Chapter 3 Flashcards
(99 cards)
1
Q
7 parameters that describe the features of a sound wave
A
Period Frequency Amplitude Power Intensity Wavelength Propagation speed
2
Q
The source of the sound wave is the
A
Ultrasound system and the transducer
3
Q
_ is the tissue through which the sound is traveling
A
Medium
4
Q
the time it takes a wave to vibrate a single cycle
A
Period
5
Q
Typical values: (period) in diagnostic ultrasound
A
Typically 0.06-0.5 microseconds
May be written as 6x10^-8 to 5x10^-7 or .000000006-.00000005
6
Q
Is period adjustable by the sonographer
A
No
7
Q
_ frequency goes deeper
A
Low
8
Q
_ frequency is used for superficial structures
A
High
9
Q
The number of particular events that occur in a specific duration of time
A
Frequency
10
Q
• In ultrasound, frequency of a wave =
A
Number of cycles per second
11
Q
Units for frequency
A
Hertz (Hz)
12
Q
1,000,000 cycles/second = 1_
A
MHz
13
Q
Typical values of frequency in ultrasound
A
2-15MHz
14
Q
Frequency affects _ & _
A
Penetration and image quality’s
15
Q
Frequency is determined by
A
Sound source only
16
Q
Is frequency adjustable by sonographer
A
No
17
Q
Infrasound
A
<20 Hz
18
Q
Audible sound
A
20-20,000Hz
19
Q
Ultrasound
A
> 20,000Hz (20MHz)
20
Q
Frequency and period have _ relationship
A
An inverse
21
Q
Frequency and period: if one remains constant what happens to the other
A
It remains unchanged
22
Q
Period and frequency are _
A
Reciprocals
23
Q
If a wave has a frequency of 4Hz, the period would be
A
1/4 second
24
Q
Seconds & Hz
Microseconds & megahertz are examples of
A
Complimentary units
25
1Hz=
1 event per second
26
Event can mean
Cycle, frames, beat, etc
27
3 bigness parameters
Amplitude
Power
Intensity
28
Bigness parameters describe
Size, magnitude, or strength of a wave
29
Bigness parameters (amplitude, power, intensity) are determined by what
Sound source
30
The difference between the maximum value and the average or undisturbed/ baseline value of an acoustic variable. The difference between the minimum value and the average value
Amplitude
31
Bigness may be described in
Decibels
32
Units for amplitude
Can have units of any of the acoustic variables
| Decibels, pascals, g/cm^3, cm, inches, etc
33
Amplitude: typical values
```
range from 1 million pascals (1 MPa) to 3
million pascals (3 MPa)
```
34
Amplitude is determined by
initially by sound source only. As the wave travels through the body, the amplitude decreases. The rate of which depends on the characteristics of the sound wave and the medium
35
Can amplitude be changed by the sonographer
Yes
36
The difference between the maximum and minimum values of an acoustic variable
Peak to peak amplitude
37
_ is twice the value of amplitude
Peak to peak amplitude
38
The rate at which work is performed; the rate of energy transfer
Power
39
Units for power
Watss
40
Power: typical values
.004-.090 watts (4-90 milliwatts)
41
Power is determined by
initially by the sound source. Power decreases as sound propagates through the body (rate of decrease is dependent upon the medium)
42
Can power be changed by the sonographer
Yes
43
_ & _ describe the magnitude of a wave
Amplitude and power
44
When power increases what happens to amplitude
It increases too
45
Power is proportional to the waves
Amplitude squared
46
If amplitude is tripled, the power is
increased by a factor of nine
47
If the amplitude is halved, the power is
decreased by a factor of four
48
The concentration of energy in a sound beam • Intensity = power/area
Intensity
49
Intensity describes
The bigness of a wave
50
Units for intensity
W/cm^2
51
Intensity: typical values
.01-300 W/cm^2
52
Intensity is determined by
Initially by the sound source.
| Changes as it propagates through the body
53
Can intensity be changed by the sonographer
Yes
54
Relationship between intensity & power
Proportional
55
If a wave’s power is doubled, the intensity is
Doubled
56
Relationship between intensity & amplitude
Proportional to amplitude squared
57
If a wave’s amplitude is doubled, the intensity
increases four times its original value
58
The distance or length of one complete cycle
Wavelength
59
Units for wavelength
mm, m, units of length
60
Typical values of wavelength in soft tissue
0.1-0.8mm
61
Can wave length be changed by the sonographer
No
62
Equation for wavelength
L=c/f (L=1.54/f)
L (wavelength:mm)
c (propagation speed:mm/microseconds)
f (frequency: MHz)
63
Relationship between wavelength and frequency
Inverse
64
As frequency increases, wavelength _
decreases
65
Lower frequency= _ wavelength
longer
66
Wavelength of 1 MHz sound in soft tissue=
1.54mm
67
The rate at which a sound wave travels through a medium
Propagation speed
68
Units of speed
m/s, mm/microseconds
69
Typical value of speed
500 m/s-4,000 m/s depending in the tissue through which it is traveling
70
Speed is determined by
Medium
71
Can speed be changed by the sonographer
Not
72
TThe average biologic medium is called
Soft tissue
73
The speed of sound in soft tissue is
1,540 m/s or 1.54 mm/microseconds
74
Speed in tissue types from lowest to highest
```
Lung
Fat
Soft tissue
Liver
Blood
Muscle
Tendon
Bone
```
75
Sound travels slowest in what tissue
Lung
76
Sounds travels fastest in what tissue
Bone
77
Prop speed in air
330 m/s
78
Prop speed in water
1,480 m/s
79
Prop speed in metals
2,000-7,000 m/s
80
Sounds travels fastest in
solids
81
Sound travels slowest in
gases
82
Equation for speed
c=fXL
c: speed
f: frequency
L: wavelength
83
Two characteristics of a medium that affect the speed of sound
Stiffness
| Density
84
The ability of an object to resist compression, opposite of compressibility and elasticity
Stiffness
85
Stiffness is AKA
Bulk modulus
86
The relative weight of a material
Density
87
Stiffness and speed are _ related
Directly
88
The stiffer the medium, the _ the sound
Faster
89
Density and speed are _ related
Inversely
90
The denser the material, the _ the sound
Slower
91
Rule of thumbs
Stiffness & Speed= Same direction
| Density & Speed= Different direction
92
Stiffness has _ influence on speed than density
greater
93
Fastest media are
Stiff and not dense
94
Determined by source
```
Amplitude
Power
Period
Frequency
Intensity
```
95
Determined by medium
Speed
96
Determined by source and medium
Wavelength
97
Can be changed by sonographer
Amplitude
Power
Intensity
98
Can't be changed by sonographer
Wavelength
Period
Speed
Frequency
99
Reciprocals
Period
| Frequency
