ultrasound 1

Ultrasound 1 - BE101 Foundations of Biomedical Imaging Fall 2009 David Hall Ph.D Department of Bioengineering University of CaliforniaSan Diego

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UCSD BE101 Fa06 Lecture 10 Slide 1 BE101 Foundations of Biomedical Imaging Fall 2009 David Hall, Ph.D. Department of Bioengineering University of California–San Diego Ultrasound I
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UCSD BE101 Fa06 Lecture 10 Slide 2 Physics of Acoustic Waves Suetens’s: Chapter 7 (pages 145-157) Today’s Outline
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UCSD BE101 Fa06 Lecture 10 Slide 3 Clinical Practice for 50 years: Non-invasive, inexpensive, portable, high temporal resolution. Also used for non-medical applications: Non-destructive testing of materials (e.g. airplane wings) Sound Navigation And Ranging (SONAR) (e.g. locate fish, submarines, study seabed) Basic Principle is SIMPLE ! Propagating wave reflects at interface between different tissues. If reflections measured as f(t) and velocity of wave in medium is known, then can obtain positional information of the tissue. Besides reflection, other phenomena can be employed: Diffraction, Refraction, Attenuation, Dispersion, and Scattering Ultrasound: Background and History
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UCSD BE101 Fa06 Lecture 10 Slide 4 Ultrasound Imaging not just used for anatomical imaging, but also functional imaging by means of blood and myocardial velocities. Principle of velocity imaging based on the “Doppler Principle”. Thus referred to as “Doppler Imaging”. (Doppler Principle: A passing ambulance or police car) “The Theory of Sound” (Lord Rayleigh 1877) and the “Piezoelectric Effect” (Pierre Curie 1880) were essential. Ultrasound first practically used in World War 1 to find submarines. Followed by non-destructive testing of metals. Ultrasound first used medically to locate brain tumors (1942). Pulse-echo system (1949) and 2D images during the 1950s. Doppler Techniques (1956) Real-time 2D image (1965) by a Siemens scanner. Electronic beam steering using phased-array (1968). Many scanners available in the mid-1970s Image quality improved through the 1980s and 1990s. Ultrasound: Background and History
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UCSD BE101 Fa06 Lecture 10 Slide 5 “Transverse Waves”- Displacement of medium particles is perpendicular to wave direction. “Longitudinal Waves”- Displacement of medium particles is parallel to wave direction. Longitudinal and Transverse Wave Motion Physics of Acoustic Waves
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UCSD BE101 Fa06 Lecture 10 Slide 6 Ultrasonic Waves are “Longitudinal Compression Waves” Physics of Acoustic Waves Wave propagation due to elasticity and inertia of the medium. Elasticity counteracts a local compression, return to equilibrium. But, due to inertia return is too large resulting in local rarefaction. Elasticity counteracts a local rarefaction, return to equilibrium. Equilibrium finally reached because of damping These phenomena cause “compression wave” to propagate
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UCSD BE101 Fa06 Lecture 10 Slide 7 “Ultrasonic” relates to the Wave Frequency.
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This note was uploaded on 04/30/2010 for the course BENG 101 taught by Professor Silva,g during the Fall '08 term at UCSD.

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Ultrasound 1 - BE101 Foundations of Biomedical Imaging Fall 2009 David Hall Ph.D Department of Bioengineering University of CaliforniaSan Diego

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