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Ultrasound Physiscs > SPI Practice Exam 1 > Flashcards

SPI Practice Exam 1 Flashcards

1
Q

A longitudinal wave is characterized by __________.

A

particle motion in same direction as the direction of wave propagation

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2
Q

Pulsed-wave operation is necessary for B-mode imaging because:

A

the depth to the reflector can be determined

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3
Q

The output power of an ultrasound pulser determines the _________ of the acoustic pulse.

A

Intensity

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4
Q

What can be said of the Doppler shift when the sound beam is parallel to the direction of travel of the red blood cells

A

It is at a maximum

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5
Q

*The half-value-layer (or the half-intensity-depth) of a 3 MHz transducer

A

2 cm

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6
Q

Two ultrasound transducers are used to perform Doppler exams on the same patient. The settings are identical except that the transducer frequencies are 5 and 2.5 MHz. Which exam will produce the highest frequency shifts?

A

5.0 MHz

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7
Q

Assuming soft-tissue, what is the amount of attenuation of sound from a 5 MHz transducer after traveling through 1 cm?

A

2.5 dB

*attenuation coefficient = 1/2f

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8
Q

Which of the following transducers provides the maximum penetration?

A

2.25 MHz

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9
Q

What is the primary disadvantage of multiple focal zones along each scan line of a two-dimensional image?

A

Decreased temporal resolution

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10
Q

What happens to a digital image when the pixel density is increased?

A

There is more spatial detail in the display

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11
Q

Which of the following produces a rectangular format?

A

Linear sequenced array

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12
Q

Increasing the gain generally produces the same effect on the image as

A

Increasing the output power

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13
Q

The speed of ultrasound in soft tissue is closest to

A

1540 m/s

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14
Q

A video display that is limited to only black and white, with no other shades of gray, is called _______

A

Bistable

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15
Q

Which Doppler function controls how many waveforms are displayed on the image at one time?

A

sweep speed

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16
Q

*Sound power is measured in units of….

A

Watts

*note: talking about power

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17
Q

Which of the following will reduce/eliminate aliasing?

A

Increase the Nyquist limit above the Doppler shift

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18
Q

*Review

What receiver function converts the negative portion of the RF signal to positive?

A

Rectification

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19
Q

You are using a transducer that produces a beam with a very wide elevational plane. Which of the following problems are you most likely to encounter as a result?

A

Slice thickness artifact

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20
Q

Damping in a transducer

A

reduces the number of cycles in a pulse

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21
Q

Looking at this image, what type of image mode was used?

  1. M mode
  2. A mode
  3. B mode
  4. Amplitude mod
A

M mode

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22
Q

What principle states that sound is generated from the transducer as wavelets?

A

Huygen’s

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23
Q

*If the amplitude is decreased by 50%, what is the corresponding change in power?

A

-6 dB

*note: review amplitude!

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24
Q

Pulse duration is the ______ it takes for one ______ to occur

A

time; pulse

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25
Q

Which of the following describes Snell’s Law?

A

Law that describes the angle of a transmitted beam

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26
Q

A small (relative to the wavelength) reflector is said to __________ an incident sound beam

A

scatter

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27
Q

The axial resolution is primarily determined by:

A

spatial pulse length

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28
Q

Focusing…

A

Improves lateral resolution

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29
Q

With phased array transducers, the transmitted sound beam is swept by

A

varying the timing of pulses to the individual piezoelectric elements

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30
Q

What is the component of an ultrasound system that is made out of lead zirconate titanate?

A

Transducer’s active element

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31
Q

Assuming a fixed frequency, what happens if the diameter of an unfocused transducer is increased?

A

the length of the near zone increases

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32
Q

Avoiding a local temperature increase exceeding _____ should ensure that are no thermally induced biological effects

A

2° C

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33
Q

Manufacturing a transducer with more damping…

A

reduces the duty factor

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34
Q

Which of the following will improve a system’s temporal resolution?

A

Increased PRF

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35
Q

*Review

Which of the following tasks is incorporated in the process of demodulation?

A

Rectification

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36
Q

Which of the following frequencies is in the “ultrasound” range?

A

1.5 MHz

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37
Q

Which of the following is a characteristic of the medium through which a sound is propagating?

A

impedance

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38
Q

*Which one of the following statements is true about a single pulse of ultrasound emitted by a transducer?

A

It contains a range of frequencies

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39
Q

Images magnified using ________ will have better quality due to preservation of the pixel density.

