us physics

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us physics
2010-06-09 15:48:50
final review

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  1. Sound waves are?
    A mechanical wave in which particles in a medium move. Sound travels in a stright line. Sound waves are longitudinal wave
  2. Acoustic propagation properities are?
    The effects of the cound wave upon the biological tissue through which it passes.
  3. The acoustic variables?
    Pressure ( pascals), density (kg/cm^3), and distance (cm,mm)
  4. Acoustic parameters
    Help describe the waves features
  5. The 7 acoustic parameters?
    Period, frequency, amplitude, power, intensity, wavelegnth, propogation speed.
  6. Tranverse waves?
    Particles move in a direction that is perpendicular (right angles) to the direction that the wave popagates.(string shakeing up/down)
  7. Longitudinal waves?
    particles move in the same direction that the wave propagates. (example sound).
  8. Inphase waves?
    Peaks occur at the same time and at the same location
  9. Out of phase waves?
    Peaks occur at different times. (out of step)
  10. Interference?
    When multiple beans arrive at same location and the waves loose their individual characteristic at that moment to combine to form a single wave
  11. Constrictive Interference?
    Intereferance of a pair of inphase waves results in the formation of a single wave of greater amplitude than either of its componets
  12. Destructive Interference?
    Interference of a pair of out of phase waves resulting in the formation of a single wave of lesser amplitude than either of its componets.
  13. Parameters?
    Describe features of a sound wave
  14. Period?
    Time it takes a wave to vibrate a single cycle/ time from start of one cycle to the start of the next cycle.
  15. Units of period?
    untis of time: seconds, ms, hours, days
  16. Period is determined by?
    Sound source. It is not adjustible by sonographer
  17. Frequency?
    The number of events that occurs in a sepcific duration of time.
  18. Units of frequency?
    units per second, 1/second,hertz(per second).
  19. Frequency is determined by?
    Sound source/ It is not adjustible by spnpgrapher
  20. Infrasound?
    less than 20Hz.
  21. Audible sound?
    between 20Hz and 20kHz.
  22. Ultrasound?
    Greater than 20kHz.
  23. Period and frequency are
    Reciprocals of each other
  24. The three parameters that describe the bigness of a sound wave?
    Amplitude, power, intensity
  25. Amplitude?
    Is the bigness of a wave.
  26. Units of amplitude?
    Pressure(pascals), density(g/cm^3), particle motion(cm,inches,any)
  27. Amplitdue is determined by?
    The sound source. It is adjustible by the sonographer
  28. Peak to peak amplitude
    If the difference between maxium and minimun values of an acoustic variable.
  29. Power?
    Is the rate of energy transfer or th rate at which work is performed
  30. Units of power?
  31. Power is determined by?
    Sound source. It is adjustable by sonographer
  32. Power and amplitude?
    Power is porportional to amplitude squared
  33. Intensity?
    The concentration of energy in a sound beam.
  34. Intensity ='s?
    Intensity(W/cm^2)= power(w)/area(cm^2).
  35. Units of intensity
    Watts/square centimeter, or W/cm^2
  36. Intensity is determined by?
    Sound source.It is adjustable by sonographer
  37. Intensity is?
    Poroprtional to power and amplitude squared.
  38. Wavelegnth?
    The distance or legnth of one complete cycle.
  39. Units of wavelegnth?
    mm,meters, any other unit of legnth.
  40. Wavelegnth is determined by
    Both the source and the medium. It is not adjustable by sonographer.
  41. To calculate wavelegnth
    1.54mm/us(wavelegnth of sound in soft tissue)/ frequency(MHz).
  42. Propogation speed?
    The distance that a sound wave travels through a medium in 1 second.
  43. Units of propogation speed?
    meters per second, mm/us, or any dstance divided by time
  44. Propogation speed is determined by?
    The medium in which it is traveling. It is not adjustable by sonograpger
  45. Speed of sound in soft tissue
    1,540 m/s
  46. Sound travels?
    Fastest in solids(bone, tendon, muscle), Slower in liquids( blood,liver,soft tissue), slowest in gases(fat,lung,air).
  47. Two characteristics of a medium that affects the speed of sound?
    stiffness, density.
  48. Stiffness?
    The ability of an object to resist compression. Higher stiffness faster speed.
