review: Test3

Question 1

Two crystals made of the same material

the thicker crystal will create pulsed ultrasound with what?

(what’s a thicker crystal going to produce?)

Answer 1

thicker PZT crystal will create pulsed ultrasound with slower speeds and low frequency

Question 2

what are the characteristics of imaging transducers?

Answer 2

pulses with short duration and length

uses backing material to limit ringing

reduced sensitivity

wide bandwidth or broadband

lower Q-factor

improved axial resolution

Question 3

what are the characteristics of non-imaging transducers?

Answer 3

creates continuous wave or pulses with long duration and length

no backing material

increased sensitivity

narrow bandwidth

higher Q-factor

cannot even create an image

Question 4

what is the thickness of the matching layer?

Answer 4

1/4 wavelength thick

Question 5

what is the thickness of the active element?

Answer 5

1/2 wavelength thick

Question 6

what happens when PZT exceeds the Curie point?

Answer 6

the crystal’s properties are destroyed (depolarization)

the PZT is depolarized

Question 7

what is the process called when PZT materials change shape?

Answer 7

piezoelectric effect

Question 8

what are all the names for lead zirconate titanate?

Answer 8

PZT, ceramic, active element, crystal, piezoelectric, ferroelectric

Question 9

which component reduces the ringing of the pulse?

Answer 9

backing material (damping element)

Question 10

if we have a transducer with a main frequency of 6MHz, produces a sound pulsed that has frequencies ranging from 1MHz-6MHz, the bandwidth or range of frequency in this pulse is, what?

Answer 10

5MHz

6MHz-1MHz=5MHz

Question 11

How do you calcuate a Q-factor?

Answer 11

quality factor=

main frequency/bandwidth

Question 12

what is the normal propagation speed of piezoelectric material?

Answer 12

the speed of sound in most PZT material ranges from 4-6mm/µs (about 4 times greater than the speed of sound in soft tissue)

Question 13

which crystal will produce sound with a lower frequency and which will produce sound with a higher frequency?

Answer 13

thinner crystals=higher frequency

thicker crystals=lower frequency

Question 14

what is the acoustic impedance of the matching layer?

Question 15

damping material improves the system’s what?

Answer 15

improves axial resolution

Question 16

if the frequency of the electrical excitation voltage of a pulsed transducer is 6MHz, then the operating frequency is, what?

Question 17

what is the impedance of an active element in Rayls?

Answer 17

the impedance of a transducer active element is 1,900,000 Rayls

Question 18

which transducer component has a thin barrier of cork?

Answer 18

acoustic insulator

Question 19

which transducer component increases the efficiency of sound?

Answer 19

matching layer

Question 20

what’s the purpose of having backing material?

Answer 20

it reduces the “ringing” of the PZT

Question 21

factors that affect focal depth:

shallow focus, deep focus

Answer 21

shallow focus- smaller diameter PZT, lower frequency

deep focus- larger diameter PZT, higher frequency

Question 22

how are frequency and near zone length related?

Answer 22

frequency and near zone length are DIRECTLY related

Question 23

two transducers have the same diameter

one probe has a higher frequency than the other, which one has the shallow focus? the deeper focus?

Answer 23

higher frequency-deeper focus

lower frequency-shallow focus

Question 24

with the diameter of the probe and the frequency given, which one will have the least divergence? the most divergence?

Answer 24

less divergence- larger diameter, higher frequency

more divergence- smaller diameter, lower frequency

Question 25

how is the frequency of sound determined?

Answer 25

speed of sound in the PZT

thickness of the PZT

Question 26

how is the focal length determined?

Answer 26

transducer diameter

frequency of the sound

Question 27

how is the spread of the sound beam in the far field determined?

Answer 27

transducer diameter

frequency of the sound

Question 28

with the transducer’s frequency and diameters, which one has the best lateral resolution?

Answer 28

higher frequency and larger diameter= less divergence

(better lateral resolution)

Question 29

with measurement of diameter, where is the focal depth?

Answer 29

transducer diameter and focal depth are DIRECTLY related

focal depth(mm)=

diameter(mm)²/4 x wavelength(mm)

Question 30

if the frequency has not changed and the diameter increases, what will happen to the wavelength?

Answer 30

there is no change to the wavelength

Question 31

if the frequency has not changed and the diameter increases, what will happen to the near zone length?

Answer 31

it increases

Question 32

what determines the spread of the beam in the far field?

Answer 32

transducer diameter

frequency of the sound

Question 33

which one has the shallowest focus?

Answer 33

smallest diameter PZT

lowest frequency

Question 34

which has the deepest focus?

Answer 34

largest diameter PZT

highest frequency

Question 35

which one diverges more?

Answer 35

smallest diameter

lowest frequency

Question 36

which one diverges less?

Answer 36

largest diameter

highest frequency

Question 37

what is the shape of the sound beam that is created by a tiny piece of PZT? what type of pattern is it?

Answer 37

V-shaped waves

spherical, diffraction patterns

Question 38

What are the different names for the different fields on the hour glass?

Answer 38

near zone

focal zone

focus

far zone

Question 39

on the hourglass, where’s the deepest section? most shallow?

Answer 39

deepest- deeper than 2 near zone lengths

most shallow- at the focus