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.

2. Outline History Principles Characteristic Applications National Taiwan University Electrical Engineering Dept.- 2 -

3. History National Taiwan University Electrical Engineering Dept.- 3 - publication of 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 by  non-destructive testing of metals (airplane wings, bridges)  seismology first clinical use for locating brain tumors (Karl Dussik, Friederich Dussik, 1942) the first greyscale images were produced in 1950  in 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

4. Principle – Transducer Piezoelectric National Taiwan University Electrical Engineering Dept.- 4 -

5. Principle – Focusing Lateral Resolution = D = depth, W = wavelength, A = Aperture F number, F# = Ex: f=5Mhz, A = 2cm, V = 1500 m/s In depth 4 cm, resolution = National Taiwan University Electrical Engineering Dept.- 5 -

6. Principle – Focusing (cont’d) Improve  larger aperture  higher frequency (shorter wavelength)  multiple focusing  dynamic focusing National Taiwan University Electrical Engineering Dept.- 6 -

7. Principle – Focusing (cont’d) Improve  larger aperture  higher frequency (shorter wavelength)  multiple focusing  dynamic focusing National Taiwan University Electrical Engineering Dept.- 7 -

8. Principle – Focusing (cont’d) Improve  larger aperture  higher frequency (shorter wavelength)  multiple focusing  dynamic focusing National Taiwan University Electrical Engineering Dept.- 8 -

9. Principle – Effects : Attenuation  The loss of energy in tissue:  f : frequency, z: depth, a0 :attenuation coefficient of medium, typically n=1 Non-linearity  Assuming p was only a tiny disturbance of static pressure  With increasing acoustic pressure, the wave changes shape National Taiwan University Electrical Engineering Dept.- 9 -

10. Principle – Speckle Coherent Imaging system Interference of scatterers National Taiwan University Electrical Engineering Dept.- 10 -

11. Principle – Speckle Scatter size (radius a) Wavelength (λ) Wave number K=2π/λ Optical : ka>>1 Rayleigh : ka<<1 Oscillatory : between National Taiwan University Electrical Engineering Dept.- 11 -

12. Principle – Speckle National Taiwan University Electrical Engineering Dept.- 12 - Rayleigh : ka<<1

13. Principle – Speckle Soft tissue : less than 100μm Independent of scattering structures Dependent of imaging system 、 distance National Taiwan University Electrical Engineering Dept.- 13 -

14. Principle – Speckle Let A be signal received from scatterer with phase θ i, we have: If N→∞, Re{ A } and Im{ A } are asymptotically Gaussian. Joint probability density function: National Taiwan University Electrical Engineering Dept.- 14 -

15. Principle – Speckle Intensity I≡ Re{ A } 2 +Im{ A } 2 So for I ≧ 0: And amplitude E≡ is Rayleigh distribution: National Taiwan University Electrical Engineering Dept.- 15 -

16. Principle – Speckle Define: I 0 is an arbitrary reference signal Expand f: Ignoring R, we have This noise limits the detect ability of low contrast lesions National Taiwan University Electrical Engineering Dept.- 16 -

17. Characteristic Modes  A mode  B mode  M mode  Color Doppler mode Acoustic impedance National Taiwan University Electrical Engineering Dept.- 17 -

18. Characteristic – Modes A mode B mode M mode CPD National Taiwan University Electrical Engineering Dept.- 18 -

19. Applications Diagnostics Therapy 3D 4D National Taiwan University Electrical Engineering Dept.- 19 -

20. Strengths of Ultrasound It images muscles and soft tissues well It’s “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 -

21. Strengths of Ultrasound (cont’d) Equipment is widely available and flexible Portable equipment is available, thus it has high mobility Relatively inexpensive (e.g. X-ray, MRI) National Taiwan University Electrical Engineering Dept.- 21 -

22. Weaknesses of Ultrasound Very limited ultrasound penetrating ability Noisy Low spatial resolution Operator-dependent National Taiwan University Electrical Engineering Dept.- 22 -

23. Dangers of Ultrasound Cavitation Heat generation Bubble formation National Taiwan University Electrical Engineering Dept.- 23 -

24. National Taiwan University Electrical Engineering Dept.- 24 - 參考資料： www.wikipedia.org/wiki/Wiki www.ljbdev.com/speckle.html http://tw.knowledge.yahoo.com/ http://www.cs.sunysb.edu/~mueller/teaching/ http://ultrasound.ee.ntu.edu.tw/chinese.htm http://ultrasound.ee.ntu.edu.tw/belab/course.htm http://www.gehealthcare.com/inen/rad/us/technology/msuwidap.html 特別感謝： 李百旗 教授 鐘孝文 教授 劉建宏 助教

25. Thanks for your attention! National Taiwan University Electrical Engineering Dept.- 25 -