Basics of doppler ultrasound imaging for bigannar

2. LecturePreparedfrom TheBurwin’sSPI notesby; Dr.Shah Zaman PhD Ultrasound (Scholar) University of Lahore THE DOPPLER PRRINCIPLE AND INSTRUMENTATION

3. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION 1) General Principles 2) Color Doppler Specific Parameters 3) Power Doppler Imaging 4) Spectral Doppler Specific Parameters 5) Normal flow in Arteries and Veins

4. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION 1)General Principles

5. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION • Christian Andreas Doppler was an Austrian mathematician; he first observed that certain properties of light emitted from stars depend upon the relative motion of the observer and the wave source. • Colored appearance of some stars as due to their motion relative to the earth, the blue ones moving toward earth and the red ones moving away. • He theorized that sound waves from a moving source would be compressed or expanded, or that the frequency would change. • This theory wasn't tested until 1845. • B. Ballot 1845 confirmed Doppler’s with horn players on a train . • Later, a scientist named Fizeau generalized Doppler's work by applying his theory not only to sound but also to light.

6. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION

7. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION OBSERVER 2 Long wavelength Low frequency OBSERVER 1 Small wavelength High frequency

8. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION DOPPLER FREQUENCY SHIFT :– Higher returned frequency if RBCs are moving towards the Transducer and lower if the cells are moving away from transducer

9. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION • Understanding the Doppler equation will enable you to quickly identify the factors that affect the Doppler shift scenario. • Fd is Doppler shifted frequency (what we measure). • V is velocity of RBC (what we want to know). • Ft is transducer (transmitted) frequency . • Cos ϴ is cosine of angle between direction of flow and ultrasound beam. • C is velocity of sound in the body tissues. Fd = 2 Ft V (cosine Ф) C

10. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION THE DOPPLER SHIFT FREQUENCY: • The Doppler shift frequency is the difference between the received frequency and transmitted frequency. • It is directly proportional to transducer frequency.

12. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION Goals of Doppler • Detection of flow in vessel • Detection of flow direction • Detection of flow Type: » Aterial or venous » Normal or abnormal • Measurement of the flow velocity

13. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION Types of Doppler I. Color Doppler. II. Power Doppler III.Pulsed Doppler. IV.Continuous wave Doppler.

14. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION All Doppler Should be performed with I. Gray scale Ultrasound II. Color Doppler III.Power Doppler IV.Pulsed Doppler

15. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION Color specific parameters

16. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION Base line Wall filter Color specific parameters Color Map

41. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION • To perform good Pulsed Doppler you must be able to understand the spectral display. • It is a graphical representation of analyzed Doppler shifts. • It displays three components of the Doppler shift as they occur over time: the direction of the shift, the magnitude of the shift, and the amplitude of the shift.

43. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION • Shift Direction: The baseline on the spectral display separates the positive from negative shifts. Positive shifts are displayed on one side; negative shifts are displayed on the other.

44. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION • Shift Magnitude: This is the size of the shift. Recall the factors on the right side of the Doppler equation. These are the factors that affect the magnitude of the Doppler shift. The two primary factors that affect the magnitude of the Doppler shift are blood velocity and Doppler angle. • The magnitude of the Doppler shift is displayed on the vertical (Y) axis of the spectral display. Higher shifts are displayed farther from the baseline, lower shifts are displayed closer to the baseline. • The magnitude of the Doppler shift is represented on the vertical.

46. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION • Shift Amplitude: This is the strength of the shift. Is it a strong signal or a weak signal? The factors that affect the amplitude of the signal are the same as those that affect the amplitude of any echo: output power, attenuation, acoustic impedance mismatch, type of reflector. However, since the signal is coming from within a small sample volume within moving blood, the primary factor that changes the amplitude of the signal is the number of red blood cells flowing through the sample volume. The more blood, the stronger the signal. The amplitude of the shift is represented by the brightness of the display. Strong shifts are displayed with bright pixels, weaker shifts are displayed with darker pixels.

48. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION • Time: Time is displayed on the horizontal axis. A typical display shows 3-4 seconds along the X axis. • Shift Magnitude: The magnitude of the Doppler shift is displayed on the vertical axis. • Shift Amplitude: The amplitude (strength) of the Doppler shifted echoes is represented by the brightness of the display (Z axis).

52. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION • Baseline: The horizontal baseline separates the positive and negative channels. • Channels: Positive shifts are displayed in the positive channel. Negative shifts in the negative channel. The channels are usually, but not always, indicated by a “positive” and “negative” sign.

53. THE DOPPLER PRRINCIPLE AND INSTRUMENTATION • Nyquist Limit: The Nyquist is the upper limit of each channel. • The Nyquist can be changed by changing the scale.

Basics of doppler ultrasound imaging for bigannar

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