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*Ultrasound Physics* > Ch. 4 - Pulsed Sound > Flashcards

Ch. 4 - Pulsed Sound Flashcards

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1
Q

In diagnostic imaging, short _____ of _____ _____ are used to create anatomic images.

A

pulses of acoustic energy

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2
Q

T or F? Continuous wave sound can create anatomic images.

A

False

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3
Q

What is the term for a collection of cycles that travel together?

A

pulse

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4
Q

A pulse must have a _____ and a(n) _____, otherwise the sound is a continuous wave.

A

beginning

end

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5
Q

What are the 2 components of pulsed ultrasound?

A 
cycles ("on" or "transmit" time)
dead time ("off" or "receive" time)
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6
Q

What are 5 additional parameters of pulsed sound?

A 
Pulse Duration (PD)
Pulse Repetition Period (PRP)
Pulse Repetition Frequency (PRF)
Duty Factor (DF)
Spatial Pulse Length(SPL)
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7
Q

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

A

Pulse Duration

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8
Q

What is the unit for pulse duration?

A

microsecond (or any unit of time)

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9
Q

Is the pulse duration determined by the sound source or the medium?

A

sound source

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10
Q

Pulse duration is determined by multiplying the number of _____ in the pulse and the _____ of each cycle.

A

cycles

period

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11
Q

Can the pulse duration be changed by the sonographer?

A

No (it is characteristic of each transducer, it does not change when altering the image depth)

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12
Q

The typical values of Pulse Duration are

A

0.5 - 3 microseconds

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13
Q

A Pulse is comprised of how many cycles?

A

2 - 4 cycles

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14
Q

The equation for Pulse Duration is

A

cycles in pulse
X period
————————-
Pulse Duration

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15
Q

The length or distance that an entire pulse occupies in space. The distance from the start to the end of one pulse.

A

Spatial Pulse Length

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16
Q

The unit for Spatial Pulse Length is

A

mm (or any unit of distance)

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17
Q

Can Spatial Pulse Length be changed by the sonographer?

A

No

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18
Q

The typical values of Spatial Pulse Length are

A

0.1 - 1mm

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19
Q

Spatial Pulse Length determines _____ _____.

A

axial resolution (image quality)

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20
Q

Shorter pulses create _____ (lower/higher) image quality.

A

higher

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21
Q

The equation for Spatial Pulse Length is

A 
# of cycles
  X wavelength (mm)
-----------------------------
Spatial Pulse Length
(mm)
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22
Q

The time from the start of one pulse to the start of the next pulse. It includes one pulse duration and one “listening time”.

A

Pulse Repetition Period

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23
Q

The units for Pulse Repetition Period are

A

microseconds (or any unit of time)

24
Q

The Pulse Repetition Period is determined by the

A

sound source

25
Q

Can the Pulse Repetition Period be changed by the sonographer?

A

Yes (when adjusting the depth of view, this changes the “listening time”)

26
Q

Typical values for Pulse Repetition Period are

A

100 microseconds to - 1 ms

27
Q

In reality, the _____ time is hundreds of times longer than the _____ time (pulse duration).

A

listening

talking

28
Q

As imaging depth increases, PR Period _____ (increases/decreases).

A

increases

29
Q

As imaging depth decreases, PR Period _____ (increases/decreases).

A

decreases

30
Q

_____ is the number of pulses that occur in 1 second.

A

Pulse Repetition Frequency

31
Q

Units for Pulse Repetition Frequency are

A

Hertz (Hz)

32
Q

Pulse Repetition Frequency is determind by the

A

sound source

33
Q

Can the Pulse Repetition Frequency be changed by the sonographer?

A

Yes

34
Q

The typical values for Pulse Repetition Frequency are

A

1,000 - 10,000 Hz (1-10 kHz)

35
Q

T or F? The Pulse Repetition Frequency is determined by the imaging depth.

A

True

36
Q

As imaging depth increases, Pulse Repetition Frequency _____ (increases/decreases).

A

decreases

37
Q

Imaging depth and Pulse Repetition Frequency have a(n) _____ (inverse/direct) relationship.

A

inverse

38
Q

Since the depth of view is changed by the sonographer, the sonographer changes the Pulse Repetition Frequency. The operator actually adjusts the _____ _____ ____, thereby changing the Pulse Repetition Frequency.

A

pulse repetition period

39
Q

Pulse Repetition Period and PRF are _____ (relationship).

A

Reciprocals

40
Q

Since Pulse Repetition Period and PRF are reciprocals, the Pulse Repetition Period also depends on _____ _____ (since Pulse Repetition Frequency does too).

A

imaging depth

41
Q

The equation for Pulse Repetition Frequency is

A

Pulse Repetition Period
X Pulse Repetition Frequency (Hz)
————————————————–
1

42
Q

Pulse Repetition Frequency is determined only by imaging depth. Pulse Repetition Frequency _____ (is/is not) related to frequency.

A

is not

43
Q

The percentage or fraction of time that the system transmits sound is

A

Duty Factor

44
Q

The units for Duty Factor are

A

NONE (unitless)

Max = 1 or 100%, continuous wave
Min = 0 or 0%, the system is off
45
Q

Duty Factor is determined by the

A

sound source

46
Q

Can Duty Factor be changed by the sonographer?

A

Yes

47
Q

The typical values for Duty Factor are

A

from 0.1% to 1% or 0.001 to 0.01

little talking, lots of listening

48
Q

T or F? Duty Factor always has a small value.

A

True

49
Q

With Duty Factor, with deeper imaging, the Duty Factor is _____ (smaller/bigger).

A

smaller

50
Q

Shallow imaging has the same meaning as

A

deep imaging

51
Q

High Pulse Repetition Frequency (PRF) has the same meaning as

A

Low Pulse Repetition Frequency (PRF)

52
Q

High Duty Factor has the same meaning as

A

Low Duty Factor

53
Q

Short Pulse Repetition Period has the same meaning as

A

Long Pulse Repetition Period

54
Q

By adjusting the imaging depth, the operator changes these 3 things as well

A

Pulse Repetition Period
PRF
Duty Factor

55
Q

Parameters for sound describe the

A

features of sound

56
Q

Typical Duty Factor for anatomical imaging is

A

0.2%

57
Q

Listening Time is usually ____ times longer than ____ Time in anatomical imaging.

A

500

Talking Time

*Ultrasound Physics* (5 decks)

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