Physics Boards Review Part 2

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dorkfork
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288519
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Physics Boards Review Part 2
Updated:
2014-11-07 16:24:13
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physics ultrasound doppler
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part 2
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  1. Which of the following parameters directly relates to heating of tissues?
    • Increase thermal index
    • Increased frequency or output power
  2. Which of the following rod groups scanned from side A would evaluate axial resolution?
    Rod group B
  3. What factors would produce the greatest TI values?
    • High frequency
    • Narrow focal zone
    • Stationary color doppler
  4. What factors would produce the greatest MI values?
    Low frequency, high intensity
  5. The artifact indicated by the arrow is due to:
    • Reverberation/ comet tail
    • Large acoustic impedance missmatch
  6. Which system control manipulations would best limit patient exposure to ultrasound energy?
    • Decrease scan time
    • M-mode vs. color doppler or pulsed wave
    • Decrease frequency
  7. A transducer has a very wide slice thickness. This may produce:
    • Filling defect of a cystic/anechoic structure
    • Filling in of vessels / small cyts
  8. Which of the following produces the split image artifact?
    • fat/muscle interface near the surface
    • i.e. linea alba
  9. Which of the following types of tissue will demonstrate the greatest temperature elevation?
    • embryo <8 weeks conception
    • head, brain, and spine of any fetus or neonate
    • eye in any patient
  10. Which of the following digital scan converters would display the best contrast resolution?
    • 8 bit
    • 8 is the current standard
    • 2= shades of gray, where n = bits in a computer word
  11. Bioeffects have been observed in experimental animals with focused intensities greater than:
    1 W/cm2
  12. On an A-Mode display, the height of the spike represents:
    The echo intensity
  13. The System Gain function is performed in the:
    Beam former
  14. What is the maximum number of displayed shades of gray in a 6-bit processor?
    2= 64
  15. What determines the power of the ultrasound field?
    Voltage applied to the transducer
  16. The typical pulse repetition frequency range for clinical imaging applications is:
    • Low range
    • 10-20kHz
  17. The term signal to noise ratio is:
    The ratio of signal amplitude to the variation in noise
  18. In cardiac imaging, reducing the size of the sector angle will:
    Increase the frame rate
  19. If the imaging depth is quartered, the frame rate will be:
    Quadrupled
  20. The signal processing function that eliminates the negative component of the signal is termed:
    Rectification
  21. Adjusting the TGC controls affects the settings in the:
    Beam former
  22. The ability to distinguish between adjacent structures producing similar echo amplitudes is termed:
    Contrast resolution
  23. When the pulse repetition period is increased:
    Imaging depth is decreased
  24. If the gain is increased by 6 dB, the power has been increased by a factor of:
    4
  25. When comparing Write magnification with Read magnification, Write magnification:
    Improves spatial resolution compared to read magnification
  26. During real time imaging, if the scan line density is reduced to 1/2, the maximum frame rate is:
    Doubled
  27. Preprocessing programs are performed in the:
    Image processor
  28. If the original acoustic power is 100 mW and the power control is increased by 3 dB, the new power is _____ mW.
    200
  29. In real time systems, the range equation is used to determine reflector:
    Depth
  30. The typical dynamic range in the amplifier is:
    60-100
  31. The sonographer has increased the size of the sector width to image a large mass. What can the sonographer do to maintain the same temporal resolution before this adjustment?
    Decrease the number of focal zones.
  32. Increasing the pulse repetition frequency will:
    Decrease the maximum imaging depth
  33. Reflector B is twice the distance from the transducer as reflector A. It takes ______ times as long for an echo to arrive from reflector B as from reflector A.
