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davies > midterm > Flashcards

midterm Flashcards

1
Q

what array transducer fires all of the elements for each acoustic scan line, using small time delays to steer the beam?

A

phased array

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2
Q

the term signal to noise ratio denotes

A

the relative amplitude of the signal compared to the amplitude of the noise

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3
Q

what technique would be most likely to produce grating lobes in your image?

A

beam steering

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4
Q

during the performance of a sonographic exam, yo would be most likely to encounter refraction in this view

A

curved interface

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5
Q

if you increase the prf and leave all other controls unchanged, what will happen?

A

frame rate with increase

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6
Q

which control is not user adjustable?

A

echo arrival time

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7
Q

you have expanded the image sector width to improve visualization, what can you do to maintain the same temporal resolution

A

decrease the number of focal zones

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8
Q

which control would you adjust to alter the dynamic range of the displayed echoes?

A

compression

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9
Q

what interaction of US and tissue is primarily responsible for imaging internal structure of organs

A

scattering

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10
Q

what can you do to improve the temporal resolution while scanning?

A

decrease the acoustic scan line density

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11
Q

you are imaging a 3D dataset that has anisotropic resolution. what does this mean?

A

unequal resolution is present between imaging planes

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12
Q

what is the advantage of using a water path scanner?

A

near field reverberations are reduced

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13
Q

what type of resolution is determined by the number of pixels in the scan converter?

A

spatial

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14
Q

you are imaging a rounded mass with irregular borders, the mass has a much slower prop speed than the surrounding tissue. what interaction will be encountered?

A

all of the above. refraction, reflection, absorption, scattering

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15
Q

what type of focusing is performed by delay circuitry upon reception?

A

dynamic receive focusing

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16
Q

selective reception of echoes generated within the body by nonlinear propagation describes?

A

tissue harmonic imaging

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17
Q

which helps to improve the Elevational resolution in a B mode image?

A

focusing with an acoustic lens

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18
Q

requirements of magnetic field tracking for 3D reconstruction include which of the following?

A

all of the above

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19
Q

you notice a loss of detail in the lateral dimension of the US image. how do you improve this?

A

increase the scan line density

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20
Q

the US system in your lab has a transducer with a small footprint. what disadvantage does this transducer have?

A

resolution is degraded at large distances

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21
Q

if you wish to use an array transducer that allows you to control transmit focal depth, what type would you select?

A

any of the above

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22
Q

while scanning a curved structure, you notice shadowing at the lateral edges of the structure. what is required for this artifact to occur?

A

different media propagation speeds

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23
Q

all of the following are limitations of M mode scanning except?

A

motion axial to the transducer is not displayed

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24
Q

the spatial resolution of the scan converter is determine by?

A

number of pixels in the scan converter matrix

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25
Q

what information is present in M mode display?

A

time, motion pattern, and amplitude

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26
Q

where are images stored in the US system?

A

scan converter

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27
Q

varying the excitation voltage to each element in the group used to form the US pulse is called?

A

apodization

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28
Q

you have increased the transmit power while performing a pelvic exam, this action increases what?

A

all of the above

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29
Q

which of the following describes an analog signal?

A

continuous variation of the signal is possible

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30
Q

what receiver function is responsible for decreasing the difference between the smallest and largest received signal amplitude?

A

compression

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31
Q

increasing what will improve axial resolution

A

frequency

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32
Q

what control converts numbers stored in memory to proportional voltages?

A

digital to analog converter

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33
Q

what component is necessary for a real time B mode scanner but is not present in A mode?

A

scan converter

34
Q

what is the unit for sound intensity?

A

decibel

35
Q

axial resolution is improved with?

A

all of the above, increased bandwidth, shorter pulse length, and shorter wavelength

36
Q

when you freeze an image, where is the echo information stored?

A

scan converter

37
Q

a digital scan converter is another name for

A

image memory

38
Q

you will not see refraction if…

A

the sound beam is perpendicular to the interface

39
Q

in order to focus a sound beam relatively far away from the transducer, it is advanegeous to?

A

increase the diameter of the element

40
Q

what will not improve axial resolution

A

increased frequency

41
Q

which describes the best resolution for modern day US scanners?

A

axial resolution

42
Q

what benefit would you obtain by choosing a transducer having a large diameter compared to having a small diameter?

A

it can focus at greater depths

43
Q

how do you eliminate grating lobes?

A

reduce or eliminate beam steering

44
Q

increasing the dynamic range setting affects the US image by?

A

decreasing image contrast

45
Q

audible frequency range

A

10kHz

46
Q

Which system function is limited by the speed of sound in tissue?

A

PRF

47
Q

shadowing is a form of what?

A

reflection

48
Q

dynamic receive focusing uses?

A

time delays before echo signals from array elements are combined

49
Q

prop speed error occurs in which sonographic appearance?

A

improper axial resolution of an echo

50
Q

what improves lateral resolution?

A

increased aperature

51
Q

what can you adjust to improve signal to noise ratio?

A

persistence

52
Q

acoustic impedance =?

A

density times prop speed

53
Q

how is electronic noise reduced?

A

rejection

54
Q

when the ac is high?

A

adjust your compensation

55
Q

correct order?

A

transducer, receiver, scan converter, display

56
Q

prop velocity depends on?

A

density and compressibility

57
Q

how many levels can a single bit represent?

A

2

58
Q

which scanning mode doesn’t rely on echo ranging?

A

transmission

59
Q

which least influences axial resolution?

A

beam width

60
Q

the rate of sound attenuation is lowest in?

A

water

61
Q

which artifact will result in both lateral and axial displacement?

A

multipath reflections

62
Q

what would decrease frame rate?

A

increasing acoustic scan line density

63
Q

Dynamic apodization is a method employed to?

A

reduce side lobes

64
Q

attenuation of the sound beam increases with increasing what?

A

all of the above

65
Q

which of the following doesn’t affect impedance?

A

frequency

66
Q

which would increase the SPL?

A

increased number of cycles per pulse

67
Q

for a linear array transducer consisting of a single row of elements, what method is most used to focus the beam in the Elevational direction?

A

mechanical focusing

68
Q

you can reduce the beam width to improve spatial resolution in the image by which of the following?

A

focusing

69
Q

if you increase the PRF, to a level too great for the depth of field, this result will be?

A

range ambiguity

70
Q

what happens when you change the transmit frequency?

A

number of cycles per second is altered

71
Q

what type of resolution is mostly affected by electronic focusing and dynamic aperature?

A

lateral resolution

72
Q

complete destructive interference of echo reflections will affect the display in the following way?

A

by creating black pixels

73
Q

which of the following is not a function of the receiver?

A

dynamic aperature

74
Q

what affect will you detect in the image if you increase the threshold control?

A

decreased appearance of weak echo signals

75
Q

the bands have decreasing brightness with depth, what artifact are you seeing?

A

reverberation

76
Q

what the difference between frequencies used for Doppler and for B mode?

A

the frequency for Doppler is usually lower than for imaging

77
Q

the incoming raw echo signals must be compressed into a smaller dynamic range because?

A

the display cannot accommodate the wide dynamic range of the incoming signals

78
Q

what would you adjust to increase the intensity of the transmitted pulse?

A

output power

79
Q

interference patterns of reflected waves cause?

A

acoustic speckle

80
Q

by increasing the image depth and scan line density, this results in?

A

reduced temporal resolution

81
Q

how can you demonstrate tissue boundaries that are not perpendicular to the sound beam?

A

spatial compounding

82
Q

what is a typical frame rate for B mode real time imaging?

A

10-50 Hz

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