Ultrasound-EBME410-2

Ultrasound-EBME410-2 - Cardiac Imaging EBME410/320...

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1 EBME410/320 Ultrasound imaging II (imaging) David L. Wilson Some slide materials courtesy of Dr. Cheri Deng, U Mich. Cardiac Imaging Speckle noise 4-chamber view 30 frame/sec Image in a “window” PULSE GENERATOR POWER AMPLIFIER TRANSDUCER T/R Switch Medium Basic Ultrasound System Transmit RF AMPLIFIER DIGITIZER Receive Processor to create image Specular surface λ >boundary variation Non-specular surface λ < boundary variation Small scatterers within a medium, λ ~ particle size Interaction of Sound with Materials
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2 Secular Reflection/Refraction Sound reflected from specular surface might not return to transducer! Signal Display A-scan : Display of echo Amplitudes from single scan line M-scan : Display of Motion from a series of scan lines in time at one location in space B-scan : Display of Brightness from a series of scan lines in space at one duration in time Eye is mostly echolucent Location of scatter= Time delay*(sound speed)/2 Amplitude (grays-scale contrast)= scatterers properties (size, impedance, etc.) Axial resolution: pulse length (ultrasound frequency and bandwidth) A-mode T
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3 Real time gray scale image display of a ollection of A-lines obtained by linearly scanning the ultrasound transmitted pulses via physical scanning or electronically scanning of the beam Image quality: Axial imaging resolution : pulse length (frequency and frequency bandwidth) Lateral imaging resolution : 3-dB beam width (frequency, focusing) Image contrast : inherent (endogenous) tissue properties, novel signal processing schemes B-mode RF AMPLIFIER RECTIFIER VIDEO SIGNAL PROCESSOR VIDEO DISPLAY envelope signal rf signal Forming B-mode Image Ultrasound generation and detectio: Transducers Single Element Transducers • Fixed beam characteristics • Mechanical scanning Arrays Transducers • Electronic steering of beams • Variable focal depth Transducers Piezoelectric effect used to convert electrical signal to acoustical signal Active element thickness is ½ natural wavelength • Optimal impedance matching is achieved by a matching layer thickness of ¼ wavelength Backing reduces pulse length to improve spatial resolution • Commonly used materials include
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This note was uploaded on 01/16/2011 for the course EBME 320 taught by Professor Mult during the Fall '10 term at Case Western.

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Ultrasound-EBME410-2 - Cardiac Imaging EBME410/320...

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