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SPI > Pulsed Waves > Flashcards

Pulsed Waves Flashcards

1
Q

What is pulsed sound?

A
  • systems create short pulses of sound waves to create images
  • collections of cycles that travel together
  • talking & listening (on & off time)
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2
Q

What are pulsed wave parameters?

A
  • pulse duration
  • pulse repetition period
  • pulse repetition frequency
  • duty factor
  • spatial pulse length
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3
Q

What is pulse duration? Unit? Value range? Controlled by? Adjustable?

A
  • time from start to end of pulse
  • unit: time (microseconds)
  • range: 0.3-2.0 microseconds (2-4 cycles per pulse)
  • controlled by source (transducer)
  • not adjustable
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4
Q

Pulse duration is ______ to the number of cycles in a pulse.

A

directly proportional

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5
Q

Pulse duration is ______ to period.

A

directly proportional

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6
Q

Pulse duration is ______ to frequency.

A

inversely proportional

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7
Q

How is pulse duration calculated?

A

number of cycles x period (microseconds) or
number of cycles / frequency (MHz)

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8
Q

What results in long pulse duration?

A

many cycles or cycles with long periods

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9
Q

What results in short pulse duration?

A

few cycles or cycles with short periods, greater image accuracy

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10
Q

What is spatial pulse length? Unit? Value range? Controlled by? Adjustable?

A
  • length/distance from start to end of pulse
  • units: distance (mm)
  • range: 0.1-1.0 mm
  • controlled by source and medium
  • not adjustable
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11
Q

Spatial pulse length is _____ to the number of cycles in a pulse and wavelength.

A

directly proportional

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12
Q

Spatial pulse length is _____ to frequency.

A

inversely proportional

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13
Q

How do you calculate spatial pulse length?

A

number of cycles x wavelength (mm)

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14
Q

What results in long spatial pulse length?

A

many cycles or cycles with long wavelength

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15
Q

What results in short spatial pulse length?

A

few cycles or cycles with short wavelength, greater image accuracy

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16
Q

What is pulse repetition period? Unit? Value range? Controlled by? Adjustable?

A
  • time from the start of one pulse to start of the next including on/off time
  • unit: time
  • range: 100 microseconds to 1 millisecond
  • controlled by source & imaging depth
  • adjustable
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17
Q

How much longer is PRP than pulse duration?

A

100 to 1000x longer

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18
Q

How does imaging depth affect PRP?

A

shallow imaging = shorter PRP
deeper imaging = longer PRP

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19
Q

PRP is _____ to period.

A

unrelated

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20
Q

What is pulse repetition frequency? Unit? Range? Controlled by? Adjustable?

A
  • number of pulses the system transmits into the body each second
  • unit: frequency (Hz)
  • range: 1000-10,000 Hz
  • controlled by source & imaging depth
  • adjustable
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21
Q

PRF is _____ to frequency.

A

unrelated

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22
Q

PRF is ______ to depth.

A

inversely related

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23
Q

How does deep imaging affect PRF?

A

Lower PRF

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24
Q

How are PRP and PRF related?

A

inversely related
- longer PRP = lower PRF, increased PRP = decreased PRF
- shorter PRP = higher PRF, decreased PRP = increased PRF

25
Q

PRP and PRF have a _____ relationship. What equations are used to calculate them?

A

reciprocal (PRF x PRP = 1)
PRF = 1/PRP
PRP = 1/PRF

26
Q

What is duty factor? Unit? Range? Controlled by? Adjustable?

A
  • percentage of time the system transmits a pulse
  • unit: %
  • range: 0.2-0.5%, listening > talking
  • controlled by source & depth
  • adjustable
27
Q

Duty factor is ______ to depth.

A

inversely related

28
Q

When is duty factor at its maximum?

A

DF is at 100% with continuous wave

29
Q

When is duty factor at its minimum?

A

At 0% when transducer is not in use

30
Q

How is duty factor calculated?

A

pulse duration/PRP x 100

31
Q

What is the result of shallow imaging on PRP, PRF, and duty factor?

A

Shallow imaging = less listening, more talking
- shorter PRP
- higher PRF
- higher duty factor

32
Q

What is the result of deeper imaging on PRP, PRF, and duty factor?

A
  • more listening, less talking
  • longer PRP
  • lower PRF
  • lower duty factor
33
Q

What is intensity? How is it calculated?

A
  • sound beam’s power divided by area
  • watts/cm^2
34
Q

What is spatial intensity?

A
  • distance/space
  • beam does not have same intensity at different locations
35
Q

What is peak intensity?

A

max intensity value

36
Q

What is average intensity?

A

middle intensity value

37
Q

What is temporal intensity?

A
  • all time, pulse duration and receive
  • beam does not have same intensity at different times
38
Q

What is pulsed intensity?

A
  • only transmit time
  • beam does not have same intensity at different times during pulse, average intensity for pulse duration only
39
Q

Intensity of the sound beam varies over ______ and ______.

A

distance and time, important when studying sound beam bioeffects

40
Q

How can spatial intensity be compared to a flashlight?

A
  • beam is strongest centrally, highest intensity
  • dimmer around edges, lower intensity
41
Q

What is Spatial Peak Intensity?

A
  • beam’s intensity at location where it is highest
  • always higher than the average
42
Q

What is Spatial Average Intensity?

A

average intensity across entire cross-sectional area of beam

43
Q

What is Temporal Peak Intensity?

A

intensity of beam at time of max value

44
Q

What is Imax?

A

average intensity during most intense half cycle

45
Q

What is Pulse Average Intensity?

A

average intensity during pulse duration (transmit time)

46
Q

What is Temporal Average Intensity?

A

average intensity during PRP (transmit/receive time)

47
Q

What is I sptp?

A

measurement at location where intensity is at its max & at the instant in time when the most powerful part of the pulse passes

48
Q

What is I sppa?

A

measurement at location where intensity is at its max, averaged over pulse duration (transmit time)

49
Q

What is I spta?

A

measurement at location where intensity is at its max, averaged over all time (PRP)

50
Q

What is I sata?

A

measurement over the entire beam cross-sectional area over all time (PRP)

51
Q

What is the most important intensity in regard to bioeffects?

A

SPTA

52
Q

What is the unit for all intensities?

A

watts/cm^2

53
Q

Which intensity has the highest value? Which has the lowest?

A

Highest: SPTP
Lowest: SATA

54
Q

What is the beam uniformity coefficient? What is it also called?

A

It describes the spread of a beam in space, AKA SP/SA factor, unitless, value of 1 or greater

55
Q

How is duty factor related to intensity?

A

Describes the relationship of beam intensities with time

56
Q

How does continuous wave ultrasound affect intensity?

A

Beam is always on, pulse average intensity = temporal avg intensity
SPTA = SPPA, SATA=SAPA

57
Q

When pulsed and continuous wave sound beams have the same SPTP intensities, which beam has the higher
SPTA intensity?

A

continuous wave

58
Q

When pulsed and continuous wave sound beams have the same SATP intensities, which beam has the higher SATA intensity?

A

continuous wave

59
Q

Rank the following from largest to smallest:
SPTA, Im, SPPA, SATA, SPTP

A

SPTP, Im, SPPA, SPTA, SATA

SPI (9 decks)

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