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Chapter 4 Flashcards

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1
Q

Can continuous wave ultrasound create anatomic images?

A

No

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2
Q

Short bursts of sound called _ are used in diagnostic ultrasound

A

Pulses

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3
Q

A pulse of ultrasound is a _

A

collection of cycles that travel together

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4
Q

Pulsed ultrasound is made up of _

A

individual cycles that travel together as a unit

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5
Q

Pulsed Ultrasound is made up of two components:

A

Transmit time (talking) Receive time (listening)

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6
Q

Five Parameters for Pulsed Ultrasound

A

Pulse duration
Pulse repetition period Pulse repetition frequency Duty factor
Spatial pulse length

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7
Q

The actual time from the start of a pulse to the end of that pulse

A

Pulse duration

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8
Q

Units for pulse duration

A

units of time, microsecond

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9
Q

Typical value for pulse duration

A

0.3 to 2.0 microseconds

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10
Q

In clinical imaging, a pulse is comprised of _ cycles

A

2-4

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11
Q

Pulse duration is determined by

A

sound source only

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12
Q

Is pulse duration adjustable by the sonographer

A

No

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13
Q

_ is a characteristic of each transducer. Does not change with imaging depth.

A

Pulse duration

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14
Q

Pulse duration (μs) =

A

of cycles x period

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15
Q

Relationship between pulse duration and the number of cycles in the pulse

A

Directly proportional

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16
Q

Relationship between pulse duration and period

A

Directly proportional

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17
Q

Relationship between pulse duration and frequency

A

Inverse

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18
Q

Pulse duration =

A

cycles/frequency

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19
Q

Pulses of long duration have _ cycles in the pulse or _

A

Many

individual cycles with long periods

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20
Q

Pulses of short duration have _ cycles in the pulse or _

A

Few

individual cycles with short periods

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21
Q

Pulses with _ duration are desirable for imaging because _

A

Shorter

they create images of greater quality and accuracy.

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22
Q

The distance that a pulse occupies in space from the start to the end of a pulse.

A

Spatial Pulse Length

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23
Q

Units for spatial pulse length

A

Distance such as mm

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24
Q

Typical values for spatial length

A

in clinical imaging, SPL in

soft tissue ranges from 0.1 to 1 mm

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25
Spatial pulse length is determined by
both the sound source and the medium.
26
SPL =
of cycles in pulse x the wavelength of each cycle
27
Is spatial pulse length adjustable by the sonographer
No
28
Since _ is determined by both the source and the medium, so is SPL
Wavelength
29
Spatial pulse length (mm) =
cycles x wavelength (mm)
30
Relationship between spatial pulse length and the number of cycles in the pulse
Directly proportional
31
Relationship between spatial pulse length and wavelength
Directly proportional
32
Relationship between spatial pulse length and frequency
Inverse
33
Spatial Pulse Length is the _ of the pulse from _
distance end to end ◆millimeters
34
Pulse duration is the _ that a pulse is “on”
Time Microseconds
35
Two characteristics create long pulses:
Many cycles in the pulse | Cycles with longer wavelengths
36
Two characteristics create short pulses:
Fewer cycles in the pulse | Cycles with shorter wavelengths
37
Pulses of shorter length are desirable because they create
more accurate images and improve resolution
38
The “on” or talking time of a single pulse
Pulse duration
39
_ the time from the start of one pulse to the start of the next pulse. It includes one pulse duration plus one listening time.
Pulse repetition period
40
Unit for pulse repetition period
Time such as milliseconds
41
Typical values of PRP
In diagnostic ultrasound, 100 | microseconds to 1 millisecond
42
PRP is generally _ than pulse duration
100-1,000 times longer
43
PRP is determined by
Sound source only
44
Can PRP be adjusted by sonographer
Yes, by changing the image depth
45
_ describes the maximum distance into the body that an ultrasound system is imaging
Depth of view
46
The markers along the edge of an image indicate
Depth
47
Relationship between PRP and depth
Directly related
48
When the system is imaging more deeply, the time from one pulse to the next is _. Therefore PRP _
Longer | Increases
49
When the system is imaging at shallow depths, the time from one pulse to the next is _. Therefore PRP _
Shorter Decreases
50
_ changes listening time
Depth
51
The two components of PRP are
Transmit time or “on” time (Pulse duration) and | Receive time or “off” time
52
the number of pulses that an ultrasound system transmits into the body each second.
Pulse repetition frequency
53
Units for PRF
Hertz
54
Typical values for PRF
1,000 to 10,000 Hz (pulses per second) We commonly use KHz
55
PRF is determined by
Sound source only
56
Can PRF be adjusted by sonographer
Yes, by adjusting image depth
57
Is PRF related to frequency
No
58
Relationship between PRF and depth
Inverse
59
Shallow imaging= _ PRF
High
60
Deeper imaging= _ PRF
Lower
61
Relationship between PRP and PRF
Inverse and reciprocal
62
A longer PRP results in a _ PRF
Lower
63
A shorter PRP results in a _ PRF
Higher
64
PRF=
1/PRP
65
PRP=
1/PRF
66
PRF X PRP=
1
67
the percentage or fraction of time that the system transmits a pulse.
Duty factor
68
Units for duty factor
None, it is a percentage
69
Duty factor ranges in clinical imaging
from 0.2% to 0.5%
70
Duty factor is determined by
Sound source only
71
Is duty factor adjustable by sonographer
Yes, by changing depth
72
Relationship between duty factor and depth
Inverse
73
Duty factor=
(pulse duration/pulse rep period) x 100
74
Longer pulses= _ duty factor
High
75
The maximum value for duty factor is _ and is achieved with _
100% Continuous wave sound
76
The minimum value for duty factor is _ and exists when _
0% The transducer is silent
77
Typical value for duty factor
0.2%
78
The system listens _ times longer than it transmits
500
79
Shallow imaging: _ listening
Less
80
Shallow imaging: _ PRP
Shorter
81
Shallow imaging: _ PRF
Higher
82
Shallow imaging: _ PRF
Higher
83
Shallow imaging: _ duty factor
Higher
84
Deep imaging: _ listening
More
85
Deep imaging: _ PRP
Longer
86
Deep imaging: _ PRF
Lower
87
Deep imaging: _ duty factor
Lower
88
Determined by source
Pulse duration PRP PRF Duty factor
89
Determined by source and medium
Spatial pulse length
90
Does not change with imaging depth
Pulse duration | Spatial pulse length
91
Changes with imaging depth
PRP PRF Duty factor
92
The parameters that describe a single cycle can describe both continuous and pulsed wave sound
Period | Frequency Wavelength Propagation speed

Physics (25 decks)

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