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RA6007 > Ultrasound > Flashcards

Ultrasound Flashcards

1
Q

Sound is a longitudinal wave

A

T

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2
Q

Sound requires a medium for propagation

A

T

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3
Q

Sound can propagate in a vaccuum

A

F (sound travels through the oscillation of particles in a medium, so it cannot propagate in a vacuum)

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4
Q

The human ear can detect sounds in the frequency range of 2 - 13 MHz

A

F (The human ear detects sounds between 20 Hz and 20 kHz - MHz are in the ultrasound range - far beyond human hearing)

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5
Q

Wavelength is inversely proportional to frequency

A

T

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6
Q

As the frequency of ultrasound increases, the wavelength in soft tissue decreases

A

T (inversely proportional)

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7
Q

The propagation velocity of US is faster in bone than in soft tissue

A

T

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8
Q

Propagation velocity varies depending on the medium

A

T

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9
Q

Acoustic pressure in tissue is unrelated to the energy of the sound wave

A

F (Acoustic pressure is directly related to the energy of the sound wave)

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10
Q

Sound waves require an elastic medium for propagation

A

T

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11
Q

Young’s Modulus measures elasticity, influencing how well sound propagates through the medium.

A

T

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12
Q

Acoustic Impedance (Z) is a measure of how ‘easy’ it is for sound to pass through a medium

A

T

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13
Q

A larger difference in acoustic impedance between two media leads to less reflection of sound waves

A

F (Larger differences in acoustic impedance cause stronger reflections at boundaries)

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14
Q

Big differences in acoustic impedance at an interphase will result in strong reflection of the sound wave

A

T

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15
Q

Impedances should be matched to allow for passage of sound waves through different mediums

A

T

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16
Q

Typical ultrasound absorption in tissue is approximately 10 dB per cm per MHz.

A

F (Typical ultrasound absorption in tissue is approximately 1 dB per cm per MHz.)

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17
Q

Refraction occurs when ultrasound travels between two media with the same propagation velocity.

A

F (Refraction occurs when there is a change in propagation velocity, causing the beam to bend.)

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18
Q

Refraction causes significant artefact

A

F

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19
Q

Diffraction is the bending of the ultrasound beam into the shadow of a strong absorber

A

T

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20
Q

Images in ultrasound are constructed based on the time it takes for the beam to return from a reflecting surface

A

T

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21
Q

The piezoelectric crystal in the transducer changes shape due to the application of electrical voltage.

A

T

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22
Q

The thickness of the transducer crystal is one-quarter of the ultrasound wavelength.

A

F (The thickness of the crystal is half the wavelength of the ultrasound beam.)

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23
Q

The matching layer of a transducer has a thickness of one quarter of the wavelength

A

T

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24
Q

Crystal layer thickness = ? wavelength of US beam
Matching layer thickness = ? wavelength of US beam

A

Crystal layer thickness = ½ wavelength of US beam
Matching layer thickness = ¼ wavelength of US beam

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25
Q

Ultrasound gel is used to prevent air layer reflection and improve contact between the probe and skin.

A

T

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26
Q

An ultrasound pulse contains 5 - 6 wavelengths

A

F (An ultrasound pulse contains 2 - 3 wavelengths

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27
Q

Pulse Duration (PD) is usually approx 1 microsecond

A

T

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28
Q

Increasing SPL, degrades spatial resolution

A

T

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29
Q

The higher the frequency, the shorter the SPL

A

T

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30
Q

Spatial resolution is heavily dependent on SPL

A

T

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31
Q

Shorter SPL results in improved spatial resolution

A

T

32
Q

Longer SPL results in improved spatial resolution

A

F (Shorter SPL results in improved spatial resolution)

33
Q

PRF determines the depth of tissue that we can interrogate

A

T

34
Q

Increasing Pulse Repetition Frequency (PRF) decreases the depth of tissue that can be interrogated

A

T (Less time for echoes to return)

35
Q

The thicker the tissue, the higher the PRF

A

F (The thicker the tissue, the lower the PRF eg. abdomen)

36
Q

Max PRF = c / 2d

A

T

37
Q

Increasing the SPL, decreases the bandwidth

A

T

38
Q

In Doppler Imaging, a shorter SPL is used

A

F (In Doppler Imaging, a longer SPL is used)

39
Q

In conventional U/S imaging, a shorter SPL and wider bandwidth is used

A

T

40
Q

Bandwidth is obtained using Fourier analysis

A

T

41
Q

Only lateral resolution is influenced by bandwidth

A

F (Both axial and lateral resolution are influenced by bandwidth.)

