# Ultrasound Physics

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1. pressure, density, and particle vibration; sound wave quantities that vary in space and time
acoustic variables
2. region of low density and pressure in a compressional wave
rarefaction
3. reduction in differences between small and large amplitudes. region of high density and pressure in a wave
compression
4. wave in which the particle motion is parallel to the direction of wave travel (compressional wave)
longitudinal wave
5. number of cycles per second
frequency
6. unit of frequency, one cycle per second; unit of pulse repetition frequency, one pulse per second.
hertz
7. T/F
A wave is a traveling variation of some quantity or quantities.
True
8. T/F
Sound is a traveling variation of acoustic variables.
True
9. T/F
Acoustic variables include pressure, density, and particle motion.
True
10. T/F
A cycle is one complete variation in pressure or other acoustic variable.
True
11. T/F
Frequency is the number of cycles in a wave that occur in 1 second.
True
12. One hertz is one cycle per second. The abbreviation for hertz is Hz.
True
13. T/F
One kilohertz is 1000 cycles per second. The abbreviation for kilohertz is kHz.
True
14. T/F
One megahertz is one million cycles per second. The abbreviation for megahertz is MHz.
True
15. sound of frequency too low for human hearing (<20 hertz)
Infrasound
16. sound of frequency too high for human hearing (>20,000 hertz)
Ultrasound
17. imaging depth
penetration
18. time per cycle
period
19. the common unit for period in ultrasound
microsecond (μs)
20. Period = 1/Frequency
T (μs) = 1 / f (MHz)
21. If frequency increases, period _______.
decreases
22. length of space over which a cycle occurs
wavelength
23. T/F
Wavelength is commonly expressed in millimeters.
True
24. the speed with which a wave moves through a medium
propagation speed
25. Wavelength is = propagation speed (c) divided by frequency
λ (mm) = c (mm/μs) / f (MHz)
26. If frequency increases, wavelength ______.
decreases
27. the resistance of a material to compression
stiffness
28. Propagation speeds are highest in ______ and lowest in ______.
• solids (highest)
• gases (lowest)
29. Propagation speed values in soft tissue range from _____ to _____.
1.44 to 1.64 mm/μs
30. The average propagation speed of sound in tissue is _____.
1.54 mm/μs
31. progression of travel
propagation
32. sound propagation in which the propagation speed depends on pressure causing the wave to shape to change and harmonics to be generated
nonlinear propagation
33. the primary frequency in a collection of frequencies that can include odd and even harmonics and subharmonics
fundamental frequency
34. frequencies that are even and odd multiples of another, commonly called fundamental or operating frequency
harmonics
35. a wave in which cycles repeat indefinitely; not pulsed.
continuous wave
36. ultrasound produced in pulsed form by applying electric pulses or voltages of one or a few cycles to the transducer
pulsed ultrasound
37. a brief excursion of a quantity from its normal value; a few cycles
pulse
38. T/F
With continuous wave ultrasound, cycles repeat indefinitely. Pulsed ultrasound consists of pulses separated by gaps in time. A pulse is a few cycles of ultrasound.
True
39. number of pulses per second
pulse repetition frequency or pulse repetition rate
40. interval of time from the beginning of one pulse to the beginning of the next
pulse repetition period
41. PRF is commonly expressed in
kilohertz
42. PRP is commonly expressed in
milliseconds
43. PRP (ms) = 1 / PRF (kHz)
44. If pulse repetition frequency increases, pulse repetition period ______.
decreases
45. Interval of time from beginning to end of a pulse
pulse duration
46. T/F
Shorter pulses, compared with longer ones, improve the quality of sonographic images.
True
47. T/F
Sonographic pulses are typically 2 or 3 cycles long. Doppler pulses are typically 5 to 30 cycles long.
True
48. Pulse duration = period (time for one cycle) X number of cycles in the pulse (n)
PD (μs) = n X T (μs)
49. T/F
Pulse duration is the time for a pulse to occur.
True
50. T/F
If frequency is increased, period is decreased, reducing pulse duration. If the number of cycles in a pulse is reduced, pulse duration is decreased.
True
51. fraction of time that pulsed ultrasound is on
duty factor
52. T/F
Longer pulses increase the duty factor because the sound is on more of the time.
True
53. DF = PD (μs) / PRP (μs)
DF =( PD (μs) X PRF (kHz) ) / 1000 (kHz / MHz)
54. T/F
If pulse duration increases, duty factor ______.
increases
55. if PRF increases, pulse repetition period _____ and duty factor ________.
• decreases
• increases
56. length of space over which a pulse occurs
spatial pulse length
57. Spatial pulse length = length of each cycle X the number of cycles in the pulse
SPL (mm) = n X λ (mm)
58. T/F
Spatial pulse length is the length of space that a pulse takes up.
True
59. T/F
If the number of cycles in a pulse increases, spatial pulse length increases. If frequency increases wavelength and spatial pulse length decrease.
True
60. T/F
Shorter pulses improve sonographic image resolution.
True
61. range of frequencies contained in an ultrasound pulse; range of frequencies within which a material, device, or system can operate.
bandwidth
62. bandwidth divided by operating frequency
fractional bandwidth
63. nonspecific term referring to amplitude or intensity
strength
64. maximum variation of an acoustic variable or voltage
amplitude
65. power divided by area
intensity
66. rate at which work is done; rate at which energy is transferred
power
67. T/F
