Chapter 8 Q & A

Question 1

given 5 subtances: Backing material, matching layer, PZT, gel and skin, whose impedences have been emasured. The lables have fallen off. Lables are 0.8Mrayls, 1.9Mrayls, 1.6Mrayls, 2.0Mrayls and 1.0Mrayls.

If the impedence of the backing is 1.9Mryals what are the others?

Why

Answer 1

PZT 2.0 Mryals

matching layer 1.6 Mrayls

gel 1.0 Mrayls

skin 0.8 Mrayls

because the impdedences along the path decrease the closer you get to the skin

PZT>matching>backing>gel>skin

Question 2

Pulse length is (directly/incersely) related to pulse duration

Answer 2

directly

Question 3

Q-factor is (directly/inverserly) related to bandwidth

Answer 3

inversely

Question 4

pulse duration is (directly/inversely) related to bandwidth

Answer 4

inversely

Question 5

the sensitivity of transducers that create short duration pulses it likely to be (greather/less/equal to)that of transducers that create long pulses

Answer 5

less than

Question 6

all correctly describe an imaging transducer except

A: high sensitivity

B low Q

C wide bandwidth

D damped

Answer 6

A does not describe imaging transducers

Question 7

shorter duration events (such as damped pulses) are more likely to be wide bandwidth

True/False

Answer 7

true

short duratoin events are likely to be wide bandwidth

Question 8

what occurs when a PZT crystal’s temp is raised above the Curie point

Answer 8

PZt is depolarized and the piezoelectric properties are lost

transducer is ruined

Question 9

the accoustic impedence of the matching layer is approx the same as the accoustic impedance of skin

True/False

Answer 9

False

Question 10

imaging transducers are usually of high rather than low bandwidth

Answer 10

True

Question 11

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

true/false

Answer 11

false

imaging transducers are low Q

Question 12

the damping material in a transducer increases the sensitivy

true/false

Answer 12

false

Question 13

damping material in a transducer increases the pulse length

true/false

Answer 13

false

damping shortens the pulst length

Question 14

damping material in a transducer decreases the pulse duratoin

true./false

Answer 14

true

damping reduces pulse duration

Question 15

damping material in a transducer improves the systems lateral resolutoin

true/false

Answer 15

false

damping does not affect lat res

Question 16

damping material in a transducer improves the systems longitudinal resolution

true/false

Answer 16

true

damping improves longitudinal res

Question 17

damping material in a transducer decreases bandwidth

true/false

Answer 17

false

damping increases bandwidth

Question 18

damping material in a transducer decreases the quality factor

true/false

Answer 18

true

damping decreases the Q factor

Question 19

if the freq of the electrical excitation voltage of a pulsed wave transducer is 6 MHz, then the operating freq of the transducer is 6 MHz

true/false

Answer 19

false

pulsed freq is NOT determined by excitation freq

Question 20

if the pulse repitition freq of a transducer is increased, then the freq of sound produced by the transducer remains the same

true/false

Answer 20

true

Freq and pulse rep are not related

Question 21

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

true/false

Answer 21

false

Question 22

freq of the electrical excitation voltage of a continuous wave transducer is 6 MHz then the operating freq is 6 MHz

True/false

Answer 22

true

Only CW transducers

Question 23

two piezoelectric crystals are made from the same material. The thicker crystal will make a continuous wave transducer with a lower freq

true/false

Answer 23

false

with CW element thickness does not determine sound freq

Question 24

the normal propagatoin speed in piezoelectric material is about 3 to 5 times greater than that is soft tissue

true/false

Answer 24

true

Question 25

the impedance of a transducer active element is 1.9 Mrayls and the impedance of the skin is 1.4 Mrayls

what is an acceptable impedance for the matching layer?

A 1.2 Mrayls

B 1.4 Mrayls

C 1.726 Mrayls

D 1.95 M rayls

Answer 25

C

the impedance of the matching layer is between that of the active element and the skin

Question 26

which of the following crystals will produce sound with the lowest freq?

A thin with low speed

B thin with a high speed

C thick with a low speed

D thick with a high speed

Answer 26

C

lowest freq is produced by thick and slow active element

Question 27

WHich tyupe of transducer has a great Q-factor, therapeutic or imaging

Answer 27

therapeutic

Question 28

which type of transducer has a greater bandwidth, continuous wave or imaging

Answer 28

imaging

Question 29

which type of transducer has more backing material, therapeutic or imaging

Answer 29

imaging

Question 30

in an imaging transducer, what is the purpose of attaching the backing material to the PZT?

A increase bandwidth

B decrease the Q-factor

C improve image quality

D decrease the transducers sensitivity

Answer 30

C

improve image quality

Question 31

a pulsed wave transducer has a resonant freq of 5 MHz. The lowest freq in the pulse is 2 MHz and the highest is 8 MHz. What is the bandwidth?

A 5 MHz

B 8 Mhz

C 3 MHz

D 6 MHz

E 2 MHz

Answer 31

D

bandwidth is the range of freq found in a pulse

8 MHZ-2 MHz=6 MHz

Question 32

for the transducer described in # 25, what is the main freq?

(resonant 5 MHz, low 2 MHz, high 8 MHz)

A 5 MHz

B 8 Mhz

C 3 MHz

D 6 MHz

E 2 MHz

Answer 32

A

the resonant , main or center freq is 5 MHz

Question 33

for the transducer described in # 25, what is the Q-factor

(resonant 5 MHz, low 2 MHz, high 8 MHz)

A 0.8

B 3 MHz

C 5 MHz

D 1.5

E 2 MHz

Answer 33

A

Q-factor is a resonant freq divided by the bandwidth

5 MHz/6 MHz=.8

Band width has no units.