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Jun 2 2012, 7:58 AM EDT
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Change: There were only format changes (bold, italics, etc.) in this version. See this version for details.
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Nov 10 2010, 10:42 PM EST
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Change: The sound that a human ear can hear is usually betweenAudible 20Hz and 20 000Hz. Below 20Hz the wavesInfra aresound calledBelow infra20Hz sound.Ultrasound Above 20 000Hz (20kHz) they are called ultrasound. Ultrasound is high frequency mechanical vibrations or pressure waves
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Feb 21 2010, 7:47 AM EST
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Change: The greater R, the greater the degree of reflection. i.e. R for a soft tissue interface such as liver and kidney is 0.01, i.e. only 1% of the sound is reflected. Muscle/bone interface 40% is reflected and for a soft tissue/air interface 99% is reflected.This is the
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Feb 21 2010, 7:18 AM EST
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Change: waves, the mechanical displacement being in the same direction as propagation.A medium is needed for sound waves to go through, no medium = no soundwaves This propagation is whereby the particles of the medium which the sounds
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Jul 9 2008, 9:20 AM EDT
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AndyC
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Change: each other to form a wavefront wich then determinates the direction of wave travel. The intensity at any point within the beam is determined by the sum of the contributions from all the pointsources. Interferences occurs between the waves from the pointsources, leading to variation in intesityintensity within
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Jul 9 2008, 9:19 AM EDT
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AndyC
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Change: (got this from Roger Gent,1997,Applied Physics and Technology of Diagnostic Ultrasound) "a source of sound acts asif it is composed of an infinite number of point sources of sound. The waves
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Jul 9 2008, 9:18 AM EDT
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AndyC
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Change: Sound speed (c) is equal to one over the square root of the density times compressibility. OR c= square root compressibility / square root density.
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Jul 9 2008, 9:08 AM EDT
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AndyC
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Change: A sound beam is transmitted into a medium and is reflected back from an object. The elapsed time between the transmitted pulse and the received echo is converted into the total distance traveled. (The z value is only half of the distance traveled away and back to the transducer. )
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Jul 9 2008, 9:03 AM EDT
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AndyC
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Change: depth, and frequency decreases linearly with depth. Diffuse Scatter Diffuse scatter occurs when an objects size relative to the wave length becomes smaller. Imagine placing a thin stick upright in
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Jul 9 2008, 9:01 AM EDT
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AndyC
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Change: When a sound wave travels through two mediums of the same density and acoustic impedance the energy of the sound wave travels through the second medium with out loss of energy apart from absorption. However ifOf the is a difference in acoustic impedance or densitythree thereabsorption is
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Jul 9 2008, 8:52 AM EDT
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AndyC
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Change: ImpedenceImpedance is a property of a tissue defined as a product of density of the tissue and velocity of sound in that tissue. Denoted as Z = d ( kg/m3) X c ( m/s2) Reflection co-efficient ( R) is ratio of intensity of reflected wave to incident wave.
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Jul 9 2008, 8:43 AM EDT
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AndyC
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Change: Discussion of each aetiology of attenuationReflection1)When Reflection:Whena sound wave is incident on a interface between two tissues , atissues, part of it is reflected back into the original medium.The amount of energy reflected back depends upon an inherent property of the tissues called impedence.
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Jul 9 2008, 8:41 AM EDT
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AndyC
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Change: When a sound wave travels through two mediums of the same density and acoustic impedance the energy of the sound wave travels through the second
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Jul 9 2008, 8:37 AM EDT
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AndyC
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Change: ******************** UNDER CONSTRUCTION ******************Defining Ultrasound Ultrasound uses sound waves. The sound that a human ear can hear is usually between 20Hz and 20 000Hz. Below 20Hz the
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Jul 9 2008, 8:32 AM EDT
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AndyC
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Change: VariousInteractions interactions of ultrasound with soft tissues When ultrasound wave passes through tissues, 1) There is reduction in amplitude and intensity of ultrasound wave.This is called attenuation . 2) There is change in direction and velocity of the ultrasound wave and this is called refraction Defination:- Attenuation
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Jul 9 2008, 8:31 AM EDT
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AndyC
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Change: Ultrasound uses sound waves. The sound that a human ear can hear is usually between 20Hz and 20 000Hz. Below 20Hz the waves are called
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Jul 9 2008, 8:08 AM EDT
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AndyC
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Change: Created by AndyC Jul 9 2008, 8:08 AM EDT for: no reason given
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