    2
  34. The computer parameter that limits the number of brightness levels available to display on the image matrix is:
    Number of bits in computer word
  35. The primary method that the sonographer uses to control frame rate during real time imaging is:
    Imaging depth
  36. Which mode has time the unit of measurement on one axis?
    M-mode
  37. Flow through a blood vessel is determined by:
    • 1. Pressure difference
    • 2. Vascular resistance
  38. Vessel diameter increase as _____ increases.
    Pressure
  39. Veins or arteries, which are more distensible?
    Veins are 6-10 x as distensible as arteries
  40. Arteries
    • Transport blood to tissues
    • High pressure
  41. Arterioles
    • Last, smallest branches of the arterial system
    • Act as "control valves" for blood flow into capillaries
  42. Capillaries
    Exchange between blood and interstital spaces
  43. Vasodilitation occurs when?
    • During exercise
    • After a meal
  44. Vasoconstriction occurs when?
    • In a resting state
    • With fasting
  45. Venules
    Collect blood from capillaries and connect to larger veins
  46. Veins
    • Blood returned to heart
    • Body contians many more veins than all other parts of the vascular system
  47. AO/ICV
    Have the smallest cross-section area and therefore the highest velocity
  48. Relationship of velocity to area
    Velocity is inverse to area
  49. Energy derived from the cardiac pump
    Potential/pressure energy
  50. Potential energy
    • Pressure/stored energy
    • Derived from the cardiac pump
    • Distends vessels and stores energy
  51. Kinetic energy
    • Energy of motion
    • KE < PE due to distensibility of vessels
  52. Kinetic energy can increase due to:
    • Increase in flow>> i.e. exercise
    • Stenosis (increased velocity)
  53. Movement of fluid between 2 points requires:
    • Difference in energy
    • Difference in pressure
  54. Example of low resistance
    • Organs
    • Low resistance = greater energy difference = greater flow
  55. Example of high resistance
    • Resting muscle
    • High resistance = less flow
  56. Pouseuille's law
    Defines relationship between pressure, volume flow, and resistance
  57. The longer the vessel the _____ the resistance.
    • Higher
    • High pressure is required to maintain flow
  58. The shorter the vessel the ____ the flow volume.
    Higher
  59. What has the most significant impact on flow rate?
    • Radius of the vessel
    • Smaller the radius, the higher the resistance
  60. Smaller the radius, the _____ the resistance.
    Higher (and higher pressure)
  61. Plug flow
    • Flat profile
    • Seen in stenotic area
    • Same velocity throughout vessel (slower flow at wall)
  62. Laminar flow
    • Most common flow pattern
    • Seen during systole in smaller arteries
    • Flow in center is highest and gradually tapers as it reaches the wall of the vessel
  63. Disturbed flow is signified by?
    Spectral broadening
  64. Mathematical number to determine when flow turbulence will occur?
    Reynold's number
  65. Reynolds number for when turbulance will occur
    2000 Re or higher
  66. Harmonic resonance produced by flow turbulence transmitted into vessel walls is known as
    audible bruit
  67. Where is normal disturbed flow visualized throughout the cardiac cycle?
    • Bifurcations
    • Curves
  68. Significant stenosis
    70% blockage
  69. Tardus parvus
    Dampened wave forn distal to a stenosis
  70. Monophasic flow
    • Low resistance, continuous and steady throughout S and D
    • Seen in normal arteries that supply low resistance vascular beds -liver, spleen, brain, kidneys
  71. Triphasic flow
    • Highest resistance to flow
    • Antegrade/forward flow during systole
    • Retrograde/reverse flow during diastole
    • Seen in distal AO/iliac arteries
  72. Cosine of the doppler angle is ______ly related to the doppler angle.
    • Inversely related
    • Angle of 0 = cosine 1.00
    • Angle of 90 = cosine 0
  73. Increase transmit frequency and _____ the size of the Doppler shift
    Increase
  74. Decrease velocity of flow and _____ the size of the Doppler shift.
    Decrease
  75. Increase the Doppler angle and _____ the size of the Doppler shift.
    Decrease
  76. Decrease the Doppler angle and ______ the size of the Doppler shift.
    Increase
  77. Cosine = 0
    • 90 degree angle
    • No Doppler shift
  78. Cosine = 1.00
    • 0 degree angle
    • Largest Doppler shift
  79. With spectral analysis the frequency is displayed on which axis?
    Vertical y axis
  80. What is displayed on the X axis of spectral analysis?
    Time
  81. Amplitude or power is displayed as what on spectral analysis?
    Brightness
  82. FFT
    • Fast fourier time
    • Current computer program for analyzing and displaying spectral representation
  83. How can aliasing be eliminated?
    • Increase PRF (increased nyquist limit)
