Unit 5 (Fluoroscopy)

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  1.  who invented fluoroscopy and when?
    • Thomas Edison
    • 1896
  2. name some basic components of the image receptor of the earliest fluoroscopy unit:
    • fluoroscopic screen
    • mirrors
    • image intensification
    • video camera and monitor
  3. name two functional studies that utilize fluoroscopy:
    • GI tract studies
    • angiograms
  4. describe our ethical guidelines when it comes to using fluoroscopy for patient positioning:
    the unneccessary radiation exposure caused by using fluoro for positioning is unethical because technologists have been trained in positioning.
  5. what is the mA range in fluoroscopic x-ray tubes?
    .5 to 5.0 mA
  6. what is the minimum SOD in fixed fluoroscopic equipment?
    15"
  7. describe viewing early fluoroscopic screens:
    • very dim
    • required "dark adapted" viewing
    • low visual acuity
    • uses scotopic vision (rods)
  8. the rods of the eyse utilize _________ vision, and the cones of the eyes utilize _________ vision.
    • scotopic
    • photopic
  9. when was the image intensifier first introduced, and what did it offer?
    • 1948
    • higher visual acuity
    • uses photopic vision (cones)
  10. use the labeling of this picture to describe what happens in the image intensifier:
    • A. entrance x-ray photon
    • B. light photons: converted from the x-ray photons after passing through input fluorescent screen
    • C. photocathode and input fluorescent screen: where conversions take place
    • D. photoelectrons: converted from light photons after passing through photocathode
    • E. electron stream
    • F. electrostatic lenses: negatively charged, therefore pushing electrons toward center as they travel
    • G. glass house
    • H. anode: positively charged point where electrons are drawn. electron stream is flipped when passing through (focal spot)
    • I. output fluorescent screen: converts electrons back to light
    • J. exiting light photons
  11. what is the main function of the image intensifier?
    to reduce patient dose by amplification
  12. what is another name for the fluorescent screen?
    phosphor screen
  13. how do you determine the total brightness gain?
    minification screen x flux gain = total brightness gain
  14. what is the input screen of the image intensifier composed of and what is its function?
    • .1 to .2 mm layer of sodium activated CsI (cesium iodide)
    • converts intercepted x-ray beam to light
  15. what is the function of the photocathode of the image intensifier?
    emits electrons when struck by light photons emitted by input screen
  16. what is the function of the electrostatic lenses in the image intensifier?
    they accelerate and focus the electron pattern across the tube to the anode
  17. what is the primary source of brightness gain?
    the electrostatic lenses
  18. what is the function of the magnification tubes of the image intensifier?
    they give greater voltage to the electrostatic lenses which allows them to increase the acceleration of electrons and shift the focal point away from the anode
  19. the smaller the area of the input screen, the _______________ magnification on the output screen.
    greater
  20. what is a dual focus magnification tube?
    • offers more than one size area that can be interacted with
    • ex. 23/15
  21. describe the anode of the image intensifier:
    it is positively charged, 25kVp, with a hole in the center that allows electrons to pass through to the output screen
  22. where does the cross-over point of the focal spot take place?
    at the anode (unless magnification pushes it toward the input screen)
  23. what is the output screen of the image intensifier composed of and what is its function?
    • glass fluorescent screen composed of zinc-cadmium sulfide
    • emits light when struck by electrons
  24. how do you determine minification gain?
    minification gain = (input screen diameter2)/(output screen diameter2)
  25. in determining minification gain, what are the general ranges of screen diameters?
    • input screen ranges from 15 to 30 cm
    • output screen is around 2.5 cm
    • therefore, the big number will always be on top when determining minification gain
  26. the measurement of conversion efficiency of the output screen:
    flux gain
  27. give an example of how flux gain is determined:
    if one electron strikes the output screen and 50 light photons are emitted, then the flux gain is 50.
  28. what is a modern term used to represent an increase in brightness, or brightness gain?
    conversion factor
  29. who recommend the use of the conversion factor to quantify the increase in brightness created by an image intensifier?
    the ICRU (International Commission of Radiation Units and Measurements)
  30. pay attention to slide number 27 of the power point as an example for working formulas to calculate minification gain and total brightness gain.
    : )
  31. an expression of the ability of an image intensifier to convert x-ray energy  into light energy and increase brightness in the process:
    brightness gain (now called conversion factor)
  32. an expression of the luminance at the output phosphor divided by the input exposure rate:
    conversion factor (formerly called the brightness gain)
  33. as the tube ages the exposure rate ___________. therefore, the exposure rate needs to be ____________ to maintain brightness.
    • decreases
    • increased
  34. how do you determine the conversion factor?
    conversion factor = luminance at output phosphor / input exposure rate
  35. what is the unit of measurement in figuring the conversion factor?
