book study questions Test3

Question 1

You are given 5 substances:

backing material, PZT, matching layer, gel, skin

five impedances of:

0.8 Mrayls, 1.9 Mrayls, 1.6 Mrayls, 2.0 Mrayls, 1.0 Mrayls

If the impedance of the backing material is 1.9 Mrayls, what are the impedances of the other four?

Answer 1

The impedance of the active layer is similar to the backing material, so:

backing material-1.9Mrayls

PZT-2.0Mrayls

matching layer-1.6Mrayls

gel-1.0Mrayls

skin-0.8Mrayls

in order of the course of the energy from the PZT through the skin

Question 2

Is pulse length directly or inversely related to pulse duration?

Answer 2

directly

Question 3

Is Q-factor directly or inversely related to bandwidth?

Answer 3

inversely

Question 4

Is pulse duration directly or inversely related to bandwidth?

Answer 4

inversely

Question 5

The sensitivity of transducers that create short duration pulses is likely to be (greater than, less then, or equal to) that of transducers that create long pulses.

Answer 5

less than

Question 6

Describe an imaging transducer:

Answer 6

low sensitivity

low Q

wide bandwidth

damped

Question 7

Shorter duration events (such as dampened pulses) are more likely to be wide bandwidth.

Answer 7

True

Question 8

What occurs when a PZT crystal’s temp is elevated above the Curie point?

Answer 8

the PZT is depolarized

the crystal’s piezoelectric properties are lost and the transducer is ruined

Question 9

The acoustic impedance of the matching layer is approx the same as the acoustic impedance of skin

Answer 9

False

impedance of matching layer is greater than that of the skin

Question 10

Imaging transducers are usually of high rather than low bandwidth

Answer 10

True

Question 11

A very high Q factor transducer is used more often in diagnostic imaging transducers than a low Q factor

Answer 11

False

Imaging transducers are low-Q

Question 12

A pulse with a long pulse duration is likely to have a narrow bandwith

Answer 12

True

Question 13

The damping material in a transducer increases the sensitivity

Answer 13

False

damping reduces sensitivity

Question 14

The damping material in a transducer increases the pulse length

Answer 14

False

damping shortens pulse length

Question 15

The damping material in a transducer decreases the pulse duration

Answer 15

True

Question 16

The damping material in a transducer improves the system’s lateral resolution

Answer 16

False

damping does not affect lateral resolution

Question 17

The damping material in a transducer improves the system’s longitudinal resolution

Answer 17

True

Question 18

The damping material in a transducer decreases the bandwidth

Answer 18

False

damping increases bandwidth

Question 19

The damping material in a transducer decreases the quality factor

Answer 19

True

Question 20

If the frequency of the electrical excitation voltage of a pulsed wave transducer is 6MHz, then the operating frequency of the transducer is 6MHz

Answer 20

False

pulsed wave transducers-frequency of sound is not determined by the elcetrical signal

Question 21

If the pulse repetition frequency of a transducer is increased, then the frequency of sound produced by the transducer remains the same

Answer 21

True

Question 22

The diameter of the active element of a transducer helps to determine the frequency of the sound that the transducer creates

Answer 22

False

Question 23

If the frequency of the electrical excitation voltage of a continuous wave transducer is 6MHz, then the operating frequency of the transducer is 6MHz

Answer 23

True

they are identical with continuous wave transducers

Question 24

Two piezoelectric crystals are made from the same material

The thicker crystal will make a pulsed transducer with a higher frequency

Answer 24

False

thicker active elements create sound with lower frequency, not higher

Question 25

Two piezoelectric crystals are made from the same material the thicker crystal will make a continuous wave transducer with a lower frequency

Answer 25

False continuous wave transducer-active element thickness does not determine the sound beam's frequency

Question 26

The normal propagation speed in piezoelectric material is about 3-5 times greater than that in soft tissue

Answer 26

True

Question 27

The impedance of a transducer active element is 1,900,000 Rayls, and the impedance of skin is 1,400,000 Rayls what is an acceptable impedance for the matching layer?

