Ultrasound Physics Final

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Qwizdom100
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Ultrasound Physics Final
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2011-12-03 16:17:14
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Edelman Chapters 13
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  1. Name the Metric System from Billion to Billionth
    • 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
  2. What is an appropriate unit for area?
    sqaure yards
  3. What is an appropriate unit for volume?
    cm^3
  4. How many milliliters are in 8 liters?
    8000 ml
  5. How many centimeters are in 3 meters?
    300 cm
  6. How many kilometers are in 3000 meters?
    3 km
  7. What is the reciprocal of 100?
    1/100 or 0.01
  8. What is the reciprocal of 1/8?
    8
  9. How many hertz is 3 MHz?
    3,000,000 hertz
  10. How many milliliters are contained in a jar filled with 5 liters of fluid?
    5000 ml
  11. How many liters are contained in 80 ml of fluid?
    0.080 L
  12. How many times bigger is a thousand than ten?
    100 times
  13. How much bigger is a billion than a million?
    1000 times
  14. How much smaller is a hundred than a thousand?
    one-tenth
  15. Def. biologic tissue
    media
  16. All waves carry _____ from one location to another.
    energy
  17. Sound is a _____ wave in which particles in the medium move.
    mechanical
  18. Def. Area of increased pressure (squeezed together)
    compressed
  19. Def. Area of decreased pressure (stretched apart)
    rarefied
  20. Sound waves travel in _____ lines.
    straight
  21. Sound waves are ______ waves.
    longitudinal
  22. Def. the effects of the medium upon the sound wave
    acoustic propagation properties
  23. Def. the effects of the sound wave upon the biologic tissue through which it passes
    biologic effects
  24. Name the acoustic variables
    pressure, density, distance
  25. What is pressured measured in?
    Pascals (Pa)
  26. Def. concentration of force in an area
    pressure
  27. Def. concentration of mass in a volume
    density
  28. Def. measure of particle motion
    distance
  29. What is density measured in?
    kg/cm^3
  30. What is distance measured in?
    ft, cm, mile, etc...
  31. What are the acoustic parameters?
    • period
    • frequency
    • amplitude
    • power
    • intensity
    • wavelength
    • propagation speed
  32. Def. particles that move in a direction that is perpendicular to the direction that the wave propagates
    transverse wave
  33. Def. particles that move in the same direction that the wave propagates
    longitudinal
  34. Def. when the peaks or troughs of a pair of waves occur at the same time
    In-Phase Waves
  35. Def. when the peaks or troughs of a pair of waves occur at different times
    Out-Of-Phase
  36. Def. when a pair of waves lose their individual characteristics and combine to form a single wave
    interference
  37. Def. the interference of a pair of in-phase waves
    constructive interference
  38. Def. the interference of a pair of out-of-phase waves
    destructive interference
  39. Waves of with different ______ will undergo constructive and destructive interference.
    frequencies
  40. Two waves are traveling in a medium and arrive at a location at the same time. What event takes place?
    interference (we don't know if they are in-sync)
  41. What is the source of a sound wave?
    ultrasound system and transducer
  42. Def. the time it takes a wave to vibrate a single cycle, or the time from the start of a cycle to the start of the next cycle
    period
  43. What is period measured in?
    seconds, ms, hours, etc...
  44. What are the typical values for period?
    .1µs to .5µs
  45. Def. the number of particular events that occurs in a specific duration of time
    frequency
  46. What is frequency measured in?
    Hertz
  47. What are the typical values for frequency?
    2 MHz to 10 MHz
  48. Def. less than 20 Hz
    infrasound
  49. Def. between 20 Hz to 20 kHz
    audible sound
  50. Def. greater than 20 kHz
    ultrasound
  51. What are the relationships between period and frequency?
    • inversely related
    • reciprocals
  52. What are the bigness parameters?
    • amplitude
    • power
    • intensity
  53. Def. the difference between the maximum or minimum value and the average or undisturbed value of an acoustic variable
    Amplitude
  54. What units can amplitude be measured in?
    • pascals
    • g/cm^3
    • distance
    • decibels (dB)