    • candela per square meter per milliroentgen per second
    • (cd/m2/mR/s)
  36. the numeric version of the conversion factor is approximately ________ of the brightness gain value.
    1%
  37. the higher the conversion factor or brightness gain value, the _________ the efficiency of the image intensifier.
    greater
  38. what is ABC and what does it do?
    • automatic brightness control
    • makes automatic adjustments to equipment exposure factors
    • maintains contrast and density by adjusting kVp and/or mA
  39. ›amplifies video signal rather than adjusting exposure factors:
    automatic gain control
  40. what is the difference between automatic gain control and automatic brightness control?
    • automatic gain control amplifies video signal
    • automatic brightness control (ABC) adjusts exposure factors
  41. name four main factors that affect image quality:
    • contrast
    • resolution
    • distortion
    • quantom mottle
  42. in fluoroscopy, what is contrast controlled by and what is it affected by?
    • controlled by amplitude of video signal
    • affected by scattered ionizing radiation and penumbral light scatter
  43. in fluoroscopy, the resolution of video viewing is limited by:
    the 525 line raster pattern of the monitor
  44. how do raster patterns affect resolution?
    the greater the number of lines in the raster pattern, the greater the resolution of the video signal
  45. what is the primary cause of size distortion and how can it be combated?
    • OID
    • combated by bringing image intensifier as close to patient as possible (thereby decreasing OID)
  46. name two common shape distortions caused by the shape of the input screen:
    • vignetting
    • pin cushion effect
  47. ____________ shape of the input screen helps to minimize _________________, but does not remove it all.
    • concave
    • shape distortion
  48. what is quantom motte, its cause, and how it is most commonly remedied?
    • blotchy, grainy appearance
    • caused by too little exposure
    • remedied by increasing mA
  49. name two types of video viewing systems:
    • closed circuit television
    • video camera tube
  50. a video viewing system in which there is a video camera coupled to an output screen and monitor:
    closed circuit television
  51. two types of video viewing systems in which a video camera tube is used:
    • Vidicon or Plumbicon tube
    • CCD
  52. how are Vidicon and Plumbicon tubes different?
    • they have different target materials
    • Plumbicon has a faster response time than Vidicon
  53. in video camera tubes, there is a __________ signal going in, and a __________ signal going out.
    • electrical
    • video
  54. in a video camera tube, the cathode is the:
    control grid
    • A. cathode
    • B. control grid
    • C. focusing coil
    • D. deflecting coil
    • E. electron beam
    • F. glass face plate
    • G. signal plate
    • H. target
    • I. video signal
    • J. anode
  56. name three parts that make up the anode of the video camera tube:
    • face plate
    • signal plate
    • target
  57. name two parts of the cathode of the video camera tube and their functions:
    • heating assembly: has an electron gun that controls thermionic emission
    • control grid: shapes the electron beam
  58. describe the target of the video camera tube:
    • a thin insulating mica
    • a matrix of globules of photoconductive material
  59. give the target materials of the two video camera tube types:
    • Vidicon: antimony trisulfide
    • Plumbicon: lead oxide (faster)
  60. what is the function of the raster pattern?
    accelerates the electron beam across the TV camera tube to the anode
  61. what slows the raster pattern at the anode?
    wire mesh in front of the target
  62. in the video camera tube, shapes the electron stream into a single point:
    electromagnetic focusing coils
  63. in the video camera tube, causes the electron stream to scan the  target in the raster pattern:
    deflecting coils
  64. name two components of the video camera tube that contribute to the formation of the raster pattern:
    • electromagnetic focusing coils
    • deflecting coils
  65. in the video camera tube, a positively charged thin film of graphite:
    the signal plate of the anode
  66. what is the function of the anode target in the video camera tube?
    it changes the light pattern to the electronic signal that is sent to the video system
  67. list the forms of energy as they travel through the cathode ray tube:
    from electrical, to electron, to light (which will be viewed at the monitor)
    • A. iron trap
    • B. electron gun
    • C. control grid
    • D. focus coil
    • E. deflecting coil
    • F. electron beam
    • G. anode
    • H. fluorescent screen
    • I. light photons
  69. a semiconducting device that emits electrons in proportion to the amount of light striking the photoelectric cathode:
    video camera charged coupled device (CCD)
  70. what does the CCD's fast discharge achieve?
    it eliminates lag
  71. name two advantages of the CCD over the video tube:
    • it operates at lower voltages
    • it is more durable
  72. here are the notes i jotted down in class from the youtube video on CCDs we watched from the powerpoint. decipher and go over them at your own risk!!