Answer 27

The impedance of the matching layer should be something in between the active element and the skin

Question 28

What will produce sound with the lowest frequency?

Answer 28

Sound with the lowest frequency is produced by a thick active element with a low speed

Question 29

Which type of transducer has a greater Q-factor: therapeutic or imaging?

Answer 29

Therapeutic

Question 30

Which type of transducer has a greater bandwidth: continuous wave or imaging?

Answer 30

Imaging has a wider bandwith

Question 31

Which type of transducer has more backing material: therapeutic or imaging?

Answer 31

Imaging transducers

Question 32

In an imaging transducer, what is the purpose of attaching the backing material to the PZT? ## Footnote

Answer 32

improve the image quality

Question 33

A pulsed-wave transducer has a resonant frequency of 5MHz the lowest frequency in the pulse is 2MHz and the highest is 8MHz what is the bandwidth?

Answer 33

6MHz bandwidth is the range of frequencies 8MHz-2MHz=6MHz

Question 34

What is the main frequency of a transducer that has a resonant frequency of 5MHz?

Answer 34

the resonant, main, or center frequency is 5MHz

Question 35

What is the Q-factor of a transducer with a resonant frequency of 5MHz and a bandwidth of 6MHz?

Answer 35

0.8 Q-factor is resonant frequency/bandwidth 5MHz/6MHz=0.8 bandwidth has no units

Question 36

A pair of 6MHz probes are identical except for the active element diameter the active element diameters are 6mm and 10mm the sound beam of which probe will have a shallower focus?

Answer 36

probe with a 6mm probe has a shallower focus

Question 37

a pair of 9mm diameter probes are identical except for frequency, which is 3MHz and 6MHz which beam will have a shallower focus?

Answer 37

3MHz beam has a shallower focus

Question 38

what type of beam would create the deepest focus?

Answer 38

probe with the largest diameter and highest frequency gives it the deepest focus

Question 39

what type of probe would create the shallowest focus?

Answer 39

probe with the smallest diameter and lowest frequency will have the shallowest focus

Question 40

active element diameter and near zone length are directly related

Answer 40

true

Question 41

transducer frequency and near zone length are inversely related

Answer 41

false frequency and near zone length are directly related

Question 42

wavelength and near zone length are inversely related

Answer 42

true

Question 43

a pair of 6MHz probes are identical except for the active element diameters, which are 6mm and 10mm which beam will be more compact in the far field?

Answer 43

probe with a 10mm active element has a less divergent beam larger diameter, higher frequency= less divergent

Question 44

a pair of 9mm diameter probes are identical except for frequencies, whcih are 3MHz and 6MHz which sound beam will spread out more in the far field?

Answer 44

3MHz beam is more divergent smaller diameter, lower frequency= more divergent

Question 45

transducer frequency and beam divergence are inversely related

Answer 45

true

Question 46

active element diameter and beam divergence are inversely related

Answer 46

true

Question 47

the frequency of a transducer does not change if the diameter of the new piezoelectric crystal increases, what happens to the near zone length?

Answer 47

increases

Question 48

the frequency of a transducer does not change ## Footnote if the diameter of the new piezoelectric crystal increases, what happens to the beam diameter in the far zone?

Answer 48

decreases

Question 49

the frequency of a transducer does not change if the diameter of the new piezoelectric crystal increases, what happens to the wavelength?

Answer 49

no change

Question 50

the frequency of a transducer does not change if the diameter of the new piezoelectric crystal increases, what happens to the beam diameter in the near zone?

Answer 50

increases

Question 51

what is the shape of a sound beam created by a tiny piece of PZT?

Answer 51

V-shaped

Question 52

what explains why a sound beam created by a disc-shaped crystal is hourglass shaped?

Answer 52

Huygens' Principle

Question 53

what is the deepest location in a sound beam?

Answer 53

the end of the Fraunhofer zone