73. ULTRASOUNDS: TRANSDUCER

Question 1

1. What is a Transducer?

Answer 1

• this is a probe
• it is any device that converts one form of energy to
  another

Question 2

2. What are the 2 functions of the Ultrasound Transducer?

Answer 2

1. IT IS A TRANSMITTER
   - it produces ultrasounds
   - by converting electrical energy into acoustic energy
2. IT IS A RECEIVER
   - it detects returning ultrasound waves
   - it does this by converting acoustic energy into
   electrical energy

Question 3

3. Why do different Transducer shapes exist?

Answer 3

• they exist to accommodate for which body part is
  being imaged
• the shape of the transducer determines its field of view

Question 4

4. What do High Frequency Transducers image?

Answer 4

• they image superficial structures

Question 5

5. What do Low Frequency Transducers image?

Answer 5

• they image deeper structures

Question 6

6. How do we describe Transducers?

Answer 6

• we describe them by their size
• and by the shape of their footprint

Question 7

7. What does the Transducer act as?

Answer 7

• it acts as the Transmitter of the ultrasound pulses into
  the body

Question 8

8. What needs to be applied to the Transducer before a pulse is transmitted?

Answer 8

A VOLTAGE THAT IS:
- precisely timed
- has a high amplitude

Question 9

9. What is the length of the Ultrasound pulse determined by?

Answer 9

• it is determined by the number of alternating voltage
  changes
• these are applied to the Transducer

Question 10

10. What can Transducers produce?

Answer 10

• they produce a range of frequencies
• these are known as the Bandwidth

Question 11

11. Define the Piezoelectric Effect.

Answer 11

• this is the effect that converts sound waves into
  electrical signals

Question 12

12. Which Greek words can be found in the term: “Piezoelectric”?

Answer 12

• Piezo = “to apply pressure”

Question 13

13. What happens to certain crystals when they are subjected to an electric field?

Answer 13

• they change their physical dimensions

THEY CHANGE BACK TO THEIR INITIAL DIMENSIONS:
- when the field is returned

Question 14

14. What happens to the crystals when they are compressed?

Answer 14

• they can generate electric potentials

Question 15

15. What happens when the voltage, that is applied to a Transducer, changes in polarity (+ or -) ?

Answer 15

• the transducer can change in thickness
• there can also be changes in density

POLARITY CHANGES:
- cause expanding of the transducer
- or contracting of the transducer

Question 16

16. What happens when the transducer changes in thickness and density?

Answer 16

• there are increases and decreases in Pressure
• this produces ultrasound waves
• these are then transmitted into the body

Question 17

17. What causes Pressure changes?

Answer 17

• the returning of the ultrasound echoes

Question 18

18. What happens with these Pressure changes?

Answer 18

• they are converted back into electrical energy signals
• these are transferred to a computer
• they then create an ultrasound image

Question 19

19. What is the wavelength of the ultrasound a function of?

Answer 19

IT IS A FUNCTION OF THE:
- Crystal size

Question 20

20. What is the thickness of the Transducer Crystal inversely related to?

Answer 20

• Frequency