Test 2- Pulsed And Intensity Flashcards
0
Q
Cycle is on….
A
Transmit
1
Q
What is pulsed Ultrasound?
A
Collection of cycles that travel together.
Must have a beginning and an end.
2
Q
Cycle is off…
A
Receive
3
Q
What are Pulsed Wave Parameters?
A
- pulse duration
- spatial pulse length
- pulse repetition period
- pulse repetition frequency
- duty factor
4
Q
What is Pulse Duration?
A
- on time - talking time - transmit time
- actual time from the start to the end of a pulse
- amount of time the pulse lasts
5
Q
What are the units of pulse duration?
A
seconds, microseconds
6
Q
Pulse Duration is the what?
A
Time it takes for one pulse to occur.
-determined by the number of cycles in each pulse and the period of the cycle
7
Q
Can pulse duration be changed by the sonographer?
A
No.
8
Q
Pulse duration is a characteristic of what?
A
the transducer/sound source
9
Q
What is the pulse duration for clinical imaging?
A
0.5-2 microseconds
10
Q
In clinical imaging, a pulse is comprised of _____ cycles.
A
2-4
11
Q
What is the formula for pulse duration?
A
PD = # of cycles in pulse x period PD = # of cycles in pulse / frequency
12
Q
Pulsed Duration - the transducer is made of _________ or _________ that stop the ringing and shorten the pulse for improved axial resolution.
A
backing layers, damping layers
13
Q
short pulse = what?
A
better axial resolution
14
Q
PD is directly related to ________ and number of _______ in the pulse.
A
Duty Factor, cycles
15
Q
PD is inversely related to _______.
A
PRF
16
Q
What is Spatial Pulse Length?
A
length or distance that a pulse occupies in space.
distance from the start of a pulse to the end of that pulse.
17
Q
What are the units for Spatial Pulse Length?
A
mm
18
Q
What is the spatial pulse length for clinical imaging?
A
0.1 to 1 mm
19
Q
Spatial pulse length is determined by what?
A
the sound source and the medium
20
Q
Can the Spatial Pulse Length be changed by the sonographer?
A
No.
21
Q
What is the formula for Spatial Pulse Length?
A
SPL = # of cycles x wavelength
22
Q
Why are shorter pulses desirable?
A
Better AXIAL RESOLUTION
23
Q
SPL is directly related to _______ and ________.
A
wavelength, number of cycles
24
SPL is inversely related to ________.
frequency
25
What is Pulse Repetition Period?
Time from the start of one pulse to the start of the next pulse.
Includes talking and listening times.
Time when system has a pulse and when it has no pulse.
26
What are the units for PRP?
time
27
What is the PRP for clinical imaging?
100 microseconds to 1 msec
28
PRP is determined by what?
sound source
29
Can the PRP be changed by the sonographer?
Yes. PRP changes by the sonographer when depth of view is changed and then listening time increases.
30
PRP is directly related to what?
imaging depth
31
PRP is inversely related to what?
PRF
32
As imaging depth increases _________ increases.
PRP
33
As imaging depth decreases ________ decreases.
PRP
34
What is Pulse Repetition Frequency?
Number of pulses in one second.
| Not related to the "frequency"
35
What is pulse repetition frequency determined by?
depth of view
36
What is the formula for PRF max?
PRF max = speed of sound in the medium / 2 x (max depth)
37
What are the units for PRF?
Hertz
38
What is the PRF in clinical imaging?
1,000-10,000 Hz (pulses per second)
39
What is PRF determined by?
sound source
40
PRF depends on what?
imaging depth
41
Can PRF be changed by the sonographer?
Yes. It changes by the sonographer when depth of view is changed
42
Shallow image = ______ PRF.
higher
43
Deeper image = ______ PRF.
lower
44
PRF is directly related to __________.
duty factor
45
PRF is inversely related to ________ and ________.
imaging depth and PRP
46
PRF determines what?
how fast images are generated
47
PRF of 5kHz means ________.
5000 pulses per second
48
What is Duty Factor?
Percentage of time that the system is "talking."
| Percentage of time that the system is ON
49
Duty factor of 100% = ?
continuous wave
50
DF of 1% or less = ?
pulsed wave
51
DF of 0% = ?
equipment is OFF
52
What is duty factor determined by?
sound source
53
Can duty factor be changed by the sonographer?
Yes. It is changed by the sonographer when the depth of view is changed.
54
The duty factor of clinical imaging is what?
