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Echo Physics Midterm Study Guide > Chpts 1-7 > Flashcards

Chpts 1-7 Flashcards

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1
Q

All of the following are acoustic parameters EXCEPT : -Density -Period -Frequency -Propagation Speed

A

Density

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2
Q

Which units are used to report the pressure in the sound beam? - cm - cm/s - pascal - watt

A

pascal

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3
Q

How much bigger is a kilometer bigger than a meter?

A

1000 times

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4
Q

How many hertz are there in 2 MHz?

A

2 millions

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5
Q

Which of the following is an appropriate unit of length (distance)? - second - meter/second - cm - pascal

A

cm

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6
Q

All of the following are acoustic variables EXCEPT : - Pressure - Power - Density - Distance

A

Power

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7
Q

The unit that is used to describe density is :

A

Kg/cm3

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8
Q

All of the following are true of sound waves EXCEPT : - They are pressure waves - They are transverse - They move energy - They are acoustic

A

They are transverse

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9
Q

Which types of waves will exhibit both constructive and destructive interference?

A

Waves of different frequency

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10
Q

Which of the following waves are exhibiting constructive interference?

A

B and C

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11
Q

The typical values of frequency in diagnostic ultrasound is:

A

2 - 15 MHz

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12
Q

Which of the following two parameters are NOT related?

  • Frequency and Period
  • Power and Amplitude
  • Intensity and Power
  • Period and Power
A

Period and Power

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13
Q

Which of the following parameters are determined by both sound source and medium?

  • Frequency
  • Period
  • Power
  • Wavelength
A

Wavelength

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14
Q

If period is 0.5 microseconds, Frequency is :

A

2 MHz

(remember: period and frequency are inversely related to each other. They are reciprocal, meaning when they are multiplied together, the result is 1)

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15
Q

If the wavelength is 4 mm (in soft tissue) , frequency is :

A
  1. 38 MHz
    remember: wavelength (mm) = 1.54 mm/us

frequency (MHz)

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16
Q

The relationship between power and amplitude can be described as :

A

Power is directly related to amplitude2

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17
Q

The only parameter that is determined by the medium is :

A

Propagation Speed

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18
Q

If the amplitude is halved, the intensity will be :

A

Quartered

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19
Q

All of the following are true regarding the 3 bigness EXCEPT :

  • They are determined by the sound source only
  • They are adjustable (initially)
  • They are directly related to propagation speed
  • Watt is the unit of power
A

They are directly related to propagation speed

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20
Q

Propagation speed :

A

Directly related to stiffness and inversely related to density

↑ Stiffness = ↑ Speed

↑ Density = ↓ Speed

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21
Q

Duty factor for continuous-wave is :

A

100 %

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22
Q

What is the wavelength of 1 MHz sound in soft tissue?

A

1.54 mm

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23
Q

What is the speed of sound in soft tissue?

A

1,540 m/s or 1.54 mm/us

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24
Q

Why is wavelength important in diagnostic ultrasound?

A

Short wave = high frequency = better picture

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25
Q

What characteristics of a medium determine the speed of sound in that medium?

A

Density & Stiffness

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26
Q

What other terms describe stiffness?

A

Elasticity & Compressibility

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27
Q

What is a pulsed sound?

A

A collection of cycles that travel together.

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28
Q

Which type of pulse is more desirable in diagnostic imaging, and why?

A

Shorter pulse durations.

They create images of greater accuracy.

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29
Q

What is depth of view?

A

The maximum distance into the body that an ultrasound system is imaging. (Controlled by the sonographer.)

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30
Q

How are pulse repetition period and depth of view related?

A

Directly related.

↑ Depth = ↑ PRP

Depth (mm) ȣ PRP (us)

PRF (MHz)

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31
Q

How are PRF (transmit time) and depth of view related?

A

Inversely related.

↑ Depth = ↓ PRF

The deeper (increase) the depth, the fewer (decrease) pulses transmit into the body.

Depth (mm) ȣ PRP (us)

PRF (MHz)

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32
Q

How is Duty Factor calculated?

A

Duty Factor (%) = Pulse Duration (us) x 100

PRP (us)

33
Q

How does the sonographer change duty factor?

A

By changing the image depth.

34
Q

Of the 4 temporal (time-related) intensity measurements, which has the highest value?

A

Temporal Peak

35
Q

Rank the 5 intensities from largest to smallest.

A
  1. SPTP 2. Im 3. SPPA 4. SPTA 5. SATA
36
Q

The unit of intensity is :

A

Watt/cm2

37
Q

…. is the most relevant intensity with respect to tissue heating.

A

SPTA

38
Q

…. has the lowest value.

A

SATA

39
Q

….. has the highest value.

A

SPTP

40
Q

Beam uniformity coefficient is also called :

A

SP/SA

41
Q

It describes the relationship between the beam intensities with time.

A

Duty Factor

42
Q

Which of the following is unitless and the typical value is 1 or greater?

  • SPTP
  • Duty Factor
  • SP/SA
  • I m
A

SP/SA

43
Q

In pulsed-wave ultrasound, SPTA=SATA, and SATA=SAPA

A

False

44
Q

Temporal average intensity is the average during pulse duration.

A

False

45
Q

What is the meaning of 6 dB change?

A

4 times bigger

46
Q

A wave intensity is 8 mW/cm2 . There is a change of -9dB. What is the final intensity?

