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Ultrasound SPI exam > Physical Principles > Flashcards

Physical Principles Flashcards

1
Q

Which of the following factors does NOT affect impedance?

A

frequency

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2
Q

You are imaging a structure containing two media having the same acoustic impedance. What will occur at the boundary of the two structures?

A

All of the sound will be transmitted

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3
Q

The unit of impedance

A

Rayl

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4
Q

An example of a spectacular reflector is

A

Pericardium

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5
Q

What system control can you adjust to compensate for the effect of sound attenuation in the body?

A

TGC

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6
Q

The algebraic summation of waves leading to patterns of minima and maxima is called:

A

Interference

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7
Q

What sound parameter is determined only by the medium?

A

Propagation speed

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8
Q

Snell’s law describes

A

The angle of sound transmission at an interface between media having different propagation speeds

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9
Q

During the performance of a sonogram, you would be most likely to encounter refraction in this view:

A

Curved interface

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10
Q

You may observe sound attenuation by all of the following EXCEPT:

A

Compression

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11
Q

When you image sound reflected from a large, smooth interface, you are observing results of:

A

Specular reflection

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12
Q

Normal incidence (perpendicular incidence) occurs when

A

the sound beam strikes the interface at a 90 degree angle

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13
Q

During a sonographic examination of a large vessel, a 45 degree beam to vessel angle would be called:

A

Oblique incidence

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14
Q

What occurs when you image a structure with oblique incidence?

A

The angle of reflection will be oriented away from the transducer resulting in a decreased visualization of the structure

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15
Q

The shadow depicted in an image of a renal stone is primarily a result of the following sound tissue interaction:

A

Reflection: very little sound is transmitted through the stone to provide reflections from tissue distal to the stone, this results in shadowing distal to the calcification

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16
Q

Which of the following statements regarding the effect of frequency on Rayleigh scattering is TRUE?

A

Scattering intensity is proportional to frequency raised to the fourth power

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17
Q

An echo from which one of the following sound reflector is most dependent on the angle of incidence?

A

Specular reflector, the angle of reflection is equal to the angle of incidence

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18
Q

What determines acoustic impedance?

A

Density and propagation speed of the medium

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19
Q

What system control should you adjust to compensate for sound attenuation with increasing depth?

A

TGC

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20
Q

Diffuse Reflection

A

the reflected beam is scattered in various directions

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21
Q

According to snells law the angle of transmission is related to the incident beam angle and:
amount of acoustic impedance mismatch at interface
change in frequency that occurs at an interface
one half the angle of incidence
the relative speeds of sound in the two media
the percentage of diffraction distal to the interface

A

the relative speeds of sound in the two media
snells law dictates the angle of transmission that will occur at an interface with refraction of the sound beam, Refraction (bending) of the sound beam occurs whenever there is oblique incidence and different propagation speeds between two media

22
Q

which of the following interactions of sound and tissue decreases the intensity of the transmitted beam?
absorption, reflection, scattering, conversion of sound to heat, all the above

A

all of the above

all of these interactions will result in decreased intensity of the transmitted beam

23
Q

The relationship of frequency to absorption

A

if frequency is doubled absorption is doubled

Directly related to one another

24
Q

The reduction in the intensity of sound as it propagates through tissue

A

Attenuation

25
Q

another term for nonspecular reflection

A

Scattering occurs when the interface is small, less than several wavelengths across

26
Q

Frequency and Attenuation are related how?

A

Directly if one is doubled the other is also doubled

27
Q

As frequency increases wavelength

A

decreases improving resolution but decreasing penetration because of increased sound absorption

28
Q

You are scanning a large mass that is composed primarily of fat. Which of the following are most likely to encounter?

A

Axial misregistration of objects distal to the mass on the screen due to the slower propagation speed through fat

29
Q

What two conditions must be present to cause refraction of a sound wave?

A

Oblique incidence and different media propagation speeds

30
Q

The transducer you are using transmits wide bandwith pulses whose frequency content is 2-5MHz which of the following describes the reflected echo signals after they have traversed the tissue?

A

The echo signals will be shifted down in frequency due to the increased attenuation of higher frequencies

31
Q

When the sound beam is refracted during a sonographic examination, which of the following might you detect on the ultrasound image?

A

Lateral misregistration

32
Q

refraction

A

bending of the sound beam that results in lateral misregistration of structures posterior to the refracted beam

33
Q

what can you do to enhance the visibility of a specular reflector?

A

scan with perpendicular incidence

34
Q

What interaction of ultrasound and tissue is primarily responsible for imaging the internal structure of organs?

A

scattering

35
Q

what sound tissue interaction is necessary to form an ultrasound image?

A

reflection

36
Q

For soft tissue, one of the factors responsible for determining acoustic impedance is

A

Density

37
Q

You are imaging a structure that is highly attenuating. Which imaging effect do you expect to encounter?

A

Shadowing

38
Q

What would you change if the image does not show adequate penetration and the far field displays noise instead of tissue?

A

Decrease transmit frequency

39
Q

For pulsed ultrasound, which of the following factors determine the frequency of the sound wave?

A

transmitter frequency

40
Q

The maximum cyclical change in a quantity is known as

A

Amplitude

41
Q

sound propagation in a medium

A

molecules oscillate back and forth to propagate sound waves but do not move from one end of the medium to another
Molecules oscillate back and forth to propagate sound waves but do not move from one end of the medium to another

42
Q

What term denotes the time it takes for one cycle to occur

A

Period

43
Q

if the number of cycles in a pulse is increased but the wavelength remains the same, whats true?

A

The pulse duration is increased (the time it takes to complete one pulse, if the number of cycles in the pulse is increased, it will take more time for one pulse to occur)

44
Q

What is most likely to decrease beam intensity?

A

increasing beam area

For a given output power the intensity is expected to fall if the beam area is increased

45
Q

Regions of low pressure and density that are formed during sound propagation are termed

A

Rarefactions

46
Q

What property would result in increased propagation speed of sound through a medium

A

Increased stiffness

47
Q

attenuation is proportional to

A

frequency

48
Q

What frequencies are best to use for scanning a large patient;s abdomen

A

lower frequencies

49
Q

Velocity of ultrasound wave in bone

A

4080 m/s

50
Q

Wavelength is measured in

A

Millimeters

51
Q

Regions of decreased particle density in a sound beam

A

Rarefaction

52
Q

ultrasound propagation velocity depends on

A

density and compressibility

Ultrasound SPI exam (2 decks)

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