    • Shift baseline
    • Increase size of angle
    • Decrease transmit frequency
  84. Main disadvantage of pulsed Doppler is?
    Aliasing
  85. Nyquist Limit
    • 1/2 the PRF
    • Exceeding this produces aliasing
  86. PRF control
    Changed the number of pulsed emitted per second
  87. Primary advantage of CW Doppler
    No velocity limit/ no aliasing
  88. Main disadvantage of CW Doppler
    • Large fixed sample volume
    • POOR RANGE RESOLUTION
  89. Color Doppler
    • Qualitative, NOT quantitative information
    • Will produce aliasing
    • Good range resolution
    • BART
  90. How to eliminate color aliasing
    • Increase PRF (scale setting)
    • Decrease sample volume depth
    • Use larger Doppler angle
    • Lower transmit frequency
    • Go from triplex(color, image, spectra) to duplex (color, image)
  91. Power Doppler
    • Encodes amplitude of blood cells
    • Provides no info on direction of flow
    • NO aliasing and less angle dependant
  92. Components of pulsed Doppler instrumentation:
    • Pulser
    • Gated detector
    • Spectral analysis
    • Memory
    • Display
    • Speakers
  93. Length of pulses produced by pulser
    5-30 cycles
  94. The time period for acquisition of Doppler signal is determined by the _____.
    Size of the gate
  95. Phase shift means
    Motion is present
  96. Rhythmic cycles or beats produced when waves of different frequencies produce interference are added together and termed
    Beat frequency
  97. Minimum number of cycles per pulse is?
    4
  98. Number of cycles required for fast flow
    6-10
  99. Number of cycles needed for gray scale
    2-3 cycles
  100. Number of cycles needed for slow flow
    20-30
  101. Typical sampling rate
    25,600 times per second
  102. High pass filter
    • Rejects all frequencies below the threshold vaule
    • Usually 100Hz
    • Removes wall thump but not slow flow
  103. Low pass filter
    • Eliminates high frequency noise
    • Improper adjustment can eliminate high frequency (fast) flow
  104. One speed estimate has a _____  pulse minimum.
    Three
  105. More than 3 pulses are required in order to:
    • Improve accuracy of the estimate
    • Determine the variance
    • Improve detection of slow flow
  106. Typical ensemble length range
    10-20 pulse
  107. Increasing ensemble length will ___ frame rate.
    Decrease
  108. Ensemble length
    • AKA pulse packet size
    • The number of pulses required to produce one color scan line
  109. Transient cavitation refers to :
    • AKA collapse cavitation or normal cavitation
    • Bubble oscillation so large that the bubble collapses
  110. No thermal effects have been documented when the temperature elevation is below ___ degrees.
    2
  111. A Thermal Index (TI) value of one (1) indicates:
    Potential to increase tissue temperature by 1 degree
  112. The artifact indicated by the white line can be eliminated by:
    Aliasing
  113. Which mode has the potential for the highest thermal production?
    Color doppler
  114. A device commonly used to measure the output of diagnostic ultrasound systems is:
    Hydrophone
  115. A tumor has a slower propagation speed than the soft tissue average propagation speed. This will result in:
    Shadowing
  116. A long near zone can be obtained by:
    Increase frequency (decrease λ)
  117. Higher the ____ the shorter the SPL
    Frequency
  118. Shorter the SPL the better the ____ resolution
    axial
  119. SPL=
    • SPL= λ x # of cycles in pulse
    • Shorter the SPL the better the axial resolution
    • Higher the frequency the shorter the SPL
  120. Longitudinal or axial resolution is directly dependent on:
    • Spatial pulse length
    • SPL= λ x # of cycles in pulse
    • Shorter the SPL the better the axial resolution
    • Higher the frequency the shorter the SPL
  121. Generally, ultrasound transducers have better _____ resolution than ________ resolution.
    Better axial resolution than lateral resolution
  122. Which equipment assumption is violated when refracted echo information is processed?
    All echoes come from straight ahead
  123. To reduce the Mechanical Index (MI), the sonographer would:
    Decrease acoustic power, increase the number of focal zones
  124. Mechanism through which ultrasound energy can produce a biological effect
    Stable caviatation, transient cavitation, increase in temperature
  125. The artifact indicated by " A" is indicates:
    Large acoustic impedance missmatch
  126. If the focal zone is decreased to 1/5 of its original area, the intensity will:
    Increase by 5
  127. Which rod groups scanned from side C would evaluate lateral resolution?
    Rod group C
  128. Side lobe artifact produces which of the following sonographic characteristics?
    • Energy distribution outside main beam profile
    • Horizontal linear extensions from specular reflector (i.e. septa)
  129. The risk of cavitation is considered low when the MI value is ____ or lower.
    0.5
  130. PhThe area of the sound field characterized by violent intensity changes is:
    Near field

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