82. ULTRASOUNDS: THE DOPPLER PRINCIPLE

Question 1

1. What is the Doppler Principle?

Answer 1

• this is a principle that is used to portray more rapid
  movements
• it looks at the changes from the original frequency to
  the detected frequency

Question 2

2. What is one vital part of the body that we use the Doppler Principle to analyse?

Answer 2

• Blood Flow
• we look at the speed at which it flows

Question 3

3. What does the Doppler Principle relate to?

Answer 3

• it relates to a shift
• this is the shift in the frequency of sound waves

WE LOOK AT HOW THE:
- source of the sound
(the echo)
- moves in relation to the observer

Question 4

4. What is the change in Frequency related to?

Answer 4

• it is related to the velocity of movement
• it enables the velocity of flow to be measured

Question 5

5. What does this image show?

Answer 5

• a Doppler Ultrasound

Question 6

6. In which 3 ways can we represent the flow of blood?

Answer 6

1. A TRACE
   - this shows the change in flow velocity with time
2. THE SOUNDS EMITTED AT FREQUENCIES
   
   • these are equal to the difference between the
     transmitted signals and the returning signals
   • these lie in a range that humans can hear
3. THE SPATIAL DISTRIBUTION OF THE FLOW
   
   • this is portrayed by superimposing the flow
     information
   • this is done in colour
   • it is done on a grey-scale B-Mode image

Question 7

7. What are Colour Flow Images?

Answer 7

• these images show flow velocities
• these flow velocities are indicated by colours
• these colours are seen on specific parts of the
  Ultrasound image

Question 8

8. What do Bright Red colours in Colour images indicate?

Answer 8

• they indicate large flow of blood
• the blood is approaching
• it flows towards the heart

Question 9

9. What do Dim red colours in Colour images indicate?

Answer 9

• they indicate a weak flow of blood
• this is approaching the heart

Question 10

10. What do Blue colours in Colour images indicate?

Answer 10

• they indicate a flow of blood that is receding
• the blood is flowing away from the heart

Question 11

11. What do all colours show in Colour images?

Answer 11

• they show the magnitude of the flow
• they show the direction of the flow
• they show that the blood is moving and flowing

Question 12

12. What do Yellow or green indicate?

Answer 12

• they indicate turbulent flows of blood
• these blood flows lack a well-defined flow direction