A

write zoom

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40
Q

Diagnostic ultrasound frequency range is:

A

2 to 20 MHz

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41
Q

Parenchyma appears on ultrasound as a pattern of gray dots. This interference pattern is a result of

A

acoustic speckle

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42
Q

*The frequency of a CW transducer is determined by

A

the frequency of the oscillator

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43
Q

What testing device is used to measure acoustic output (intensity) level?

A

Hydrophone

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44
Q

If the imaging depth is increased and the sector angle and line density remain the same:

A

the frame rate decreases

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45
Q

Spatial pulse length equals the number of cycles in a pulse multiplied by:

A

wavelength

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46
Q

Which of the following is NOT a method in which venous flow returns to the heart?

A

left ventricle contraction

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47
Q

What is the smallest element in a digital picture called?

A

The pixel

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48
Q

If the power of a wave is halved, the intensity ___________ its original value.

A

Is reduced to one-half its original value

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49
Q

The image is brighter at the level of the focal zone. Which of the following controls is best to correct this?

A

TGC

50
Q

What is the difference between audible sound and ultrasound?

A

Ultrasound has a higher frequency

51
Q

The propagation speed is highest in

A

bone

52
Q

*Review

Two ultrasound systems produce pulses. One pulse is 0.4 µs in duration and the other is 0.2 µs. Which pulse is most likely to produce the best radial resolution?

A

0.2 μsec system

53
Q

Which of the following will not demonstrate aliasing of the Doppler signal?

A

Power Doppler

54
Q

Which of the following is representative of the duty factor for continuous-wave (CW) ultrasound?

A

100%

55
Q

With oblique or normal incidence, the angle of reflection always equals

A

the angle of incidence

56
Q

The redirection of sound energy in many directions as a result of a rough boundary between two media is

A

scattering

57
Q

*Review dB

If the operator increases the acoustic output of the machine by 20 dB, the beam intensity is increased by

A

100 times

58
Q

The piezoelectric effect describes how _______ is converted into ________ by a ________.

A

ultrasound; electricity; transducer

59
Q

Which Doppler control rejects noise along the baseline?

A

Wall filter

60
Q

The fundamental operating principle of medical ultrasound transducers is:

A

piezoelectric effect

61
Q

*Review TDR

A 1.5D transducer has what ability?

A

Electronically focus in the elevational plane

62
Q

*Review

A decrease in power or intensity by a factor of 2 represents a change of

A

-3 dB

63
Q

If the line density changes but the imaging depth remains the same, what else must change?

A

frame rate

64
Q

*Review

The density is the same in materials A and B, but the speed of sound in material B is 10% greater than the speed of sound in material A.

A

The acoustic impedance in B is 10% greater than the acoustic impedance in A

65
Q

A decrease in the thickness of a piezoelectric element will result in

A

an increase in the frequency of the transducer

66
Q

*Read question carefully!

*If red blood cells are traveling toward a transducer, the frequency emitted by the transducer is _____ the frequency reflected from the red blood cells

A

Less than

67
Q

*Which of the following do the source and the medium determine?

A

axial resolution

68
Q

Ultrasound energy is traveling through the soft-tissue. If the frequency is doubled, the propagation speed is

A

Unchanged

69
Q

For perpendicular incidence, if the impedances of the media are the same, there will be no…

A

Reflection

70
Q

The area between the face of an unfocused single-element transducer and the point where the beam starts to diverge is the

A

Fresnel zone

71
Q

Axial resolution is affected by all of the following EXCEPT

A

focusing

72
Q

Which of the following has time represented on the X-axis?

A

M mode

73
Q

What is the term for adjusting the displayed brightness of the dots as they relate to attenuation?

A

Compensation

74
Q

Which of the following will produce a transducer with a high Q-factor?

A

Continuous-wave transducer

75
Q

Longitudinal resolution is also called

A

Axial

76
Q

During a PW Doppler exam, aliasing is noted by the sonographer. Which of the following will decrease the likelihood of aliasing?

A

Selection of another imaging view that provides a decrease in the pulse repetition period

77
Q

In real-time imaging the transmitted ultrasound beam is not continuously generated, but is pulsed. Approximately what fraction of time is the transducer actively generating sound waves?

A

1%

78
Q

Lateral resolution is determined mainly by

A

beam diameter

79
Q

As frequency is increased:

A

a three-cycle ultrasound pulse decreases in length

80
Q

If the frequency is doubled…

A

the spatial pulse length will be one-half

81
Q

*Why is the digital to analog (D to A) converter needed?

