Physics Boards Final Reveiw

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Physics Boards Final Reveiw
2014-11-27 23:02:50
Physics Ultrasound ARDMS

Physics Final reveiw
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  1. A decreased pulse duration produces:
    • Better axial resolution
    • decreased PD; increased listening time; increased frequency; decreased wavelength; decreased SPL; wider bandwidth
  2. The source of the acoustic enhancement artifact is:
    Due to a structure with a low attenuation rate
  3. Wavelength is determined by the:
    Sound source
  4. The technique used in most color Doppler systems used to obtain the mean Doppler frequency shift is:
    Fast Fourier transform/ spectral analysis
  5. The term signal to noise ratio describes:
    • Comparison of reflector signal in image to amount of contamination (noise)
    • High ratio = good (increased contrast resolution)
  6. The typical dynamic range in the amplifier is:
  7. Decreasing the wavelength improves:
    • Axial resolution
    • decreased wavelength; increased frequency; decreased SPL; wider bandwidth; decreased PD; increased listening time
  8. As tube radius increases, resistance:
  9. As frequency increases, half intensity depth:
  10. A large amplitude pulse (voltage) from the pulser results in:
    Increased frequency
  11. If the sample volume depth is doubled, the Nyquist limit will be ____ of the original.
    • 1/2
    • Nyquist =1/2 PRF
    • Increase maximum imaging depth attainable x 2 > decrease PRF x 2 > decrease nyquist limit in half
  12. What will improve detection of slow flow?
    • Low PRF / scale control
    • Increase color gain
    • Increase pulse packet size
    • Decrease Doppler angle
  13. The effect on the ultrasound image when the dynamic range is increased is:
    • Increase in the # of shades of grey
    • Low contrast image
  14. Heating of soft tissue is proportional to:
    Intensity of ultrasound energy and exposure time
  15. In color Doppler, the ensemble length controls the number of:
    Pulses required to produce one scan line of color information (3 pulse minimum)
  16. What is the maximum number of displayed shades of gray in a 7-bit processor?
    • 148
    • 27=148
  17. Advantages for increasing color ensemble length:
    • Improve the accuracy of the estimate
    • Determine the variance (turbulence)
    • Improved detection of slow flow
  18. Huygen's Principle describes:
    Constructive interference produces the typical hour glass shape of the sound feild
  19. Which of the following scanned from the top would evaluate the dead zone?
  20. The initial amplitude is determined by :
    Acoustic power control/voltage applied to the transducer
  21. Which of the following best describes apodization?
    • Method to control sidelobes
    • The use of variable strength voltage pulses to the crystal during focusing
  22. Propagation speed is determined by the:
    • Medium
    • Propagation speed =density x velocity
  23. As fluid viscosity increases, flow rate will:
  24. The source of the artifact indicated by the yellow arrow is:
  25. What effect will increasing the voltage delivered to the transducer have on amplitude?
    Increase the amplitude
  26. Which of the following displays the lowest intensity value in pulsed-wave ultrasound?
  27. When comparing Write magnification with Read magnification, Write magnification:
    • Write magnification magnifies the image before the image is stored
    • Better image resolution due to smaller pixel size
  28. The impedance of the matching layer is:
    In between that of the crystal (solid) and the coupling gel (liquid)
  29. What determines the power of the ultrasound field?
    Voltage applied to the crystal element (acoustic power control)
  30. When all other parameters are held constant, tripling the reflector velocity will result in:
    3 x the acoustic impedance value (z)
  31. The cause of this artifact (double aorta - white lines) is:
  32. The resonant frequency of the ultrasound pulse is determined by:
    Crystal thickness
  33. Which of the following system components generates the signals to focus and steer the sound field?
    Beam former
  34. When the pulse repetition period is increased:
    • PRF decreases
    • Increase PRP > decrease PRF > increase imaging depth > decrease frequency > increase wavelength
  35. Which Doppler technique has poor range resolution?
    Continuous wave doppler
  36. Propagation speed error results in which of the following sonographic characteristics?
    Improper reflector position due to increased RTT
  37. The use of contrast agents in sonography:
    Has not been approved for use in the states
  38. Which intensity is the greatest during the pulse?
    Intensity in the focal zone
  39. Pulse echo imaging typically employs a duty factor of ___ percent?
  40. At a soft tissue/air interface, the percentage of sound transmitted will be:
  41. In clinical applications, maximum reflection amplitude occurs with:
    Normal incidence
  42. The type of real-time system that employs a combination of electronic focusing and mechanical steering is:
  43. Spectral analysis is used to:
    • Display quantitative info from pulsed doppler
    • X axis: frequency shift
    • Y axis: time
  44. The best example of a Rayleigh scatterer is:
    Red blood cells
  45. A transducer has a very wide slice thickness. This may produce:
    Averaging of peripheral and central echoes (slice thickness artifact)
  46. Which of the following scanned from the top would evaluate axial resolution?
  47. Increasing the pulse repetition frequency will:
    • Decrease the maximum imaging depth
    • Increase PRF, decrease PRP, decrease max imaging depth
  48. The computer parameter that limits the number of brightness levels available to display on the image matrix is:
    # of bits in a word
  49. Temporal resolution is determined by:
    • Imaging depth
    • Sector width
    • # of focal zones
  50. Based on this delay sequence (black crystals on the left), the sound field will:
  51. The method for sterilizing transducers is:
  52. Increasing the number of scan lines per frame
    Increases detail resolution
  53. Widening of the sound field is demonstrated in the:
    Far feild/ Fraunhaufer zone
  54. A very narrow spectrum of frequencies under systole and diastole represents blood flow that is:
    Low resistance/ monophasic
  55. The minimum pulse packet size in color Doppler is:
    3 pulse minimum
  56. Mirror image artifact results in which of the following sonographic characteristics?
    Ghost image of real reflector is seen on opposite side of the "mirror"
  57. For focused ultrasound, there are no confirmed signicant biological effects in mammalian tissue for exposures below:
    1 W/cm2
  58. Impedance is equal to:
    • density x velocity
    • c x p
  59. As resistance increases, flow volume:
  60. The generation of the artifact displayed in this image (>) is due to:
  61. An increase in frequency will decrease all of the following EXCEPT:
    • Increase frequency
    • Decrease wavelength
    • Decrease SPL
    • Decrease PD
    • Increase axial resolution
  62. The approximate clinical frame rate (per second) for a real time image to be flicker-free is:
    ~15 per second
  63. Continuous wave transducers consist of:
    • CW = 2 transducers
    • Large fixed sample volume
    • Poor range resolution
    • No velocity limit (NO ALIASING!!)
  64. If the pulsed Doppler sample volume depth is decreased, the PRF will:
  65. Exceeding the Curie point of the element will result in:
    Destroying the crystals
  66. What conditions will result in aliasing of the Doppler frequency shift?
    • Exceeding the nyquist limit
    • Sampling at very deep imaging depths
  67. Side lobe artifact results in which of the following sonographic characteristics?
    • Energy distribution out side of main beam profile
    • Nonspecular example: hypoechoid sludge
    • Specular example: hyperechoic septa
  68. Which of the following body tissues will most likely increase acoustic speckle?
    Body tissues with higher attenuation rates (adipose tissue and muscle)
  69. If the transducer Q value is low, the bandwidth will be:
    Low Q = more damping material, shorter pulse, *wider bandwidth*, decreased wavelength, increased frequency, increased axial resolution
  70. The sonographer can change the initial intensity by manipulating:
    Acoustic power control
  71. What is the diameter of the sound field at one near-zone length when using a 6 mm, 2.5 MHz transducer?
  72. Continuous wave Doppler has a Duty Factor of ___ %.
  73. To maximize reflection from a specular reflector, the sonographer should strike the interface at ______ degrees.
    90 degrees
  74. The sonographer has overestimated the Doppler angle of incidence while using angle correction. This error will cause:
    Underestimation of velocity
  75. Cavitation is the result of:
    High intensity and low frequency
  76. When all other parameters are held constant, an increase in the Doppler angle will result in:
    Decrease the Doppler shift
  77. A sound field demonstrates the most uniform intensity in the:
    Focal zone
  78. Doppler shift information is determined by which type of reflector?
    Rayleigh scatter (RBCs)
  79. Determine the power if the amplitude of the wave is 4.
    Power = amplitude2

