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# SlidesApr20 - different types of tissues by using different...

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A mass m=3 is connected to a spring on its left (spring constant k=2) and an identical spring on its right. What frequency of shaking would produce the largest oscillation of the mass? (Hint: effective spring constant is 2k) Consider the motion of one of the masses Solve the equations of motion Velocity of an ultrasound wave Velocity of the wave is proportional to • This means that waves will travel faster through more rigid tissue that is harder to stretch (higher effective spring constant or “elastic modulus”) and travel slower through denser tissue (higher mass per unit volume). • This variation in speed with tissue type is taken into account by the ultrasound machine when it analyses the reflected waves to form an image. m k What happens when ultrasound waves hit an object or different tissue types in the body 1. Model different density of different types of tissues by using different masses, m 2. Model different elasticity of

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Unformatted text preview: different types of tissues by using different spring constants, k e.g. Air bubble, gallbladder stone, cancerous tumor Reflection of wave pulses from the end of the chain of mass-springs Suppose nothing is beyond the last mass (#N) – like an air bubble in the intestinal tract. Do waves reflect? Detection of Gallbladder stones Hard stones that form in the gallbladder (usually from condensed cholesterol) that can cause intense pain. The stone has a high density and is hard (not very elastic). Gallstones visible inside a surgically removed and sectioned gallbladder. http://en.wikipedia.org/wiki/Gallstone Model as a rigid immovable object that the ultrasound wave hits at the end in our chain of springs. Ultrasound images Fetus Cardiac abnormality Gallbladder stone Why the shadow? Breast tumors Detecting a cancerous tumor (or any other differing tissue type) with ultrasound A simple model:...
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## This note was uploaded on 05/02/2009 for the course PHYS PHYS 1C taught by Professor F during the Spring '00 term at UCSD.

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SlidesApr20 - different types of tissues by using different...

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