0.1% to 1.0%
55
Duty factor for Doppler is what?
0.5% to 5.0%
56
What is the formula for duty factor?
```
DF = Pulse Duration / Pulse repetition period x 100
DF = talking time / talking and listening time
```
57
Duty factor increases when....
- imaging depth decreases
- shallower imaging
- PRP decreases
- PRF increases
58
Duty factor is directly related to ______ and ______.
PRF and PD
59
Duty factor is inversely related to ______.
PRP
60
For shallow imaging in pulsed ultrasound there is......
- less listening
- shorter PRP
- higher PRF
- higher duty factor
61
For deeper imaging in pulsed ultrasound there is.....
- more listening
- longer PRP
- lower PRF
- lower duty factor
62
Duty Factor is important for determining _______. Why?
intensity, it relates to bioeffects
63
What is bandwidth?
range of frequencies
64
Shorter pulse has ________ bandwidth.
broad
65
Longer pulse has _______ bandwidth.
narrow
66
What parameters are changed by imaging depth?
PRP, PRF, Duty Factor
67
What is intensity?
the amount or degree of strength of sound per unit area
68
What is the unit of intensity?
W / cm^2
69
Intensity relates to what?
the strength of the sound beam
70
Intensity ~ ?
| Intensity ~ ?
intensity ~ power
| intensity ~ amplitude ^2
71
What is intensity determined by?
determined by the system
72
Why is intensity important?
related to bioeffects
73
Can intensity be changed by the sonographer?
Yes.
74
Intensity is the concentration of what?
the power in a beam
75
What is the formula for intensity?
power (watts) / beam area (cm^2)
76
Increasing _______, increasing intensity
power
77
increasing _______, decreases intensity.
area
78
decreasing _______, increases intensity.
area
79
What is energy?
the ability to do work
80
______ is energy transferred divided by time.
Power
81
Intensity varies across what?
the sound beam
82
Intensity is highest in the _______ and falls off at the ________.
center, periphery
83
intensity is not uniform across the ______ and with ______ ______ not uniform in time.
beam, pulsed wave
84
With pulsed wave, the intensity varies in _____.
time
85
With pulsed wave, the intensity varies in _______.....
space
86
Intensity
Peak-
Average-
Peak- the maximum value
| Average - the middle value
87
Intensity
| Spatial (where) Peak -
maximum intensity along the beam
| determined by focusing
88
Intensity
| Spatial (where) average-
Spatial (where) average- average over the beam
89
Spatial (where) -
referring to space
90
Which is higher SP or SA?
SP is always higher
91
For ultrasound the ________ ________ is at the center of the beam and it _______ as the beam spreads.....
strongest intensity, reduces
92
Temporal (when) -
referring to all time (transmit and receive)
93
temporal (when) peak-
maximum intensity in the pulse
94
temporal (when) average -
intensity over the time of the PRP
95
Pulse average -
the intensity averaged over the time of the pulse
96
For a given pulse, highest to lowest would be.....
TP, PA, TA
97
Why are the TA and PA equal for continuous wave?
because there is no pulse
98
Spatial peak, temporal peak SPTP
maximum value in space and time
99
SATP
Spatial average, temporal peak
100
SPPA
Spatial peak, pulse average
101
SAPA
Spatial average, pulse average
102
SPTA
Spatial peak, temporal average
103
What is the most relevant intensity with respect to tissue heating?
SPTA
104
SATA
Spatial average, temporal average
105
the beam is only transmitting _______% in PW.
less than 1%
106
99% of the time the intensity is _____.
0
107
Spatial intensity -
ultrasound beam does not have the same intensity at different locations
108
temporal intensity -
ultrasound beam does not have the same intensity at different times
109
List the intensities from high to low.
SPTP > SATP > SPPA > SAPA > SPTA > SATA
110
Beam uniformity factor or coefficient or ratio (BUR) SP/SA -
describes sound beam in space
111
BUR
ratio of center intensity to average
unitless
always greater than 1
112
For continuous wave - SPTA and SPPA and SPTP are _____.
the same
113
For continuous wave SATA and SAPA and SATP are ______.
the same
114
What is intensity determined by?
sound source
115
Can intensity be changed by the sonographer?
Yes. Sonographer changes when changing power
116
hydrophone or microprobe
device used to measure output intensity of the transducer
117
below 100 mW/cm^2 -
unfocused sound
118
below 1000 mW/cm^2 -
focused sound
119
higher intensities are needed to produce bioeffects with a ________ transducer.
focused
