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DMS 120 & 122- PHYSICS & HEMODYNAMICS MIDTERM > DMS 120 - PHYSICS MIDTERM > Flashcards

DMS 120 - PHYSICS MIDTERM Flashcards

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1
Q

Interfaces that scatter ultrasound energy are usually considered to be…

A

those that are equal to or smaller than the wavelength.

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2
Q

Regions of lower pressure and density are called…

A

RAREFACTIONS

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3
Q

If you switch to a lower frequency for penetration, the wavelength of the transducer will…

A

increase

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4
Q

The attenuation of a 5.0-MHz transducer at a depth of 4 cm is ____ dB.

A

10.0 dB

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5
Q

The higher the transducer frequency, the higher the…

A

Rayleigh Scattering

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6
Q

The following are all ultrasound frequencies except:

A

15.0 kHz

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7
Q

The duty factor will increase with all of the following :

A
  • pulse repetition frequency.
  • pulse duration.
  • period.
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8
Q

The attenuation of a 5-MHz transducer in soft tissue would be…

A

5.0 dB at 2 cm of depth

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9
Q

What is the period of a 5.0-MHz transducer in soft tissue?

A

0.2 µs

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10
Q

Impedance is equal to density multiplied by:

A

propagation speed

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11
Q

Continuous wave Doppler has a duty factor of ____ %.

A

100

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12
Q

For perpendicular incidence, the incidence angle is ___ degrees.

A

90

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13
Q

Attenuation decreases with an increase in:

A

wavelength

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14
Q

The average propagation speed in human soft tissue is ____.

A

1.54 mm/µs

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15
Q

Frequency is _____ proportional to wavelength.

A

inversely

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16
Q

The distance to a reflector in soft tissue is 15 cm. What is the round-trip time to this depth?

A

195.0 µs

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17
Q

Period is the ____ it takes for one ____ to occur.

A

time; cycle

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18
Q

In oblique incidence the sound is refracted at a boundary between ____ where propagation speeds are different.

A

two media

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19
Q

The propagation speed in soft tissue is not:

A

1.54 m/s.

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20
Q

____ Law relates the transmitted beam direction to the incident beam direction and the speeds of sound in the two materials forming the interface.

A

Snell’s

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21
Q

The pulse repetition frequency is the number of pulses that occur in a ____.

A

second

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22
Q

When frequency increases, the period…

A

decreases.

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23
Q

Amplitude is the maximum variation that occurs in an acoustic ____.

A

variable

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24
Q

3 dB of attenuation means?

A

One half the original intensity.

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25
Q

If beam power increases, intensity will…

A

increase

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26
Q

Propagation speed is the speed at which a wave:

A

travels through a medium.

27
Q

Sound is a ____ longitudinal wave.

A

mechanical

28
Q

The wavelength of 3-MHz ultrasound in soft tissue is ____

A

0.51 mm

29
Q

CW sound is NOT described by:

A

pulse duration

30
Q

____ is the number of complete cycles per second.

A

Frequency

31
Q

As sound travels, the reduction in amplitude and intensity of the wave is called:

A

attenuation

32
Q

Propagation speed is higher or lower in bone than soft tissue?

A

Higher

33
Q

Sound requires a ___ through which to travel.

A

medium

34
Q

Ultrasound pulses contain a range of frequencies called the ____.

A

bandwidth

35
Q

Duty factor is:

A

unitless.

36
Q

The spatial pulse length will not increase with:

A

frequency

37
Q

The propagation speed for a round-trip time of 39 µs is ____ mm/µs.
A. 1540.0
B. 15.4
C 1.45

A

NONE OF THE ABOVE

38
Q

Cycle, period, and frequency are examples of acoustic ____

A

parameters.

39
Q

The fraction of time that pulsed ultrasound is on is called ____.

A

duty factor

40
Q

Pulse repetition frequency is the ____ of pulses occurring in 1 second.

A

number

41
Q

Attenuation is higher OR lower in bone than in soft tissue?

A

higher

42
Q

Compression is not an _____.

A

acoustic variables

43
Q

The best way to describe the role of ultrasound scattering in diagnostic imaging is:

A

that it allows us to see the tissue interfaces .

44
Q

The distance to the reflector in soft tissue with a round-trip time of 39 µs is:

A

30 mm or 3 cm.

45
Q

If the beam area decreases, the intensity will____.

A

increase

46
Q

The four intensity values from the greatest to the least are:

A

SPTP, SATP, SPTA, SATA.

47
Q

Heat production depends most directly on the ____ intensities.

A

SPTA

48
Q

Pulsed wave ultrasound is not described by the terms such as:

A

frequency, wavelength, and propagation speed

49
Q

The rate at which energy passes through a unit area is called _____.

A

power

50
Q

If the density of medium 2 is 10% greater than that of medium 1 and the propagation speeds are equal, the impedance of medium 2 is ____ for medium 1.

A

20% higher

51
Q

Propagation speed is primarily determined by the ____ of the medium.

A

stiffness

52
Q

The unit for impedance is:

A

rayls

53
Q

In oblique incidence the incidence and reflection angles are always:

A

equal

54
Q

If frequency increases, period will _____.

A

decrease

55
Q

Stiffer media have higher or lower sound speeds?

A

higher

56
Q

Intensity is equal to the power of:

A

a wave divided by the area over which the power is spread.

57
Q

20 kHz is equal to…

A

20,000 Hz.

58
Q

500 Hz is equal to…

A

0.500 kHz.

59
Q

TRUE OR FALSE

Stiffer media have higher sound speeds.

A

TRUE

60
Q

TRUE OR FALSE

The impedances of the media determine how much of the incident sound wave is reflected and transmitted into the second medium.

A

TRUE

61
Q

Attenuation encompasses:

A
  • absorption.
  • scattering.
  • reflection.
62
Q

TRUE OR FALSE

Spatial pulse length is determined by the length of the pulse and the propagation speed.

A

FALSE

63
Q

Impedance increases when ____ increases.

A

Density and propagation speed

64
Q

Pulse duration will not increase with…

A

frequency

DMS 120 & 122- PHYSICS & HEMODYNAMICS MIDTERM (2 decks)

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