Construction and Operation of Transducers

Question 1

Transducers convert what two types of energy?

Answer 1

Electric energy to pressure energy

Question 2

What is it called when crystals are heated to about 350 degrees celsius and then cooled down to allow elements to compress and expand?

Answer 2

Curie point

Question 3

What is operating frequency also called?

Answer 3

Resonance frequency

Question 4

T or F? The operating frequency is different between PW and CW?

Answer 4

True

Question 5

In CW, the operating frequency is determined by what?

Answer 5

The driving voltage

Question 6

In PW, the operating frequency is determined by what?

Answer 6

1. Propagation speed
2. Crystal thickness

Question 7

What is the formula between crystal thickness and operating frequency is PW?

Answer 7

Operating frequency = 1/thickness (inversely proportional)

Question 8

When crystal thickness is increased, what happens to frequency?

Answer 8

Decreases - longer period/wavelength

Question 9

When crystal thickness is decreased, what happens to frequency?

Answer 9

Increases - shorter period/wavelength

Question 10

What is the equation to determine operating frequency in terms of crystal thickness?

Answer 10

F (o) = c / (2x crystal thickness)

Question 11

What type of resolution is improved with harmonics?

Answer 11

Lateral resolution (detail resolution)

Question 12

Benefits of damping material on a transducer?

Answer 12

Decreases SPL (# cycles x wavelength)

Decreases PD (#cycles x period)

Question 13

What element of a transducer decreases the number of cycles in a pulse?

Answer 13

Damping material

Question 14

Does damping material increase or decrease the bandwidth?

Answer 14

Increases / broadens bandwidth

Question 15

What type of resolution is improved with damping material?

Answer 15

Axial and spatial

Question 16

Disadvantages of damping material?

Answer 16

Efficiency and specificity

Question 17

The matching layer thickness is how much of the wavelength of sound leaving the transducer?

Answer 17

1/4 of the wavelength

Question 18

Using ultrasound gel gives rise to what transducer element?

Answer 18

Matching layer - improves transmission

Question 19

What element on the transducer minimizes the acoustic impedance mismatch between transducer crystals and patient tissue?

Answer 19

Matching layer

Question 20

What does CMUT stand for ?

Answer 20

Capacitative Micromachined Ultrasound Transducers

Question 21

The area where the ultrasound beam CONVERGES is known as?

Answer 21

Natural focus

Question 22

What is the near zone also called?

Answer 22

Fresnel zone

Question 23

Beam width decreases with increasing distance from the transducer is called?

Answer 23

Near zone

Question 24

What is the far zone also called?

Answer 24

Fraunhofer

Question 25

Beam width increases with increasing distance from the transducer is called?

Answer 25

Far zone

Question 26

The NZL is also called the?

Answer 26

Focal length

Question 27

What 2 things is the NZL determined by?

Answer 27

1. Operating frequency 2. Size of aperture

Question 28

When frequency increases, what happens to NZL?

Answer 28

Increases

Question 29

When aperture increases, what happens to NZL?

Answer 29

Increases

Question 30

Formula to calculate NZL?

Answer 30

[D^2 x operating frequency] / 6

Question 31

What happens to the NZL when you double the size of the aperture?

Answer 31

Increase by a factor of 4 since it is (D^2)

Question 32

What happens to NZL when you double the frequency?

Answer 32

Increases by a factor of 2

Question 33

Beam focus improves what resolution?

Answer 33

Lateral (detail)

Question 34

What is the focal length?

Answer 34

Distance from transducer to focal region

Question 35

What is the formula to calculate intensity?

Answer 35

Power/Area

Question 36

Where is the HIGHEST intensity of the beam in terms of the focus?

Answer 36

Just before the focus

Question 37

Where is lateral resolution best?

Answer 37

AT or just before focal zone

Question 38

Where should you place the focus to yield the best lateral resolution?

Answer 38

Just below the area of interest

Question 39

What resolution is improved with multiple focuses?

Answer 39

Lateral