 4797-809. [http://dx.doi.org/10.1088/0031-9155/50/20/004 ] [PMID: 16204873 ] [145] Feril LB, Jr, Kondo T. Major factors involved in the inhibition of ultrasound-induced free radical production and cell killing by pre-sonication incubation or by high cell density. Ultrason Sonochem 2005; 12(5): 353-7. [http://dx.doi.org/10.1016/j.ultsonch.2004.05.004 ] [PMID: 15590309 ] [146] Krasovitski B, Frenkel V, Shoham S, Kimmel E. Intramembrane cavitation as a unifying mechanism for ultrasound-induced bioeffects. Proc Natl Acad Sci USA 2011; 108(8): 3258-63. [http://dx.doi.org/10.1073/pnas.1015771108 ] [PMID: 21300891 ] [147] Buldakov MA, Hassan MA, Zhao QL, et al. Influence of changing pulse repetition frequency on chemical and biological effects induced by low-intensity ultrasound in vitro. Ultrason Sonochem 2009; 16(3): 392-7. [http://dx.doi.org/10.1016/j.ultsonch.2008.10.006 ] [PMID: 19022698 ] [148] Forrest G, Rosen K. Ultrasound: effectiveness of treatments given under water. Arch Phys Med Rehabil 1989; 70(1): 28-9. [PMID: 2916914 ] [149] Brown SA, Greenbaum L, Shtukmaster S, Zadok Y, Ben-Ezra S, Kushkuley L. Characterization of nonthermal focused ultrasound for noninvasive selective fat cell disruption (lysis): technical and preclinical assessment. Plast Reconstr Surg 2009; 124(1): 92-101. [http://dx.doi.org/10.1097/PRS.0b013e31819c59c7 ] [PMID: 19346998 ] [150] Bélanger AY. Bélanger AY. Ultrasound. In: Bélanger AY, eds. Evidence-Based Guide to Therapeutic Physical Agents. Philadelphia: Lippincott Williams & Wilkins 2003. [151] Ahmadi F, McLoughlin IV, Chauhan S, ter-Haar G. Bio-effects and safety of low-intensity, low-frequency ultrasonic exposure. Prog Biophys Mol Biol 2012; 108(3): 119-38. [http://dx.doi.org/10.1016/j.pbiomolbio.2012.01.004

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  Non-Destructive Testing

  And Testability of Materials and Structures

  • Gilles Corneloup, Cécile Gueudré, Marie-Aude Ploix(Authors)
  • 2021(Publication Date)
  • PPUR

    (Publisher)

  CHAPTER 7 ULTRASONIC TESTING Ultrasonic waves are mechanical waves that propagate through all materials (solid, liquid, and gaseous). The frequencies are higher than those of sounds and range from 1 to 10 MHz in industrial inspections. These waves are often generated by a piezoe- lectric transducer that turns an electric impulsion into vibrations. By liquid coupling the transducer to the part, in ideal conditions, ultrasonic waves propagate in a straight line at constant velocity (or celerity), until they meet an interface between two media. The energy is partially reflected and transmitted by this macroscopic interface (surface of the part, crack, inclusion, porosity, etc.) or microscopic interface (microstructure, grain boundary, etc.). The receiving transducer (which can be the emitter or another one), allows, via a device, echoes that are characteristic of ultrasonic propagation to be visualized. Measuring the reflected and transmitted amplitudes, according to the reflecting surface of the reflector (therefore its size) and the time of flight make it possible to determine the distance from the reflector. Ultrasonic testing has major benefits such as ease of implementation, non- necessary accessibility to the two sides of the part, good adaptation to the natural orientations of most defects, the possibility of passing through great thicknesses, a direct link to the mechanical characteristics of the material, and ease of information digitization. Disadvantages essentially come from the difficulty in transmitting the wave from the transducer to the part, which imposes the use of coupling (usually liquid), electro- magnetic transducers, or lasers. The very high sensitivity of propagation to the rates Fig. 7.1 Principle of ultrasound testing and representation of echoes 124 Non-Destructive Testing of heterogeneity or anisotropy of the material or to the environment (temperature, state of stress, etc.), is also an inconvenience in industrial inspections.

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  Fundamental Physics of Radiology

  • W. J. Meredith, J. B. Massey(Authors)
  • 2013(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  An intense beam of ultrasonic radiation (say of an intensity of 10 watts per cm.2 and frequency of 3 MHz) incident upon the body tissues can change and even destroy them owing to heating, cavitation, or other effects. In the past this has been used successfully in what may be termed ultrasonic diathermy, in which the radiation is focused on to the part to be destroyed. Meniere’s disease, a defect of the middle-ear mechanism which results in giddiness and loss of balance, as well as some brain conditions have been treated in this way, though the fact that a ‘window’ has to be cut through skull bone (because of the greater absorption in and reflection from bone) reduces the attraction of the method.

  Ultrasonic radiation of about 0-5 MHz and of intensities of less than about 3 watts per cm.2 is used in physiotherapy. The function here is almost certainly restricted to ‘internal’ heating of the tissues and has comforting, beneficial effects.

  Diagnostic

  By far the most important clinical applications of ultrasonic radiations are in the diagnostic field, and these will be considered under two headings. First are the methods using the fact of reflection at tissue interfaces, and second is the method using the fact that waves reflected from a moving reflector are higher or lower in frequency than the incident beam depending upon which way the reflector is moving. The first may be termed ‘echo-sounding’ or ‘sonar’ techniques—’sonar’ with sound waves being comparable with ‘radar’ with radio waves—whilst the second is usually called the Doppler method after the man who first explained the general phenomenon.

  Pulse-echo Systems

  General

  These systems are used to determine the depth of an object or a structure in the body by measuring the time taken for ultrasonic radiation reflected by it to return to the detector. The general underlying ideas can be illustrated by taking the specific example of the estimation of the depth below the skin of a piece of bone.

  A short burst (or pulse) of ultrasound, lasting a few microseconds, is directed towards the bone from a transducer in close contact with the skin, as shown in

  Fig. 282 A

  . Immediately the pulse has been emitted the transducer is switched to a detecting circuit to be able to register any radiation reflected by the body. When such radiation reaches the transducer it produces a brief piezo-electric voltage pulse which is amplified and usually displayed by the associated electronic circuits. The time between the emission of the initial pulse and the arrival of the echo depends on the depth of the bone and is a measure of that depth. Ultrasonic radiations travel at about 1500 m. per second in muscle tissue, so that if the bone is 1.5 cm. (or 1.5 × 10−2 m.) deep, the reflected ultrasound will arrive back 2(1·5 × 10−2 /1·5 × 103 sec. or 20μsec. after the emission of the transmitted pulse. The initial figure 2

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