生醫工程實驗 期中報告 Ultrasound.ppt

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1、生醫工程實驗 期中報告Ultrasound,Apr. 2 2007第一組：郭昱昇溫仁揚溫昌懌,National Taiwan University Electrical Engineering Dept.,Outline,HistoryPrinciplesCharacteristicApplications,National Taiwan University Electrical Engineering Dept.- 2 -,History,National Taiwan University Electrical Engineering Dept.- 3 -,publication of

2、The Theory of Sound (Lord Rayleigh, 1877)discovery of piezo-electric effect (Pierre Curie, 1880)enabled generation and detection of ultrasonic waves first practical use in World War One for detecting submarines followed bynon-destructive testing of metals (airplane wings, bridges)seismology first cl

3、inical use for locating brain tumors (Karl Dussik, Friederich Dussik, 1942) the first greyscale images were produced in 1950in real time by Siemens device in 1965 electronic beam-steering using phased-array technology in 1968 popular technique since mid-70s substantial enhancements since mid-1990,Pr

4、inciple Transducer,Piezoelectric,National Taiwan University Electrical Engineering Dept.- 4 -,Principle Focusing,Lateral Resolution = D = depth, W = wavelength, A = ApertureF number, F# = Ex: f=5Mhz, A = 2cm, V = 1500 m/sIn depth 4 cm,resolution =,National Taiwan University Electrical Engineering De

5、pt.- 5 -,Principle Focusing (contd),Improve larger aperture higher frequency (shorter wavelength) multiple focusing dynamic focusing,National Taiwan University Electrical Engineering Dept.- 6 -,Principle Focusing (contd),Improve larger aperture higher frequency (shorter wavelength) multiple focusing

6、 dynamic focusing,National Taiwan University Electrical Engineering Dept.- 7 -,Principle Focusing (contd),Improve larger aperture higher frequency (shorter wavelength) multiple focusing dynamic focusing,National Taiwan University Electrical Engineering Dept.- 8 -,Principle Effects :,AttenuationThe l

7、oss of energy in tissue:f : frequency, z: depth , a0 :attenuation coefficient of medium , typically n=1Non-linearityAssuming p was only a tiny disturbance of static pressureWith increasing acoustic pressure , the wave changes shape,National Taiwan University Electrical Engineering Dept.- 9 -,Princip

8、le Speckle,Coherent Imaging systemInterference of scatterers,National Taiwan University Electrical Engineering Dept.- 10 -,Principle Speckle,Scatter size (radius a)Wavelength () Wave number K=2/Optical : ka1Rayleigh : ka1Oscillatory : between,National Taiwan University Electrical Engineering Dept.-

9、11 -,Principle Speckle,National Taiwan University Electrical Engineering Dept.- 12 -,Rayleigh : ka1,Principle Speckle,Soft tissue : less than 100mIndependent of scattering structuresDependent of imaging system、distance,National Taiwan University Electrical Engineering Dept.- 13 -,Principle Speckle,L

10、et A be signal received from scatterer with phase i , we have:If N , Re A and Im A are asymptotically Gaussian.Joint probability density function:,National Taiwan University Electrical Engineering Dept.- 14 -,Principle Speckle,Intensity I Re A 2 +Im A 2,So for I0:,And amplitude E is Rayleigh distrib

11、ution:,National Taiwan University Electrical Engineering Dept.- 15 -,Principle Speckle,Define: I0 is an arbitrary reference signalExpand f:Ignoring R , we have,This noise limits the detect ability of low contrast lesions,National Taiwan University Electrical Engineering Dept.- 16 -,Characteristic,Mo

12、desA modeB modeM modeColor Doppler modeAcoustic impedance,National Taiwan University Electrical Engineering Dept.- 17 -,Characteristic Modes,A modeB modeM modeCPD,National Taiwan University Electrical Engineering Dept.- 18 -,Applications,DiagnosticsTherapy3D4D,National Taiwan University Electrical E

13、ngineering Dept.- 19 -,Strengths of Ultrasound,It images muscles and soft tissues wellIts “Live”Non-invasive It has no known long-term side effects, and it causes rarely discomfort to patient,National Taiwan University Electrical Engineering Dept.- 20 -,Strengths of Ultrasound (contd),Equipment is w

14、idely available and flexiblePortable equipment is available, thus it has high mobilityRelatively inexpensive (e.g. X-ray, MRI),National Taiwan University Electrical Engineering Dept.- 21 -,Weaknesses of Ultrasound,Very limited ultrasound penetrating ability NoisyLow spatial resolutionOperator-depend

15、ent,National Taiwan University Electrical Engineering Dept.- 22 -,Dangers of Ultrasound,CavitationHeat generationBubble formation,National Taiwan University Electrical Engineering Dept.- 23 -,National Taiwan University Electrical Engineering Dept.- 24 -,參考資料：www.wikipedia.org/wiki/W http:/ http:/www.cs.sunysb.edu/mueller/teaching/http:/ultrasound.ee.ntu.edu.tw/chinese.htmhttp:/ultrasound.ee.ntu.edu.tw/belab/course.htmhttp:/ 教授鐘孝文 教授劉建宏 助教,Thanks for your attention!,National Taiwan University Electrical Engineering Dept.- 25 -,