  55. What are the typical values of amplitude?
    1 MPa to 3 MPa
  56. Def. the difference between maximum and minimum values of an acoustic variable
    peak-to-peak amplitude
  57. Def. the rate of energy transfer or the rate at which work is performed
    power
  58. What is power measured in?
    watts
  59. What are the typical values of power?
    4 - 90 milliwatts
  60. How is power and amplitude related?
    power is proportional to amplitude squared
  61. How is intensity and amplitude related?
    intensity is proportional to amplitude squared
  62. How is intensity and power related?
    intensity is proportional to power
  63. Amplitude has increased by a factor of 3. How much has the power changed?
    9-fold
  64. Amplitude has decreased by 1/2. How much has power changed?
    1/4
  65. Def. the concentration of energy in a sound beam
    intensity
  66. What is intensity measured in?
    W/cm^2
  67. What are the typical values of intensity?
    .01 - 300 W/cm^2
  68. What is the formula for intensity?
    intensity (W/cm^2) = power (w) / area (cm^2)
  69. Def. the distance or length of one complete cycle
    wavelength
  70. What is wavelength measured in?
    meters, inches, cm, etc...
  71. What are the typical values of wavelength?
    .15 - .8 mm
  72. What determines wavelength?
    sound source and medium
  73. What is the formula between wavelength and frequency?
    wavelength (mm) = 1.54 mm/µs / frequency (MHz)
  74. What type of wavelength creates better images?
    shorter wavelength
  75. Def. the distance that a sound travels through a medium in 1 second
    propagation speed
  76. What is propagation speed measured in?
    meters per second, mm/µs
  77. What are the typical values of propagation speed?
    500 m/s to 4000 m/s
  78. What determines the propagation speed?
    medium
  79. What is the speed of sound in soft tissue?
    1,540 m/s
  80. What is the formula for speed of sound?
    speed (m/s) = frequency (Hz) x wavelength (m)
  81. What two characteristics of a medium effect the speed of sound?
    stiffness and density
  82. Def. describes the ability of an object to resist compression
    stiffness
  83. Def. describes the relative weight of a material
    density
  84. What is the relationship between stiffness and speed?
    directly related
  85. What is the relationship between density and speed?
    inversely related
  86. What terms can describe stiffness? They are opposite of stiff.
    elasticity and compressiblity
  87. What acoustic parameters are determined by the sound source?
    period, frequency, amplitude, power, intensity, wavelength
  88. What acoustic parameters are reciprocals?
    period and frequency
  89. What acoustic parameters can be adjusted by the sonographer?
    amplitude, power, intensity
  90. What acoustic parameter is determined by both the sound source and the medium?
    wavelength
  91. What acoustic parameter is determined by the medium only?
    propagation speed
  92. T/F A wave with a frequency of 15,000 MHz is ultrasonic?
    true
  93. T/F If amplitude is increased to 3 times it's original value, intensity is increased 6-fold.
    false 9-fold
  94. T/F If power is halved intensity is reduced by 1/4.
    false it's halved
  95. T/F propagation speed increases as frequency increases.
    False
  96. Medium 1 has a density of 9 and a stiffness of 6.
    Medium 2 has a density of 8 and a stiffness of 6.
    Which medium will be slower?
    Medium 1
  97. If the power in a beam is 1 watt and the area is 5 cm^2, what is the beam's intensity?
    .2 W/cm^2
  98. If intensity remains the same while the power is doubled, what has happened to the beam area?
    doubled
  99. A sound beam travels a total of 10 cm in 2 seconds. What is the speed of sound?
    5 cm/sec
  100. T/F Propagation speed increases as frequency increases.
    false
  101. T/F Propagation speed increases as frequency decreases.
    False
  102. T/F Propagation speed does not change as frequency increases.
    True
  103. What is the wavelength of 3 MHz sound in soft tissue?
    .51 mm
  104. The effects of sound waves on tissue in the body are called ______.
    bioeffects
  105. The effects of tissue on sound waves are called ______.
    Acoustic propagation properties
  106. The effects of a medium on an ultrasound wave are called ________.
    acoustic propagation properties
  107. T/F Continuous wave sound can create diagnostic images.
    false pulse sound
  108. What is pulsed sound?
    a collection of cycles that travel together
  109. 2 components of pulsed sound
    • transmit, talking, "on" time
    • receive, listening, "off" time
  110. Def. the actual time from the start of a pulse to the end of that pulse
    Pulse duration
  111. What is pulse duration measured in?
    seconds, µs, ms, etc...
