ULTRASOUND TECHNOLOGY History

1. ULTRASOUND TECHNOLOGYHistory • Sonar technology-WWII • Diagnostic tool-1970’s • Now second only to X-rays

2. Advantages of acoustic energy: can be directed in a beam obeys the laws of reflection and refraction reflected off object borders no known unwanted health effects Disadvantages of acoustic energy: propagates poorly through a gaseous medium reflected off of borders of small objects quickly dissipates (as heat) Medical Ultrasound

3. Sound • Human ear can detect frequencies from 20 Hz to 20 KHz • Higher than 20 KHz is ultrasound • Medical Ultrasound 1-20 MHZ • Same transducer sends and receives signals • Assumes speed of sound in body 1540 m/s

4. Ultrasound principle • When you shout into a well, the sound of your shout travels down the well and is reflected (echoes) off the surface of the water at the bottom of the well. If you measure the time it takes for the echo to return ands if you know the speed of sound, you can calculate the depth fairly accurately. d=ct/2

5. Echoes from Two Interfaces

6. Velocity of sound • Dependent on physical make up of material. • Velocity is inversely proportional to compressibility • Directly proportional to density • In body it is almost constant.

7. Tissue Characteristics • Engineers and scientists working in ultrasound have found that a convenient way of expressing relevant tissue properties is to use characteristic (or acoustic) impedance Z(kg/m2s1)

8. Acoustic Impedance • Is fundamental property of matter • Z = Density x Velocity • Unit is Rayls • A.I in Soft Tissue • The Difference determines percentage reflection

9. Interaction Between US & Matter • Reflection • Refraction • Absorption • Scatter

10. Pressure Generation • Piezoelectric crystal • ‘piezo’ means pressure, so piezoelectric means • pressure generated when electric field is applied • electric energy generated when pressure is applied

11. Piezoelectric Principle

12. Transducer Design

13. Characteristics of Piezoelectric crystals • Piezoelectric Effect • Enumerable Dipoles, Changing direction without passing current • Curie Temp. Pierre & Jacques curie 1880 • No Autoclave

15. Ultrasound Image (Embryo)

16. Typical Ultrasound Frequencies: Deep Body 1.5 to 3.0 MHz Superficial Structures 5.0 to 10.0 MHz e.g. 15 cm depth, 2 MHz, 60 dB round trip Why not use a very strong pulse? • Ultrasound at high energy can be used to ablate (kill) tissue. • Cavitation (bubble formation) • Temperature increase is limited to 1º C for safety.

17. The ultrasound that we have described so far presents a two dimensional image, or "slice," of a three dimensional object (fetus, organ). • Two other types of ultrasound are currently in use, 3D ultrasound imaging and Doppler ultrasound. 3D Ultrasound Imaging

18. In the past two years, ultrasound machines capable of three-dimensional imaging have been developed. In these machines, several two-dimensional images are acquired by moving the probes across the body surface or rotating inserted probes.

19. The two-dimensional scans are then combined by specialized computer software to form 3D images.

20. 3D imaging allows you to get a better look at the organ being examined and is best used for:

21. Doppler Ultrasound • Doppler ultrasound is based upon the Doppler Effect. • When the object reflecting the ultrasound waves is moving, it changes the frequency of the echoes, creating a higher frequency if it is moving toward the probe and a lower frequency if it is moving away from the probe.

22. How much the frequency is changed depends upon how fast the object is moving. • Doppler ultrasound measures the change in frequency of the echoes to calculate how fast an object is moving.

23. Doppler ultrasound has been used mostly to measure the rate of blood flow through the heart and major arteries.

24. Ultrasound Doppler Transducer

25. Ultrasound Doppler Principle

26. Ultrasound Doppler Image

27. Major Uses of Ultrasound • Ultrasound has been used in a variety of clinical settings, including obstetrics and gynecology, cardiology and cancer detection. • The main advantage of ultrasound is that certain structures can be observed without using radiation. • Ultrasound can also be done much faster than X-rays or other radiographic techniques.

28. Here is a short list of some uses for ultrasound: • Obstetrics and Gynecology • Cardiology • Urology

29. Obstetrics and Gynecology • measuring the size of the fetus to determine the due date • determining the position of the fetus to see if it is in the normal head down position or breech • checking the position of the placenta to see if it is improperly developing over the opening to the uterus (cervix) • seeing the number of fetuses in the uterus • checking the sex of the baby (if the genital area can be clearly seen)

30. checking the fetus's growth rate by making many measurements over time • detecting ectopic pregnancy, the life-threatening situation in which the baby is implanted in the mother's Fallopian tubes instead of in the uterus • determining whether there is an appropriate amount of amniotic fluid cushioning the baby • monitoring the baby during specialized procedures - ultrasound has been helpful in seeing and avoiding the baby during amniocentesis (sampling of the amniotic fluid with a needle for genetic testing). Years ago, doctors use to perform this procedure blindly; however, with accompanying use of ultrasound, the risks of this procedure have dropped dramatically. • seeing tumors of the ovary and breast

31. Cardiology • seeing the inside of the heart to identify abnormal structures or functions • measuring blood flow through the heart and major blood vessels

32. Urology • measuring blood flow through the kidney • seeing kidney stones • detecting prostate cancer early

33. Dangers of Ultrasound • There have been many concerns about the safety of ultrasound. • Because ultrasound is energy, the question becomes "What is this energy doing to my tissues or my baby?"