Basic Ultrasound Physics - History Page

	Date/Time	Made By	Edit Note	Type	Scope
	Nov 10 2010, 10:42 PM EST	J12triano		edit	32 words added 125 words deleted 1 image added 1 image deleted
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 View changes from previous version. (Word count: 2049)
	Feb 21 2010, 7:47 AM EST	StuartDurham		edit	50 words added 3 words deleted
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 View changes from previous version. (Word count: 2145)
	Feb 21 2010, 7:18 AM EST	StuartDurham	minor gramatical changes	edit	16 words added 2 words deleted
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 View changes from previous version. (Word count: 2093)
	Jul 9 2008, 9:20 AM EDT	AndyC		edit	12 words added 11 words deleted
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 View changes from previous version. (Word count: 2082)
	Jul 9 2008, 9:19 AM EDT	AndyC		edit	10 words added 31 words deleted
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 View changes from previous version. (Word count: 2081)
	Jul 9 2008, 9:18 AM EDT	AndyC		edit	1137 words added 1 image added
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. View changes from previous version. (Word count: 2094)
	Jul 9 2008, 9:08 AM EDT	AndyC		edit	90 words added
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. ) View changes from previous version. (Word count: 944)
	Jul 9 2008, 9:03 AM EDT	AndyC		edit	2 words added 14 words deleted
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 View changes from previous version. (Word count: 855)
	Jul 9 2008, 9:01 AM EDT	AndyC		edit	128 words added 242 words deleted
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 View changes from previous version. (Word count: 867)
	Jul 9 2008, 8:52 AM EDT	AndyC		edit	1 word added 1 word deleted
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. View changes from previous version. (Word count: 982)
	Jul 9 2008, 8:43 AM EDT	AndyC		edit	5 words added 13 words deleted
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. View changes from previous version. (Word count: 982)
	Jul 9 2008, 8:41 AM EDT	AndyC		edit	374 words added 4 words deleted
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 View changes from previous version. (Word count: 989)
	Jul 9 2008, 8:37 AM EDT	AndyC		edit	24 words added 24 words deleted
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 View changes from previous version. (Word count: 620)
	Jul 9 2008, 8:32 AM EDT	AndyC		edit	2 words added 6 words deleted
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 refractionDefination:- Attenuation View changes from previous version. (Word count: 629)
	Jul 9 2008, 8:31 AM EDT	AndyC		edit	628 words added
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 View changes from previous version. (Word count: 632)
	Jul 9 2008, 8:08 AM EDT	AndyC		create	No content added or deleted.
Change: Created by AndyC Jul 9 2008, 8:08 AM EDT for: no reason given