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Physics 1 > Test 2 > Flashcards

Test 2 Flashcards

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1
Q

If the intensity of the beam is 20 mW/cm^2

A

3dB

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2
Q

What are three names for normal incidence?

A

Right angle
Orthogonal
Perpendicular

Note: Not 45 degrees

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3
Q

What is the property of a medium that provides a measure of resistance to sound passing through the medium?

A

Acoustic impedance

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4
Q

What causes refraction at a tissue interface?

A

Change in propagation speed

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5
Q

What happens to the intensity if the amplitude is increased by a factor of 3?

A

Intensity is increased by a factor of 9.

Note: amplitude multiplied by itself = the amount of intensity

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6
Q

The intensity of an ultrasound beam is 1000 mW/cm^2. You increase the power by 40 dB. What is the new intensity of the beam?

A

10,000,000 mW/cm^2

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7
Q

With absorption, acoustic energy is converted to:

A

Heat

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8
Q

Acoustic impedance is expressed in which unit?

A

Rayl

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9
Q

What is the amount of transmission expected from a soft tissue / air interface

A

1% or less.

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10
Q

If the intensity transmitted at a boundary 40% what is the intensity reflection coefficient?

A

0.6

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11
Q

What is something that would cause a strong echo at an interface?

A

A great change in impedance

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12
Q

True/False

Lower frequency transducers perform better when using harmonics

A

True

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13
Q

What is the angle at which there is a 100% internal reflection and no transmission?

A

Critical angle

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14
Q

Which interaction is responsible for the internal texture of organs in the ultrasound image?

A

Scattering

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15
Q

What is the best estimate of how much a 8 MHz beam will be reduced if it travels a total of 5 cm in soft tissue?

A

20 dB

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16
Q

Determine the percentage of transmitted power at an interface between the two media if the acoustic impedance of the first medium in 3 MRayls and the acoustic impedance of the second medium is 2 MRayls

A

96%

17
Q

(Typed)

One advantage of using harmonics is that the (blank) resolution is improved.

A

Lateral

18
Q

What is the expected attenuation of a 5 MHz sound beam that has returned from a soft tissue target 6cm away?

A

30 dB

19
Q

True/False:

Frequency and propagation speed are indirectly related

A

False

Note: there is NO relationship between frequency and propagation speed

20
Q

Which of the following has the correct relationship to an increase in stiffness?

A

Increased propagation speed

21
Q

An increase in the frequency from 2MHz to 4MHz will have the greatest effect on which type of interface?

A

Rayleigh scatterer

22
Q

True/False:

Attenuation always results in a decibel loss

A

True

23
Q

How are frequency and attenuation related?

A

Directly related

24
Q

What is the attenuation coefficient of a 6MHz probe traveling 2cm?

A

3 dB/cm

25
Q

What is the half value layer for a 12MHz transducer?

A

0.5 cm

26
Q

You had an initial intensity of 10,000 mW/cm^2. You are scanning with a 4 MHz transducer and the beam had a total path length of 10 cm. What is the final intensity of your beam?

A

100mW/cm^2

27
Q

What term describes the distance between the compression zones?

A

Wavelength

28
Q

What does Snell’s law predict?

A

Beam direction transmitted through an interface

29
Q

With a specular reflector, the angle of reflection equals:

A

Angle incident

30
Q

The angle of incidence is equal to 90 degree. The acoustic impedance of medium one equals four rayls and the propagation speed of medium one equals 1.54 mm/microseconds. The acoustic impedance of medium two equals four rayls and the propagation speed of medium two equals 1.45 mm/microseconds. What is the IRC? (%)

A

0%

31
Q

In DMS, what will happen to the wavelength if the frequency doubles?

A

It will be halved

32
Q

True/False:

Scattering reflectors are angle dependent

A

False

Note: Scattering reflectors (non-specular) are frequency dependent; not angle dependent.

33
Q

Rank the propagation speeds of the following mediums from fastest to slowest:

fast, blood, soft tissue

A

Blood, Soft tissue, Fat

34
Q

True/False:

Tissue harmonics are present at the transducer face and near field so artifacts are reduced in these areas

A

False

35
Q

List all the components that go into beam attenuation. (What are the different things that happen to the beam?) You must list all of them to get credit.

A

Reflection
Refraction
Transmission
Absorption

Physics 1 (5 decks)

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