  49. Density?
    The relative weight of a meterial. Higher the density the lower the speed.
  50. What is determined by the sound source
    Period, frequency, amplitude, power ,intensity. Pulse duration.PRP.PRF. Duty factor
  51. What is determined by medium?
  52. What is determined by both source and medium?
    Wavelegnth. Spatial pulse legnth.
  53. What can be changed by sonographer
    Amplitude, power, intensity.
  54. Pulse duration?
    The actual time from the start of a pulse to the end of that pulse.
  55. Units of pulse duration
    units of time, us,ms,seconds
  56. Pulse duration is determined by?
    The sound source. It is not adjustable by sonographer
  57. To calculate pulse duration?
    pulse duration(us)= #cycles x period(us) pulse duration(us)=#cycles/frequency(MHz)
  58. Spatial pulse legnth?
    The distance that a pulse occupies in space from the start to the end of a pulse.
  59. Units of spatial pulse legnth?
    Units of distance, mm
  60. Spatial pulse legnth is determined by?
    Both the source and the medium. It is not adjustable by sonographer.
  61. Pulse repetition period?
    The time from the start of one pulse to the start of the next pulse.
  62. Units of PRP?
  63. PRP is determined by
    The sound source. It is adjustable by sonographer
  64. Pulse repetition frequency?
    The number of pulses than an ultrasound system transmits into the body each second
  65. Units of PRF?
    Units of HZ or per second.
  66. PRF is determined by?
    The sound source. It is adjestable by sonographer
  67. Duty factor?
    The percentage or fraction of time that a system is transmitting a pulse.
  68. Units of duty factor?
    A %.
  69. Duty factor is determined by?
    Sound source. It is adjustable by sonographer
  70. Spatial?
    Refers to distance or space.
  71. Peak?
    The maximun value.
  72. Average?
    The mathamatical middle
  73. Temporal?
    Refers to all time, transmit(pulse duration) and revieve
  74. Pulsed?
    Refers to only to the trnasmit time only(pulse duration).
  75. SPTA
    Intensity that is most revelant to tissue heating.
  76. Attenuates?
    As sound travels in the body it weakens(attenuates
  77. Decibel notation?
    Is used to report chnges of attenuation
  78. Logarithms
    A method of rating numbers. Log represents the number of 10's that are multiplied to create the origional number
  79. 3db'S?
    Means the intensity was doubled its origional value
  80. 10db's?
    Means the intensity has become ten times larger than its origional value.
  81. -3db's?
    Means the intensity has become half its origional value.
  82. -10db's?
    Means the intensity has become 1/10 its origional value.
  83. Attenuation?
    The decrease in intensity, power, and amplitude as sound travels .
  84. Attenuation is determined by?
    Path legnth and frequency of sound.
  85. Attenuation coefficient?
    The number of decibels of attenuation that occurs when sound travels one centimeter
  86. Units of attenuation coefficent?
  87. Total attenuation is calculated by?
    attenuation coeffieient(db/cm) x distance(cm)
  88. Attenuation coefficient is?
    one half of the frequency.
  89. Half value thickness?
    Is the distance that sound travels in a tissue that reduced the intensity of sound to one half its origional value
  90. Units of half-value layer
  91. Half value thickness depends on?
    the medium, the frequency of sound
  92. Impedance
    is the acoustic resistance to sound traveling in a medium
  93. Impedance='s?
    density(kg/m^3 x prop. speed (m/s)
  94. Units of impedance?
    rayls, Z
  95. Impadance is determined by?
    Medium only.
  96. 4 Angles?
    acute(less than 90degrees), right(90degrees),obtuse(greater than 90 degrees), oblique(any other than 90degrees
  97. Two conditions for refraction?
    oblique incidance and propogation speeds of the two media are different.
  98. Go return time(time of flight)?
    The elapsed time from pulse creation to pulse reception
  99. Time of flight is directly related to?
  100. 13microsecond rule
    for every 13us of go return time, the object creating the reflection is 1 centimeter deeper ins oft tissue. ez 13us has a depth of 1 cm and the total distance traveled would be 2cm
  101. PRP='s?
    Imaging depth(cm) x 13us/cm.
  102. Axial resolution?
    describes the measure of detail in a image
  103. Piezoelectrice effect?
    describes the property of certain materials to create a voltage when they are mechanically deformed