A

The scan converter signal is digital and needs to be converted to analog

82
Q

*Review

The acoustic impedance of a matching layer in a transducer should have a value

A

between the acoustic impedance of the piezoelectric element and the acoustic impedance of tissue

83
Q

*Review

*Which of the following will create the fastest speed of sound?

A

Low density, high stiffness

84
Q

*Review

Higher frequency transducers provide

A

improved lateral resolution

85
Q

Far zone beam divergence can be reduced on a single-element transducer by using

A

a higher frequency transducer

86
Q

What must be known in order to calculate distance to a reflector?

A

Travel time, propagation speed

87
Q

Increasing the operating frequency:

A

improves spatial resolution

88
Q

Which of the following is a true statement?

A

Most ultrasound machines have better axial resolution than lateral resolution

89
Q

*Watch out for spelling

Ultrasound waves that are traveling through a medium consist of

A

compressions and rarefactions

90
Q

The particles in a medium vibrate in a ______________ motion under the influence of a sound wave

A

Longitudinal

91
Q

Which of the following is proportional to the square of the amplitude?

A

Power

92
Q

*Review

The average attenuation of ultrasound energy in the patient is approximately

A

0.7 dB per cm per MHz

93
Q

If the real time frame rate is increased and the lines per frame are unchanged, what else must happen?

A

imaging depth decreases

94
Q

Relative sound intensity based on a logarithmic scale is expressed typically in units of:

A

decibel

95
Q

An unfocused, single-element disc transducer that is 13mm in diameter has a diameter at the focal zone of:

A

6.5 mm

96
Q

The “useful” artifact that one might see behind a weakly attenuating structure:

A

Enhancement

97
Q

If the number of cycles in a pulse is reduced….

A

The pulse duration is reduced

98
Q

*Review TDR

Which of the following transducers fire the elements, in groups, in sequence?

A

linear sequenced array

99
Q

If you wish to practice the ALARA principle, which of the following techniques should you employ?

A

Use the lowest transmit power that allows adequate tissue visualization

100
Q

The minimum reflector separation required to produce separate echoes parallel to the beam is…

A

the radial resolution of the transducer

101
Q

With 6 bits, what is the largest number of different shades of gray that can be stored?

A

64

102
Q

*Review

Which type of display has two polarized filters in front of a light source with crystals that twist and untwist?

A

Liquid Crystal Display

103
Q

*Review

A decrease in power or intensity by a factor of 2 represents a change of

A

-3 dB

104
Q

Which transducer has the best axial resolution?

A

2 cycles/pulse, 4MHz

105
Q

*Which of the following terms does not belong with the others?

A

Decreased spatial pulse length

.

106
Q

Review

*The typical range of pulse repetition frequencies in a pulse-echo ultrasound system is

A

4,000 Hz to 15,000 Hz

.

107
Q

Review

*Which of the following artifacts adds additional reflectors to the image?

A

Reverberation

.

108
Q

What is the name of the ultrasound technology used to measure the hardness of a mass lesion?

A

Elastography

.

109
Q

*Review

Which of the following is true regarding shades of gray in a B-mode image?

A

The more bits assigned to each pixel, the more shades of gray available

.

110
Q

*Review

The attenuation of 5 MHz ultrasound in 4cm of soft tissue is:

A

10 dB

111
Q

If the number of lines per frame is kept constant, but the pulse repetition frequency is doubled, what is the effect on the maximum frame rate?

A

doubled

112
Q

Which of the following provides for a wider field of view and a larger/longer image?

A

Extended field of view imaging

113
Q

*Review

An array transducer with electronic focusing will have what characteristic in the firing pattern of the elements?

A

There will be a curvature in the firing pattern

114
Q

As the frequency of sound increases…

A

the amount of scatter is increased

115
Q

*Review

Side lobe artifact results from which of the following?

A

Acoustic energy radiating in a different direction other than the beam’s main axis

116
Q

*Which of the following is a characteristic(s) of non-specular reflectors?

A

they provide the internal texture of organs in B-mode imaging

117
Q

Review

*The resonant frequency of a pulsed-wave ultrasound transducer is dependent on

A

he thickness of the piezoelectric element and the speed of sound through the piezoelectric element

118
Q

Which of the following does NOT affect lateral resolution?

A

bandwidth

119
Q

If no refraction occurs as an oblique sound beam passes through the boundary between two materials, what must be identical between the two materials?

A

Propagation speed

120
Q

Which of the following has the highest relative attenuation?

A

air

Ultrasound Physiscs (18 decks)

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