A

1 mW/cm2

[when a dB is -3, it is halved. In this question, the intensity will be halved 3 times (-3 ,-3, -3 = -9 dB). So half of 8 is 4, half of 4 is 2, and half of 2 is 1.]

3 dB = double

10 dB = ten times larger

  • 3 dB = half
  • 10 dB = one-tenth
47
Q

Attenuation is …..

A

Directly related to path length and frequency

48
Q

The process that is the most sizable component of attenuation is :

A

Absorption

49
Q

If frequency was 2 MHz, and then becomes 4 MHz, Rayleigh scattering will …..

A

increase by 16 times

(Rayleigh scattering ȣ frequency4)

[When frequency doubles, Rayleigh scattering is 16 times greater (2 x 2 x 2 x 2 = 16)]

50
Q

Rayleigh scattering occurs when the structure’s dimensions are …..

A

much smaller than the beam’s wavelengths

51
Q

In soft tissue, if the frequency is 4 MHz at 10 cm depth, calculate the total attenuation.

A

20 dB

Total attenuation (dB) = attenuation coefficient (dB/cm) x distance (cm)

attenuation coefficient (dB/cm) = frequency (MHz)

2

52
Q

Sound travels in a medium and strikes a boundary with normal incidence. If 60% of the wave’s intensity is reflected, what is the intensity transmission coefficient?

A

40%

53
Q

If the incident intensity is 10 mW/cm2, the reflected intensity is 1 mW/cm2, what is the transmitted intensity?

A

9 mW/cm2

54
Q

Two conditions must be met for refraction to occur, what are they?

A

Oblique incidence and different propagation speeds

55
Q

What are the 3 processes that contribute to attenuation?

A
  1. Reflection
  2. Scattering
  3. Absorption
56
Q

What are the 2 types of reflection?

A
  1. Specular
  2. Diffuse (backscatter)
57
Q

Rayleigh scattering increases dramatically with increasing frequency.

A

True

Rayleigh scattering ȣ Frequency 4

58
Q

Distance and attenuation are related how?

A

Directly.

↑ Distance = ↑ Attenuation

59
Q

Frequency and attenuation are related how?

A

Directly.

↑ Frequency = ↑ Attenuation

60
Q

Absorption is related to frequency how?

A

Directly.

↑ Frequency = ↑ Absorption

61
Q

What are the 3 types of intensities?

A
  1. Incident Intensity
  2. Reflected Intensity
  3. Transmitted Intensity

*All intensities have units of W/cm2.

Incident (starting) Int. =

Reflected Int. + Transmitted Int.

62
Q

Acoustic impedance = ___ x ___.

A

impedance = density (kg/m3) x propagation speed (m/s)

63
Q

What is the percentage of the intensity that bounces back when a sound beam strikes the boundary between 2 media?

A

IRC

Intensity Reflection Coefficient

64
Q

What is the percentage of intensity that passes in the forward direction when the beam strikes an interface between 2 media?

A

ITC

Intensity Transmission Coefficient

65
Q

In clinical imaging, what percentage of a sound wave’s intensity is transmitted at a boundary between 2 soft tissues?

A

99% or more.

66
Q

IRC (%) + ITC (%) = ?

A

100%

67
Q

The percentage of the incident beam that is reflected is related to what?

A

The difference in the impedances of the tissues.

68
Q

With normal incidence, what formula do you use to calculate the IRC?

A
69
Q

The value of the ITC ranges from 0% to 100% and is defined by what formula?

A

ITC (%) = Transmitted Int. x 100

Incident Int.

OR

ITC (%) = 1 - IRC

70
Q

The angle between the incident sound beam and an imaginary line that is perpendicular to the boundary is called what?

A

Angle of Incidence.

71
Q

The angle between the reflected sound beam and the line perpendicular to the boundary is called what?

A

Angle of Reflection.

72
Q

Transmission with a bend is called what?

A

Refraction

73
Q

How do we identify Medium 1 and Medium 2?

A

Medium 1 is the medium in which the sound is currently traveling.

Medium 2 is the medium into which the sound is entering.

74
Q

Under what conditions will the transmission angle be greater than the incident angle?

A

When the speed of Medium 2 is GREATER than the speed of Medium.

The transmission angle will be less than the incident angle when the speed of Medium 2 is LESS than the speed of Medium 1.

75
Q

The maximum imaging depth (depth of view) during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 20 cm. What happens to pulse repetition period (PRP)?

A

PRP is directly related to imaging depth. When imaging depth doubles, PRP doubles.

76
Q

The maximum imaging depth during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 20 cm. What happens to pulse repetition frequency (PRF)?

A

PRF is inversely related to imaging depth. When imaging depth doubles, PRF is halved.

77
Q

A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The maximum imaging depth is 7.7 cm. What is the PRF?

A

77,000 / 7.7 = 10,000 Hz

PRF (Hz) =

77,000 cm/s

imaging depth (cm)

78
Q

What is the formula for Pulse Repetition Period (PRP)?

A

PRP (us) =

imaging depth (cm) x 13 us/cm

ex: When the depth of view is set to 10 cm, PRP is 130 us (10 x 13 us)

79
Q

What term is used to describe the effects of an ultrasound wave on living tissue?

A

Biological effects

Echo Physics Midterm Study Guide (1 decks)

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