  112. What are the typical values of pulse duration?
    .3µs to 2µs
  113. What are the formulas for pulse duration?
    • pulse duration (µs) = # of cycles x period (µs)
    • pulse duration (µs) = # of cyles / frequency (MHz)
  114. What are the 2 characteristics of long duration pulses?
    • many cycles in the pulse
    • individual cycles with long periods
  115. What are the 2 characteristics of short duration pulses?
    • few cycles in the pulse
    • individual cycles with short periods
  116. Which type of pulse duration is desirable for imaging?
    shorter duration pulses improve image accuracy
  117. Def. the distance from the start to the end of a pulse
    Spatial Pulse Length
  118. What is spatial pulse length measured in?
    mm, inches, etc...
  119. What are the typical values for spatial pulse length?
    .1 to 1 mm
  120. What is the formula for spatial pulse length?
    spatial pulse length (mm) = # of cycles x wavelength (mm)
  121. What are 2 characteristics of long pulse length?
    • many cycles in the pulse
    • cycles with longer wavelengths
  122. What are the 2 characteristics of short pulse length?
    • fewer cycles in the pulse
    • cycles with shorter wavelengths
  123. Which type of spatial pulse length is more desirable?
    shorter pulses create more accurate images
  124. Def. the time from the start of one pulse to the start of the next pulse
    Pulse Repetition Period
  125. What is pulse repetition period measured in?
    units of time, ms
  126. What are the typical values for pulse repetition period?
    100µs to 1 ms
  127. Pulse repetition period is controlled by what?
    Sound source specifically imaging depth
  128. Def. the maximum distance into the body that an ultrasound system is imaging
    Depth of View
  129. What are the 2 components of pulse repetition period?
    • transmit time
    • receive time
  130. What is transmit time also known as?
    pulse duration
  131. What happens to the depth of view when the listening time and pulse repetition period lengthen?
    deeper imaging
  132. What happens to the depth of view when the listening time and pulse repetition period shorten?
    shallower imaging
  133. Def. the number of pulses that an ultrasound system transmits into the body each second
    Pulse Repetition Frequency
  134. What is pulse repetition frequency measured in?
    hertz
  135. What are the typical values of pulse repetition frequency?
    1000 to 10000 hertz
  136. How is pulse repetition frequency and depth of view related?
    inversely
  137. What are the relationships between pulse repetition frequency and pulse repetition period?
    inversely related and reciprocals
  138. What is the easiest formula to remember PRF and PRP?
    PRF x PRP = 1
  139. T/F Two waves can have identical pulse repetition frequencies , even if their pulse repetition periods are different.
    False
  140. T/F Two waves can have identical PRFs, even if their periods are different.
    True
  141. T/F PRF and PRP are determined only by the imaging depth.
    True
  142. Def. the percentage or fraction of time that the system is transmitting a pulse
    Duty Factor
  143. What is unit for duty factor?
    none. it's a percentage therefore dimensionless
  144. What are the typical values for Duty Factor?
    .2% to .5%
  145. What is the relationship between depth of view and duty factor?
    inversely related
  146. What is the formula for duty factor?
    duty factor (%) = (pulse duration / PRP) x 100
  147. What are the factors that determine shallow imaging?
    • less listening
    • shorter PRP
    • higher PRF
    • higher duty factor
  148. What are the factors that determine deeper imaging?
    • more listening
    • longer PRP
    • lower PRF
    • lower duty factor
  149. Def. refers to the intensity of the beam at different locations or distances
    Spatial Intensity
  150. Def. the maximum intensity
    peak intensity
  151. Def. the mathematical middle intensity
    Average Intensity
  152. Def. refers to the intensity at all time, transmit and receive
    Temporal Intensity
  153. Def. refers to the intensity at the transmit time
    Pulsed intensity
  154. Def. the beams intensity at the location where it is maximum
    spatial peak intensity
  155. Def. the beams intensity across the entire cross-sectional area
    spatial average intensity
  156. Def. the beams intensity at the instant in time of its maximum value
    temporal peak
  157. Def. the average intensity during the most intense half-cycle
    I max
  158. Def. the average intensity during the pulse duration
    pulse average intensity
  159. Def. averaging the intensity during the entire PRP (includes both the transmit and recieve times)
    temporal average intensity
  160. T/F Intensities may be reported in various ways with respect to time and space.
    True
  161. The different measurements of intensities are important in the study of ________.
    bioeffects
  162. ______ intensity is the most relevant intensity with respect to tissue heating.