42
Q

Axial spatial resolution is independent of the spatial pulse length

A

F (Axial resolution is directly related to SPL; shorter SPL improves axial resolution.)

43
Q

Shorter SPL improves spatial resolution by allowing close objects to appear as separate structures.

A

T

44
Q

Specular reflection occurs when the boundary between two structures is smooth

A

T

45
Q

Mirror artefacts occur when sound waves reflect off multiple surfaces before returning to the transducer.

A

T

46
Q

Lateral resolution depends on the focusing ability of the transducer and the aperture size.

A

T

47
Q

Near Field = ? Zone
Far Field = ? Zone

A

Near Field = Fresnel Zone
Far Field = Fraunhofer Zone

48
Q

The length of the near field is independent of the aperture

A

F (The length of the near field is dependent on the aperture)

49
Q

The wider the aperture, the longer the near field, and vice verda.

A

T

50
Q

Axial resolution is better than lateral resolution in ultrasound imaging

A

T

51
Q

Axial resolution benefits from longer SPL, making it superior to lateral resolution.

A

F (Axial resolution benefits from shorter SPL, making it superior to lateral resolution.)

52
Q

Time Gain Control (TGC) compensates for tissue attenuation with depth by amplifying echoes based on their time delay

A

T

53
Q

Doppler techniques measure changes in sound velocity caused by moving blood cells.

A

F (Doppler measures changes in frequency, not velocity, to detect motion.)

54
Q

Pulse Wave Doppler allows the analysis of echoes received from specific tissue depths.

A

T

55
Q

The doppler shift can be used to determine the velocity of the flowing blood

A

T

56
Q

The maximum doppler frequency shift that can be detected is determined by the SPL

A

F. (The maximum doppler frequency shift that can be detected is determined by the PRF)

57
Q

The maximum doppler frequency shift that can be detected is determined by the PRF

A

T

58
Q

Increasing PRF will increase the maximum doppler shift

A

T

59
Q

Max doppler shift = PRF/2

A

T

60
Q

Tissue Harmonic Imaging uses nonlinear propagation to generate harmonics for better image quality.

A

T

61
Q

The velocity of sound in soft tissue is approximately 4080 m/s.

A

F (The velocity of sound in soft tissue is approximately 1500 m/s, while it is 4080 m/s in bone.)

62
Q

A larger acoustic impedance mismatch between media leads to stronger sound transmission.

A

F (A larger impedance mismatch results in stronger reflection, not transmission.)

63
Q

Ultrasound waves can experience absorption, reflection, refraction, and diffraction, similar to light waves.

A

T

64
Q

The backing block in a transducer prevents backward transmission of ultrasound waves.

A

T

65
Q

The matching layer between the transducer and the skin is half the wavelength in thickness.

A

F (The matching layer is one-quarter of the wavelength in thickness to optimize transmission.)

66
Q

The spatial resolution of an ultrasound image degrades with depth due to increased SPL

A

T

67
Q

Dispersion refers to the filtering out of higher frequencies in ultrasound imaging.

A

T

68
Q

Lateral resolution depends on the width of the transducer’s beam

A

T

69
Q

Higher PRF results in greater tissue depth interrogation.

A

F (Higher PRF reduces the time for echoes to return, limiting the depth that can be interrogated.)

70
Q

The Doppler shift is proportional to the velocity of the blood flow

A

T

71
Q

The maximum detectable Doppler shift is limited by PRF.

A

T

72
Q

Scattering occurs when ultrasound encounters structures smaller than its wavelength.

A

T

73
Q

Axial resolution improves as the spatial pulse length increases.

A

F (Axial resolution improves with shorter SPL)

74
Q

Time Gain Control (TGC) ensures uniform brightness across all tissue depths.

A

T

75
Q

The aperture size does not affect the focal plane or near field.

A

F (Aperture size influences the focal plane and near field depth, impacting lateral resolution.)

76
Q

The far field (Fraunhofer zone) provides the best lateral resolution for imaging

A

F (Lateral resolution is best in the near field (Fresnel zone), where the beam is more focused.)

RA6007 (5 decks)

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