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Physics 1 > Test 3 > Flashcards

Test 3 Flashcards

1
Q

What is the pulse repetition period if the pulse repetition frequency is 5 kHz?

A

0.2 ms

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2
Q

If the number of cycles in a pulse is increased, but the wavelength remains the same, what else is being increased or decreased?

A

The pulse duration is increased

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3
Q

What is the term for the time from the beginning of one pulse to the beginning of the next pulse?

A

Pulse repetition period

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4
Q

How does increasing the depth effect spatial pulse length?

A

The SPL has no change

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5
Q

How does increasing the depth affect the duty factor?

A

The duty factor decreases

(Inversely related)

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6
Q

How does increasing the depth effect pulse repetition period?

A

The PRP increases

(Directly related)

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7
Q

How does increasing the depth affect the pulse duration?

A

The pulse duration has no change

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8
Q

How does increasing the depth affect the propagation speed?

A

Depth and Propagation speed have NO RELATION.

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9
Q

How does increasing the depth affect the number of cycles?

A

The depth and the number of cycles have NO RELATION.

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10
Q

What is a change that would cause the pulse duration to increase?

A

Frequency decreases

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11
Q

If the pulse repetition period (PRP) is 330 microseconds, what is the pulse repetition frequency?

A

3 kHz

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12
Q

What is the fraction of time the sound is actually on?

A

Duty factor

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13
Q

What is the duty factor?

Given: PD = 1
SPL = 0.5
PRF = 0.2

(Units not given to prevent overlap with another question. You should assume these are all matching units)

A

0.2 or 20%

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14
Q

In diagnostic medical sonography, the beam would reach a reflector of approximately _____________ deep in 20 µs

A

3 cm

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15
Q

In DMS, what is the most common unit for spatial pulse length?

A

mm

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16
Q

What is the unit for Duty factor?

A

Unitless

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17
Q

What is the SPL if the wavelength is 2mm and there are 3 cycles in the pulse?

A

6 mm

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18
Q

PRF is the number of ____________ occurring in 1 second.

A

Pulses

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19
Q

If the pulse repetition frequency decreases, what is something else that happen?

A

The duty factor decreases

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20
Q

Use the information below and solve for PRP

Frequency - 6 MHz
Reflector Depth - 6 cm
Number of Cycles - 2

A

0.15633 ms or 156.33 microseconds

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21
Q

Use the information below and solve for SPL

Frequency - 2 MHz
Reflector Depth - 6 cm
Number of cycles - 2

A

1.54 mm

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22
Q

It took the beam 45.5 µs to reach the reflector. How deep did the beam travel?

A

7 cm

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23
Q

You are scanning with a 4 MHz transducer that has 2 cycles per pulse. You note a mass that is at a distance of 8 cm. What is the pulse repetition frequency for this example?

A

9.57 kHz

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24
Q

What is the relationship of frequency to absorption?

A

If frequency is doubled, absorption is doubled.

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25
Q

True/False

Continuous wave differs in that the probe has only one crystal to send and receive signals and pulse wave probes have two crystals.

A

False

26
Q

What determines the number of cycles in a pulse?

A

Backing layer

27
Q

True/False

A longer spatial pulse length yields better image resolution

A

False

28
Q

What can the sonographer do to obtain the best image of a specular reflector?

A

The sonographer can maneuver their probe perpendicular to the interface

29
Q

What does a duty factor of 1 mean?

A

That the machine is always on.`

30
Q

You are scanning with a 3 MHz transducer that has 2 cycles per pulse. You note a mass that is at a distance of 11 cm. What is the pulse repetition frequency?

Round to two decimal places

A

6.96 kHz

31
Q

The intensity of the beam is 20 mW/cm^2 and you reduce the intensity by one half, what is the decibel loss?

A

3 dB

32
Q

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

A

Amplitude is increased by a factor of 9

33
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

34
Q

With absorption, acoustic energy is converted to:

A

Heat

35
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

36
Q

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

A

30 dB

37
Q

What is something else that happens when stiffness is increased?

A

Propagation speed is increased (directly related)

38
Q

True/False

Attenuation always results in a decibel loss

A

False

39
Q

How are frequency and attenuation related?

A

Directly related

40
Q

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

A

3 dB/cm

41
Q

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

A

0.5 cm

42
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?

A

100 mW/cm^2

43
Q

What term describes the distance between compression zones?

A

Wavelength

44
Q

What term describes the time between compression zones?

A

Period

45
Q

List all the components that go into beam attenuation:

A

Reflection
Refraction
Transmission
Absorption

46
Q

It takes _________ microseconds for ultrasound to travel 1.54 cm in soft tissue.

A

10 microseconds

47
Q

Intensity is the _________ in a wave divided by ___________

A

Intensity = Power divided by Area

48
Q

Intensity is proportional to ___________ squared

A

Intensity is proportional to amplitude squared

49
Q

If power is doubled, and the area remains unchanged, intensity is ___________

A

Halved

50
Q

If amplitude is doubled, intensity is ___________

A

Quadrupled

51
Q

If a sound beam has a power of 10 m/W and a beam area of 2cm^2, the spatial pulse average intensity is ___________ mW/cm^2

A

5

52
Q

Attenuation is the reduction in _____________ and _____________ as a wave travels through a medium.

A

reduction in amplitude & intensity

53
Q

Attenuation consists of ___________, ___________, and _____________ .

A

Absorption, reflection, and scattering.

54
Q

The attenuation coefficient is attenuation per ____________ of sound traveled.

A

Centimeter

55
Q

For soft tissues, there is approximately ___________ dB of attenuation per centimeter for each megahertz of frequency.

A

0.5 dB

56
Q

For soft tissues, the attenuation coefficient at 3 MHz is approximately __________ .

A

1.5 dB/cm

57
Q

The attenuation coefficient in soft tissue ____________ while frequency increases.

A

Increases

58
Q

Absorption is the conversion of __________ to __________.

A

Sound to Heat.

59
Q

The imaging depth (penetration) _____________ while frequency increases.

A

decreases

60
Q

The depth at which half-intensity occurs in soft tissues at 7.5 MHz is _________ .

A

0.8 cm

61
Q

For an incident intensity of 2 mW/cm^2 and impedances of 49 and 51 rayls, the reflected intensity is _________ mW/cm^2 and the transmitted intensity is ______mW/cm^2

A

(0.0008 reflected & 1.9992 transmitted)

Physics 1 (6 decks)

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