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Ultrasound In Medicine

Ultrasound In Medicine. Chapter- 3. Ultrasound instrumentation. Modes of ultrasound imaging. 0. 2. 4. 6. 8. 10. A- Scan (Pulsed Scan). Echoes are shown in screen as pulses Give us information about the diameter of structures Is one dimensional Transducer is fixed. f. initial

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Ultrasound In Medicine

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  1. Ultrasound In Medicine Chapter- 3 Ultrasound instrumentation

  2. Modes of ultrasound imaging.

  3. 0 2 4 6 8 10 A- Scan (Pulsed Scan) • Echoes are shown in screen as pulses • Give us information about the diameter of structures • Is one dimensional • Transducer is fixed f initial pulse back surface echo crack echo crack plate UT Instrument Screen

  4. A- Scan (pulsed Scan) • It is used to obtain diagnostic information about the depth of structures in the body by measuring the time required to receive the reflec­ted sound (echoes) from the various surfaces in the body.

  5. A- Scan (pulsed Scan) The amount of reflection depends upon 1- the difference in the acoustical impedances of the two media 2- the orientation of the surface with respect to the beam. The most intense detected signals are due to reflections from surfaces perpendicular to the beam.

  6. Medical Application of A-scan Detection of Brain Tumors (encephalography) The usual procedure is to compare the echoes from the left side of the head to those from the right side and to look for a shift in the midline structure. a shift of more than 3 mm for an adult or 2 mm for a child is considered abnormal.

  7. Medical Application of A-scan Frequencies in the range 1 -5 MHz is used in the medical application due to bone absorption • In the application of A-scan in detecting eye disease. Frequencies up to 20 MHz can be used to produce better resolution. Reason: there is no bone to absorb most of the energy and absorption is not significant because the eye is small

  8. B-Scan (Brightness Mode) • Echoes are shown in screen as points • We can see the aspect مظهر of tissues and organs • Is two dimensional • Movable transducer

  9. B-scan on Oscilloscope is known as Grey scale display • the brightness is directly proportional to the size of the echo,large echoes appear brighter than weak echoes. • The advantage :it is successful in detecting tumors such as liver tumors.

  10. M-Scan (motion scan) • The transducer is held stationary as in the A scan and the echoes appear as a dotsas in the B scan. • One of important medical applications is M-scans of mitral valves • information of interest is the rate of closing of the mitral valve الصمام الميترالي

  11. atrium heart valves ventricle Ultrasound imaging:imaging the heart

  12. M-Scan (motion scan) • The rate of closing for a normal valve is 72 mm/sec • M-scan showing an abnormality called mitral-stenosis (narrowing of the valve opening) • The slower the rate of closure, the larger the amount of stenosis.

  13. Doppler Effect • The frequency change due to the motion of the source or listener is called the doppler effect. • The difference in frequency caused by the motion of the source or listener or both is called the Doppler shift

  14. Medical Application of Doppler Effect When the sound is reflected from the red blood cells, its Frequency is changed in a kind of Doppler effect because the cells are moving.

  15. The ultrasound probe emits an ultrasound wave • A stationary blood cell reflects the incoming wave with the same wavelength: there is no Doppler shift

  16. The ultrasound probe emits an ultrasound wave A blood cell moving away from the probe reflects the incoming wave with a longer wavelength In reality, there is actually two Doppler shifts. The first one occurs between the probe and the moving blood cell (not shown here) and the second one occurs as the red blood cell reflects the ultrasound.

  17. Doppler effect: blood flow in artery

  18. Medical Application of Doppler Effect • The Doppler effect can be used to measure the velocity of moving objects or fluids within the body such as the blood • v is velocity of sound • U is velocity of blood

  19. Summery of USHow it works… A thin layer of jelly is placed between the probe and the skin to make sure all the sound enters the body. • The probe contains a transmitter and a receiver. Ultrasound probe A pulse of ultrasound is sent out by the transmitter. The pulse is reflected from a surface and returns to the receiver. skin The ultrasound machine measures how long it takes for the pulse to return Body tissue (muscle etc)

  20. Advantages • It performs muscles and soft tissue images very well. • It renders "live" images. • It shows the structure of organs. • Small, easily carried scanners are available.

  21. It has no known long-term side effects and rarely causes any discomfort to the patient. Equipment is widely available and comparatively flexible.

  22. Disadvantages • Ultrasound devices have trouble penetrating bone. • Ultrasound performs very poorly when there is a gas between the scan head and the organ of interest. • The deep penetration of ultrasound is limited. • The method is operator-dependent.

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