    • CCDs made of silicon
    • the human eye is more sensitive to green light (closer to middle of light spectrum) 
    • x-ray interacts, receptor receives the interaction, CCD receives it. With every x-ray interaction, releases negative charge (electrons)…capacitors in CCDs get more intensity (like from tissues, ligaments, etc), stores charge, then you’ve got the whole grid of reception with the CCD (the whole finished picture).
    • the areas with greater electrical charge have greater intensity. we want it to be changed to a digital form so we can see it.
  73. in digital fluoroscopy, the image intensifier output screen is coupled to:
    TFTs (thin film transistors)
  74. in digital fluoroscopy, TFT photodiodes are connected to:
    each pixel element
  75. in digital fluoroscopy, resolution is limited out of concerns for
    radiation exposure
  76. TFTs improve ___________________ and are used to display images on _______________.
    • image quality/contrast
    • an LCD screen
  77. name four ways of recording the fluoroscopic image:
    • dynamic systems
    • cine film systems
    • videotape recording
    • static spot filming systems
  78. when recording the fluoroscopic image, what is a film size of note in digital fluoroscopy?
    105mm chip film
  79. name two types of dynamic systems used in recording the fluoroscopic image:
    • cine film
    • videotape
  80. give measurements and rates specific to cine film systems for when the movie camera intercepts the image:
    • 16mm and 35mm formats
    • records series of static exposures at high speeds
    • 30-60 frames per second
  81. what do cine film systems offer as compared to dynamic systems?
    increased resolution (at the cost of increased patient dose)
  82. list some common advantages and disadvantages of videotape recording:
    • (VHS and VHS-S)
    • often used today with the speech pathologist
    • allows playback in real-time after the procedure
    • limited storage space is a disadvantage
  83. in static spot filming systems, what changes in mA are necessary in comparing fluoro and radiography modes?
    • fluoro mode: 2 to 5 mA
    • radiography mode: 100 to 1200 mA
  84. in static spot filming systems, which mode increases the dose to the patient and personnel in the fluoroscopy room?
    radiographic mode increases dose as compared to fluoro mode
  85. where is the film located in static spot filming systems?
    stored in a lead compartment until an exposure is ready to be made
  86. in static spot filming systems, what size film is utilized, and how can it be divided for exposures?
    • 9x9 film size
    • divides into 1 on 1; 2 on 1; 4 on 1; and 6 on 1
  87. in static spot filming, what allows the film to be exposed photographically?
    a beam-splitting mirror during the exposure
  88. in static spot filming, since the process is photographic, how must it be developed?
    in a wet processor in a darkroom
  89. in static spot filming, how many frames per second can be taken?
    up to 12 frames per second
  90. taking an image using the image intensifier causes _________ dose to the patient as compared to the spot film.
    less
  91. describe digital fluoroscopy with the use of a CCD:
    • uses the CCD to generate an electrical signal
    • the signal is sent to an ADC
    • allows for post processing and electronic storage and distribution
  92. name the three pillars of radiation protection and who they are meant to protect
    • time, distance, shielding
    • patient, radiologists and technologists, others
  93. in patient protection, list the minimum SSDs (source to skin distances) for both mobile and stationary equipment:
    • mobile equipment: 12" minimum SSD
    • stationary equipment: 15" minimum SSD
  94. for patient protection, when do audible alarms sound in the use of fluoroscopy?
    at 5 minutes
  95. what is the maximum exposure rate of the x-ray beam at tabletop that is deemed acceptable by the FDA?
    • maximum of 10 R/min: for units with automatic brightness stabilization (ABS)
    • maximum of 5 R/min: for units without automatic brightness stabilization (ABS)
    • (typically 1-3 R/min is used)
  96. give typical exposure rates for cinefluoroscopy, cassettes, and 105 mm film:
    • cinefluoroscopy: 7.2 R/min
    • cassettes: 30 mR/exposure
    • 105 mm film: 10 mR/exposure
  97. the minimum required shielding required for lead gloves and thyroid shields:
    .25 mm  lead equivalency(by the NCRP No. 102)
  98. the minimum required shielding required for lead aprons:
    .5 mm lead equivalency (by the NCRP No. 102)
  99. describe the angle and level of most scatter radiation in the fluoro room:
    • ›90° angle to the incident beam
    • the level of the radiologist's/technologist's gonad area
  100. the minumum required shielding for the primary barrier of the fluoro tower's image intensifier:
    2.0mm of lead equivalency (by the FDA)
  101. the minimum required shielding for the protective curtain:
    .25 mm lead equivalency (by the NCRP No. 102)
  102. the minimum required shielding for the bucky slot cover:
    .5 mm lead (Pb) equivalency

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Author:
 nenyabrooke
ID:
 185110
Filename:
 Unit 5 (Fluoroscopy)
Updated:
2012-11-26 01:10:23
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Physics
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Unit 5 (Fluoroscopy)
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