76. ULTRASOUNDS: FIELDS

Question 1

1. What does a Transducer produce?

Answer 1

• they produce ultrasound pulses
• these make wavefronts
• these wavefronts form a 3D beam of Ultrasound

Question 2

2. What 3 factors does the Characteristic Shape of the beam depend on?

Answer 2

1. The Curvature of the Transducer
2. The Pressure Waves
3. The Acoustic lens that focuses the beam

Question 3

3. What is the function of the Acoustic lens?

Answer 3

• light will enter the lens from many rays
• these rays travel in many different directions
• the lens focuses the beams of light onto the Focal Point

Question 4

4. What is the purpose of the Phased Array Transducer?

Answer 4

• it helps to focus the Ultrasound waves to a specific
  point

Question 5

5. What are the 5 terms that we use to describe the shape and the region of an Ultrasound beam?

Answer 5

1. Focus
2. Near Zone
3. Far Zone
4. Focal Zone
5. Focal length
   (Near length zone)

Question 6

6. What is the Initial Beam Diameter as the beam leaves the Transducer?

Answer 6

• it is the same as the width of the Transducer
• it gets narrower as it gets closer to the focus

Question 7

7. What is the narrowest point of the Ultrasound Beam?

Answer 7

• the focus
• this is found in the Focal zone

Question 8

8. What is the Focal Zone?

Answer 8

• it is the region of the beam that starts to narrow
• this is because of the curvature of the Transducer

Question 9

9. What is the Focal Length?

Answer 9

• it is the equivalent to the length of the Near Zone

Question 10

10. What happens when the sound beam is at a depth that is twice the focal length?

Answer 10

• the sound beam is as wide as the Transducer again

Question 11

11. Label this diagram.

Answer 11

1. Transducer
2. Sound Beam (Wave)
3. Near Zone
4. Focal Zone
5. Far Zone
6. Focus

Question 12

12. What happens when the sound beam exits the Transducer probe?

Answer 12

• it enters the Near Zone
• this is also known as the Fresnel Zone

Question 13

13. What does the Focus mark?

Answer 13

• it marks the end of the near zone
• it marks the beginning of the Far Zone

Question 14

14. What is the Focal Length?

Answer 14

• this is the distance from the Transducer to the focus

IT CAN ALSO BE CALLED THE:
- focal depth
- near zone length

Question 15

15. What is another name for the Far Zone?

Answer 15

• the Fraunhofer Zone

Question 16

16. What happens when the beam reaches the Far Zone (Fraunhofer Zone)?

Answer 16

• it starts to diverge or widen

Question 17

17. What is the Beam Diameter at the Transducer?

Answer 17

• it is equal to the Transducer environment

Question 18

18. What is the Beam Diameter at the Focus?

Answer 18

• it is half the Transducer diameter

Question 19

19. What is the Beam Diameter at 2 near zone lengths?

Answer 19

• it equals the Transducer diameter

Question 20

20. What is the Beam Diameter when the beam is deeper than 2 near zone lengths?

Answer 20

• it is wider than the Transducer diameter