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Ultrasound Physics > 3 Pulsed Sound > Flashcards

3 Pulsed Sound Flashcards

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0
Q

What are the 2 components of pulsed ultrasound?

A

The CYCLES or “on” or “transmit” time and

The DEAD TIME or “off” or “receive” time.

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1
Q

What is a pulse?

A

A collection of cycles that travel together and must have a beginning and an end.

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2
Q

What are the 5 parameters that describe pulsed sound?

A 
Pulse duration
Pulse repetition period
PRF
Duty factor
Spatial pulse length
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3
Q

What is pulse duration?

A

The time from the start of a pulse to the end of hyphae pulse, ie the actual time that the pulse is “on”.
Typical values: 0.5-3 microsec
Determined by sound source
NOT changed by sonographer

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4
Q

What is the equation for pulse duration?

A

Pulse duration (microsec) = # cycles in pulse x period (microsec)

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6
Q

What type of pulses are used in diagnostic imaging?

A

Short pulses of acoustic energy

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7
Q

What is a pulse?

A

A collection of cycles that travel together

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8
Q

What must a pulse contain?

A

A beginning and an end

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9
Q

What are 2 compartments of pulsed ultrasound?

A
  1. The cycles

2. The dead time

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10
Q

What are 5 additional parameters that describe pulsed sound?

A 
Pulse Duration
Pulse Repetition Period
PRF
Duty Factor
Spatial Pulse Length
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11
Q

What is pulse duration?

A

Time from the start of a pulse to the end of that pulse, the actual time that the pulse is “on”.

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12
Q

What are the units of pulse duration?

A

Microsec (or any unit of time)

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13
Q

What determines pulse duration?

A

Sound source

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14
Q

What are typical values of pulse duration?

A

0.5 - 3 microsec

2-4 cycles

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15
Q

What is the equation for pulse duration?

A

Pulse duration (us) = # cycles in pulse x period (us)

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16
Q

What is the spatial pulse length?

A

Length or distance that an entire pulse occupies in space

17
Q

What are units of spatial pulse length?

A

mm

18
Q

What determines spatial pulse length?

A

Both source and medium

19
Q

Can spatial pulse length be changed by the sonographer?

A

NO

20
Q

What is the equation for spatial pulse length?

A

Spatial pulse length (mm) = # of cycles x wavelength (mm)

21
Q

What is the pulse repetition period?

A

Time from the start of one pulse to the start of the next pulse
Includes 1 pulse duration and 1 “listening time”

22
Q

What are units of the pulse repetition period?

A

msec

23
Q

What is pulse repetition period determined by?

A

Sound source

Imaging depth

24
Q

Can pulse repetition period be changed by sonographer?

A

YES

25
Q

What is PRF (pulse repetition frequency)?

A

Number of pulses created by the system in one second

26
Q

What are the units of PRF?

A

Hertz

27
Q

What is PRF determined by?

A

Sound source

28
Q

Can PRF be changed by the sonographer?

A

YES

29
Q

What is the relationship between pulse repetition period and PRF?

A

Reciprocals

30
Q

What is duty factor?

A

Percentage or fraction of time that the system transmits sound

31
Q

What is duty factor determined by?

A

Sound source

32
Q

Can duty factor be changed by the sonographer?

A

YES

When imaging depth is changed

33
Q

What must an imaging system use?

A

Pulsed ultrasound

34
Q

Describe PRF, duty factor and PRP for both shallow and deep imaging.

A

Shallow imaging: High PRF, High duty factor, Short PRP

Deep imaging: Low PRF, Low duty factor, Long PRP

35
Q

Which parameters describe both pulsed and continuous waves?

A

Period
Frequency
Wavelength
Propagation speed

36
Q

What does the operator change when adjusting the imaging depth?

A

Pulse repetition period
PRF
Duty factor

37
Q

What are characteristics of the pulse itself?

A

Pulse duration

Spatial pulse length

Ultrasound Physics (20 decks)

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