If beam power increases, intensity increases. If beam area decreases (focusing), intensity increases.
True
68. force multiplied by displacement
work
69. conversion of sound to heat
absorption
70. decrease in amplitude and intensity with distance as a wave travels through a medium
attenuation
71. portion of sound returned from a media boundary; echo
reflection
72. diffusion or redirection of sound in several directions upon encountering a particle suspension or a rough surface
scattering
73. reflection
echoes
74. unit of power or intensity ratio; the number of decibels is 10 times the logarithm (to the base 10) of the power or intensity ratio.
decibel
75. attenuation per centimeter of wave travel
attenuation coefficient
76. time it takes a wave to vibrate a single cycle
period
77. Period is determined by the ________ _______.
sound source
78. the number of particular events that occur in a specific duration of time. in ultrasound, the number of cycles that occur in one second
frequency
79. Diagnostic range of frequency in ultrasound
2 MHz - 10 MHz
80. Frequency is determined by the ______ _______.
sound source
81. Frequency and period have what type of relationship
inversely proportional and a reciprocal relationship
82. distance or length of one complete cycle
wavelength
83. wavelength is determined by the ______ ______ and the _____.
sound source and medium
84. shorter wavelengths produce ______ quality images
higher
85. frequency and wavelength have a _______ relationship as long as they are in the same medium
inverse
86. the distance that a sound wave travels through a medium in 1 second
propagation speed
87. propagation speed is determined by the
medium
88. order the medium that sound travels the fastest in (normal states of matter)
• solids
• liquids
• gases
89. 2 medium characteristics that affect propagation speed
• stiffness
• density
90. propagation speed and stiffness are ______ related
directly
91. other name for stiffness
bulk modulus
92. propagation speed and density are ______ related
inversely
93. the difference in the maximum value and the average or undisturbed value of an acoustic variable may also be the difference between the minimum and the average
amplitude
94. amplitude is _______ by the sonographer
95. the difference between the maximum and minimum values of an acoustic variable
peak-to-peak amplitude
96. rate of energy transfer
power
97. power is measured in
watts
98. power is _____ by the sonographer
99. power is ______ to the amplitude ______
• proportional
• squared
100. concentration of energy in a sound beam
intensity
101. intensity = power/cross sectional area
102. Intensity is measured in
watts/cm ^2
103. intensity is _______ by the sonographer
104. intensity and power are ________
proportional
105. intensity is proportional to the amplitude _______
squared
106. What parameters describe pulsed sound?
• pulse duration
• pulse repetition period
• pulse repetition frequency
• duty factor
• spatial pulse length
107. the actual time from the start of a pulse to the end of that pulse
pulse duration
108. pulse = # cycles X period
109. pulse duration = # cycles / frequency
110. pulse duration is ______ to the number of cycles in the pulse
proportional
111. pulse duration is ______ proportional to the period
directly
112. Pulse duration is _______ proportional to the frequency
directly
113. long pulses have either
• many cycles
• individual cycles with long periods
114. short pulses have either
• few cycles in the pulse
• individual cycles with short periods
115. clinical imaging uses pulses that contain how many cycles
2-4
116. distance from the start of a pulse to the end of that pulse
spatial pulse length
117. SPL = # of cycles X λ
118. SPL is ______ proportional to the number of cycles
directly
119. SPL is ______ proportional to the wavelength
directly
120. SPL is _______ proportional to frequency
inversely
121. The major difference between SPL and PD
• SPL refers to distance
• PD refers time
122. time from the start of one pulse to the start of the next pulse . includes the pulse duration and the listening time
PRP
123. PRP is related to the ____ of view
depth
124. PRP and imaging depth are ______ related
directly
125. the number of pulses that are transmitted into the body each second
Pulse repetition frequency
126. depth of view and PRF are ______ related
inversely
127. PRP and PRF are _______ related and ______
inversely related and reciprocals
128. seconds (PRP) go with hertz (PRF)
milliseconds (PRP) go with ______ (PRF)
kilohertz
129. the percentage of time or fraction of time that the system is transmitting a pulse
duty factor
130. duty factor% = (pulse duration / PRP) X 100
131. a duty factor of 1 would refer to a ______ wave
continuous wave
132. a duty factor of 0 means the system is _____
off
133. duty factor is _____ related to imaging depth
inversely
134. What are the 7 parameters required to completely characterize a sound wave?
• period
• frequency
• wavelength
• speed
• amplitude
• power
• intensity
135. tissue/material through which the sound waves travel
medium
136. 3 parameters describe the size, magnitude, or strength of a sound wave
• amplitude
• power
• intensity
137. 10^9 giga G billion
10^6 mega M million
10^3 kilo k thousand
10^2 hecto h hundred
10^1 deca da ten
10^-1 deci d tenth
10^-2 centi c hundredth
10^-3 milli m thousandth
10^-6 micro µ millionth
10^-9 nano n billionth

### Card Set Information

 Author: Qwizdom100 ID: 104276 Filename: Ultrasound Physics Updated: 2012-08-26 16:27:55 Tags: Test Folders: Description: Notes Show Answers:

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