review: Test3 Flashcards

1
Q

Two crystals made of the same material

the thicker crystal will create pulsed ultrasound with what?

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

A

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

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2
Q

what are the characteristics of imaging transducers?

A

pulses with short duration and length

uses backing material to limit ringing

reduced sensitivity

wide bandwidth or broadband

lower Q-factor

improved axial resolution

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3
Q

what are the characteristics of non-imaging transducers?

A

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

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4
Q

what is the thickness of the matching layer?

A

1/4 wavelength thick

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5
Q

what is the thickness of the active element?

A

1/2 wavelength thick

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6
Q

what happens when PZT exceeds the Curie point?

A

the crystal’s properties are destroyed (depolarization)

the PZT is depolarized

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7
Q

what is the process called when PZT materials change shape?

A

piezoelectric effect

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8
Q

what are all the names for lead zirconate titanate?

A

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

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9
Q

which component reduces the ringing of the pulse?

A

backing material (damping element)

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10
Q

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?

A

5MHz

6MHz-1MHz=5MHz

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11
Q

How do you calcuate a Q-factor?

A

quality factor=

main frequency/bandwidth

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12
Q

what is the normal propagation speed of piezoelectric material?

A

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)

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13
Q

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

A

thinner crystals=higher frequency

thicker crystals=lower frequency

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14
Q

what is the acoustic impedance of the matching layer?

A
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15
Q

damping material improves the system’s what?

A

improves axial resolution

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16
Q

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

17
Q

what is the impedance of an active element in Rayls?

A

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

18
Q

which transducer component has a thin barrier of cork?

A

acoustic insulator

19
Q

which transducer component increases the efficiency of sound?

A

matching layer

20
Q

what’s the purpose of having backing material?

A

it reduces the “ringing” of the PZT

21
Q

factors that affect focal depth:

shallow focus, deep focus

A

shallow focus- smaller diameter PZT, lower frequency

deep focus- larger diameter PZT, higher frequency

22
Q

how are frequency and near zone length related?

A

frequency and near zone length are DIRECTLY related

23
Q

two transducers have the same diameter

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

A

higher frequency-deeper focus

lower frequency-shallow focus

24
Q

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

A

less divergence- larger diameter, higher frequency

more divergence- smaller diameter, lower frequency

25
how is the frequency of sound determined?
speed of sound in the PZT thickness of the PZT
26
how is the focal length determined?
transducer diameter frequency of the sound
27
how is the spread of the sound beam in the far field determined?
transducer diameter frequency of the sound
28
with the transducer's frequency and diameters, which one has the best lateral resolution?
higher frequency and larger diameter= less divergence (better lateral resolution)
29
with measurement of diameter, where is the focal depth?
transducer diameter and focal depth are DIRECTLY related focal depth(mm)= diameter(mm)2/4 x wavelength(mm)
30
if the frequency has not changed and the diameter increases, what will happen to the wavelength?
there is no change to the wavelength
31
if the frequency has not changed and the diameter increases, what will happen to the near zone length?
it increases
32
what determines the spread of the beam in the far field?
transducer diameter frequency of the sound
33
which one has the shallowest focus?
smallest diameter PZT ## Footnote lowest frequency
34
which has the deepest focus?
largest diameter PZT highest frequency
35
which one diverges more?
smallest diameter lowest frequency
36
which one diverges less?
largest diameter highest frequency
37
what is the shape of the sound beam that is created by a tiny piece of PZT? what type of pattern is it?
V-shaped waves spherical, diffraction patterns
38
What are the different names for the different fields on the hour glass?
near zone focal zone focus far zone
39
on the hourglass, where's the deepest section? most shallow?
deepest- deeper than 2 near zone lengths most shallow- at the focus