    SPTA
  163. What units are all intensities are measured in?
    watts/cm^2
  164. What intensity if the highest and which is the lowest?
    • SPTP is the highest
    • SATA is the lowest
  165. Def. describes the spread of a beam in space
    beam uniformity coefficient or SP/SA factor
  166. Def. describes the relationship of beam intensities with time
    duty factor
  167. Continuous wave ultrasound. The pulse average and temporal average intensities are the ______.
    Same
  168. T/F For continuous wave ultrasounds, SPTA = SPPA and SATA = SAPA.
    True
  169. T/F When pulsed and continuous waves have the same SPTP, the continous wave will have the higher intensity.
    True
  170. T/F When pulsed and continuous waves have the same SATP intensities, the continuous wave will have the higher SPTA intensity.
    True
  171. Rank the types of intensities from largest to smallest.
    SPTP > Im > SPPA > SPTA > SATA
  172. Def. the weakening of sound as it travels in the body
    attenuation
  173. Def. strengthening of the ultrasound signal
    amplifying
  174. Def. the unit that quantifies the strength of sound beams as they are created by tranducers and travel through the body
    Decibels
  175. Def. Decibels that are increasing in strength or getting larger.
    Positive Decibels
  176. Def. decibels that are decreasing in strength or getting smaller
    negative decibels
  177. The 3 decibel rule.
    a change of 3 decibel is equal to doubling or having the intensity of the ultrasound beam
  178. The 10 decibel rule.
    a change of 10 decibels it equal to 10-fold or one-tenth of the intensity of the ultrasound beam
  179. A reduction in the intensity of a sound beam to one-half of its original value is _____dB.
    -3 dB
  180. A reduction in the intensity of a sound beam to one-quarter of its original value is ______ dB.
    -6 dB
  181. -10 dB means that the intensity is reduced to ______ of its original value.
    one-tenth
  182. dB is a mathematical representation with a ______ scale.
    logarithmic and relative
  183. T/F We need one intensity to calculate dB.
    False
  184. A wave's intensity is 2mW/cm^2. There is a change of +9 dB. What is the final intensity?
    16 mW/cm^2
  185. 2 factors determine attenuation
    • path length
    • frequency of sound
  186. 3 processes contribute to attenuation
    • reflection
    • scattering
    • absorption
  187. Def. when the wave's energy strikes a boundary and is redirected back toward the sound source
    Reflection
  188. 2 types of reflection
    specular and diffuse
  189. Def. type of reflection when sound is reflected back by a smooth boundary and in only one direction
    Specular reflection
  190. Def. type of reflection when sound is reflected back by and irregular surface and radiates in more than one direction
    Diffuse reflection
  191. Def. random redirection of sound in many directions that occurs when the tissue interface is smaller or equal to the wavelength of the sound beam
    Scattering
  192. Def. a special form of scattering that occurs when the structure's dimensions are much smaller than the beam's wavelength and the sound wave is redirected equally in all directions
    Rayleigh Scattering
  193. Def. occurs when ultrasonic energy is converted into another energy form, such as heat
    absorption
  194. Def. the number of decibels of attenuation that occurs when sound travels one cm
    Attenuation coefficient
  195. What is the attenuation coefficient measured in?
    dB/cm
  196. What is the formula for total attenuation?
    total attenuation (dB) = atten coefficient (dB/cm) x distance (cm)
  197. What is the formula for attenuation coefficient in soft tissue?
    atten. coef. (dB/cm) = frequency (MHz) / 2
  198. Def. the distance that sound travels in a tissue that reduces the intensity of sound to one-half its original value
    half-value layer thickness
  199. What are typical values for half-value layer thickness?
    .25 - 1 cm
  200. What are synomyns for half-value layer?
    penetration depth, depth of penetration, half-boundary layer
  201. 2 factors that determine half-value layer thickness
    • the medium
    • the frequency of sound
  202. Def. the acoustic resistance to sound traveling in a medium
    impedance
  203. What is the formula for impedance?
    impedance (rayls) = density (kg/m^3) x prop. speed (m/s)
  204. What unit is impedance measured in?
    rayls
  205. What are the typical values for impedance?
    1.25 to 1.75 Mrayls
  206. What is another name for acoustic impedance?
    characteristic impedance
  207. page 87

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