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CMI 350 > Ch.4 Describing Pulsed Waves > Flashcards

Ch.4 Describing Pulsed Waves Flashcards

1
Q

what are the five parameters that describe pulsed sound?

A

Pulse duration
Pulse Repetition Period
Pulse Repetition Frequency
Duty Factor
Spatial Pulse Length

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2
Q

what is a pulse?

A

is a collection of cycles that travel together as a unit

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3
Q

Pulsed Ultrasound has two components

A

transmit, talking, on time
receive, listenting, off time

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4
Q

Each particular ultrasound transducer emits a pulse with a fixed _____

A

duration that can not be changed for that transducer

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5
Q

Pulse duration

A

is the actual time from the start to the end of a pulse
-is a single transmit, talking, or on time

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6
Q

Pulse duration:
Units
Determined by
Typical Values
Adjustable

A

microseconds (us)
sound source ONLY
0.5 to 3.0 us
NOT

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7
Q

Pulse duration formula

A

(us) = # cycles x period (us)

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8
Q

Pulse Duration is:
directly proportional to the ____ of ____
directly proportional to _____
inversely proportional to ______

A

the number of cycles
period
frequency

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9
Q

Describe two characteristics of pulses with a long duration

A

many cycles in the pulse
or individual cycles with long periods

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10
Q

Describe the two characteristics of pulses with a short duration

A

few cycles in the pulse
or individual cycles with short periods

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11
Q

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

A

Shorter duration pulses are better for imaging bc they create images of greater accuracy

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12
Q

Spatial Pulse Length

A

is the distance that a pulse occupies from the start to the end of a pulse

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13
Q

Spatial Pulse Length:
Units
Determined by
Adjustable
Typical Values

A

mm
Both Sound/Medium
No
in soft tissue 0.1 to 1.0 mm

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14
Q

Spatial Pulse Length:
directly proportional to the __ of ____
directly proportional to _____
inversely proportional to _____

A

of cycles
wavelength
frequency

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15
Q

Spatial Pulse Length formula

A

(mm) = # cycles x wavelength (mm)

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16
Q

What are the two characteristics that distinguish long pulse length pulses from short pulse length pulses?

A

Long pulses have
many cycles
longer wavelengths
vs
Short pulses have
fewer cycles
shorter wavelengths

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17
Q

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

A

Pulses of shorter length are desirable bc they create more accurate images

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18
Q

Pulse Repetition Period (PRP)

A

is the time from the start of one pulse to the start of the next pulse (transmit and receive)

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19
Q

PRP:
Units
Determined by
Adjustable
Typical values

A

ms, us
Sound source ONLY
(imaging depth)
YES (Adjust Depth of View)
0.1 to 1.0 ms
(100 to 1000 times longer than pulse duration)

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20
Q

When the system is imaging at shallow depths, the time from one pulse to the next is ______

A

Short

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21
Q

When the system is imaging more deeply, the time from one pulse to the next is ______

A

Longer

22
Q

What is depth of view?

A

describes the maximum distance into the body that an ultrasound system is imaging. Sonographer controls this. The white dots along the edge of the screen indicate depth

23
Q

How are pulse repetition period and depth of view related?

A

directly related

24
Q

What are the two components of pulse repetition period? Which one can the sonographer change?

A

the transmit time (on)
the receive time (off)

Transmit time is called pulse duration which can NOT be changed since its a fixed value of the transducer

25
Q

With deeper imaging, the listening time and the pulse repetition period _____

A

lengthen

26
Q

With shallower imaging, the listening time and the pulse repetition period _______

A

shorten

27
Q

Pulse Repetition Frequency (PRF)

A

is the number of pulses that an ultrasound system transmits into the body each second
(# of cycles are meaningless)

28
Q

PRF:
Units
Determined by
Adjustable
Typical Values

A

Hertz (per second)
Sound Source ONLY
(MAX imaging depth)
YES (adjust depth of view)
1,000 to 10,000 Hertz

29
Q

When the system is imaging shallow, the pulse repetition frequency is ______

A

higher

30
Q

When the system is imaging deep, the pulse repetition frequency is _____

A

lower

31
Q

PRP & PRF are ONLY related to?

A

Depth of view

32
Q

How are PRF and depth of view related?

A

Inversely related

33
Q

How are PRP and PRF related?

A

inversely related and reciprocal (1/PRP)

34
Q

A longer PRP results in a _______ PRF

A

lower

35
Q

A shorter PRP results in ______ PRF

A

higher

36
Q

Duty Factor

A

is the percentage of fraction of time that the system transmits a pulse

37
Q

Duty Factor:
Units
Determined by
Adjustable
Typical Values

A

None
Sound Source ONLY
YES (adjust depth of view)
0.2% to 0.5%

38
Q

Duty Factor is inversely related to _______ _______

A

imaging depth

39
Q

Duty Factor is _____ when the system is imaging at shallow depths, and ______ when imaging at greater depths.

A

higher
lower

40
Q

How is Duty Factor calculated?

A

(%) = (pulse duration / pulse rep. period) x 100

41
Q

What are the maximum values for duty factor?

A

maximum value is 1 or 100%; this value is only achieved with continuous wave sound (must always be less than 100%)

42
Q

What are the minimum values for duty factor?

A

minimum value is 0% which exits only when the transducer is silent
typical: 0.2%
this means the system is listening approx 500 times longer than it is transmitting

43
Q

How does the sonographer change duty factor?

A

changes when the sonographer alters imaging depth

44
Q

As imaging depth increases, transmit time, or pulse duration, _____ _____ while listening time is ___________

A

remains constant
prolonged

45
Q

Duty factor increases with ______ imaging.
Duty factor ______ with deeper imaging.

A

shallower

decreases

46
Q

Duty Factor:
Shallow Imaging
4 Characteristics

A

Less listening
Shorter PRP
Higher PRF
Higher duty factor

47
Q

Duty Factor:
Deep Imaging
4 Characteristics

A

More listening
Longer PRP
Lower PRF
Lower Duty Factor

48
Q

Which of the 5 parameters that describe pulsed sound are determined by the sound source?

A

Pulse Duration
Pulse Repetition Period
Pulse Repetition Frequency
Duty Factor

49
Q

Which of the 5 parameters that describe pulsed sound are determined by BOTH sound and medium?

A

Spatial Pulse Length

50
Q

Which of the 5 parameters that describe pulsed sound can be changed with imaging depth?

A

Pulse Repetition Period
Pulse Repetition Frequency
Duty Factor

51
Q

Which of the 5 parameters that describe pulsed sound can NOT be changed with imaging depth?

A

Pulse duration
Spatial Pulse length

52
Q

What are the 4 parameters that describe a single cycle can describe both pulsed and continuous wave sound?

A

Period
Frequency
Wavelength
Propagation Speed

CMI 350 (11 decks)

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