  80. Lateral resolution is determined by the:
    Beam width (focusing)
  81. Bandwidth can be increased by:
    Wide bandwidth, increased damping material, short pulse, higher frequency shorter wavelength
  82. What is the product of the number of cycles in the pulse and the pulse period?
    Pulse duration = period x # of cycles in a pulse
  83. Which of the following is most likely related to pixel density?
    Detail resolution
  84. A device commonly used to measure the output of diagnostic ultrasound systems is:
  85. Poor lateral resolution results in which of the following sonographic characteristics?
    Inability to distiguish reflectors located at the same depth (side by side) in the sound field
  86. Absorption of ultrasound energy is highest in:
  87. Which of the following varies with distance from the transducer?
  88. The pulse repetition period is the reciprocal of:
  89. Storage of several preceeding frames describes:
  90. Refraction is due to:
    • Oblique incidence
    • Velocity difference at an interface
  91. Which artifact is associated with reverberation and resonance in a small gas bubble or surgical staple?
    Comet tail
  92. As propagation speed and density values increase, acoustic impedance:
    • Increases
    • z = c x p
  93. The acoustic impedance of the damping material is:
    The same z value as the crystal
  94. Which Doppler angle produces the smallest error estimate?
    0 degrees/ cosine of 1.0
  95. The frame rate of a real time system does not depend on the:
    • Sector size/lines per frame
    • Depth
    • # of focal zones
  96. As frequency increases, the beam width will:
  97. Which transducer frequency in MHz would be best to use to avoid aliasing?
    Low frequency
  98. The signal processing function that eliminates the negative component of the signal is termed:
  99. Which artifact most frequently results in fill-in of small vessels or anechoic structures?
    Slice thickness artifact
  100. If the imaging depth is quartered, the frame rate will be: