Card Set Information

2011-04-21 20:36:11

Show Answers:

  1. What is a Cathode?
    Tube. Negative. Consists of the filament (usually 2; a large and small) encased by a focusing cup.
  2. What is AC Current? What does it produce?
    (Milliamperage is mA) (num. of electrons) heats the filament, causing a "boiling off" of electrons or "thermionic emission". This produces an electron cloud around the filament
  3. What happens when mA is increased?
    Increased temperature of the filament, and results in more electrons.
  4. What does a smaller filament provide?
    Better detail, sharper image, and les penumbra.
  5. What does a larger filament provide?
    Allows for more x-rays produced and better dissipation of heat. It is used for thicker objects.
  6. What is a high voltage (DC) current? What does it provide?
    kVp which is applied across the tube. This results in an electrical potential or "pressure" which drives the electrons towards the anode (positive) at a high speed.
  7. What does an increase in kVp result in?
    Faster electrons
  8. What interacts with the focal spot? Where is the focal spot located? What is the result?
    The high speed (or projectile) electrons interact with the focal spot of the anode target resulting in heat (99 percent) and x-rays.
  9. What are the two (electron-target) interactions that produce x-rays?
    Bremsstrahlung radiation and Characteristic radiation
  10. What is Bremsstrahlung radiation?
    "Braking". This radiation occurs when the projectile electron is deflected by the nucleus of a target atom.
  11. What is Characteristic radiation?
    A projectile electron ejects an inner shell electron of the target (anode). When an outer shell electron drops from the inner shell (to replace the ejected electron), a high-energy radiation is produced. (This radiation is named since it is "characteristic" of the target element and orbit of the shell electron).
  12. How do x-rays exit the tube?
    X-rays exit the tube through te port (which has an inherent filtration of .5mm AL equiv.), the collimator (a positive Beam Limiting Device) and an added filtration (Al- aluminum)
  13. What do filters do?
    Filters "harden the beam" by absorbing "soft" (the low energy) x-rays. Filters mainly reduce skin dose but have no effect upon decreased scatter radiation.
  14. What is the purpose of a shield?
    Made out of (Pb-lead) are placed in front of, or on the patient and absorb all x-rays.
  15. What happens when the photons reach the subject?
    The xray photons that reach the subject either pass through to the film (remnant radiation) or are (partially or totally) absorbed. Since different tissues have different absorption rates, the remnant radiation (reaching the film) will result in different film densities. The absorbed photons cause ionization of tissue and scatter radiation (which may produce film fog).
  16. What are the important x-ray interactions with matter?
    Classic scattering, Compton scattering, Photoelectric
  17. What is Classic scattering?
    Aka "coherent" or "Thompson". A change in direction of a low energy photon mainly produces film fog and does not contribute to the radiographic image.
  18. What is Compton scattering?
    A medium energy photon ejects an outer shell electron (Compton energy) and scattered x-ray photon. This mainly results in scatter radiation and adversely affects the image.
  19. What is Photoelectric scattering?
    A low energy photon is absorbed by the subject but also produces a photoelectron. This is the main interaction involved in producing the latent image.
  20. What is a grid? What does a grid do?
    The grid which allows "remnant radiation" to pass through, but absorbs scatter radiation reducing film fog and increasing contrast.
  21. What is the Potter-Bucky diaphragm?
    The Potter-Bucky diaphragm moves the grid to "blur" the grid lines.
  22. What are grids made out of?
    Grids are composed of lead or aluminum strips.
  23. What is grid cleanup?
    The ability of grids to absorb scatter radiation and reduce film fog
  24. What is grid ratio?
    The grid ratio is the based on the height of the lead strips to the inner-space between. The higher the grid ratio the greater the "clean up".
  25. What is the "grid cutoff"?
    Grids require an increase in exposure to compensate for 1 degree radiation absorbed.
  26. What do xrays do to intensifying screens?
    Xrays reaching the cassette cause the intensifying screens to fluoresce and results in the exposure of the film.
  27. What are intensifying screens?
    Intensifying screens reduce patient exposure but result in loss of detail.
  28. What are faster screens?
    Faster screens have larger crystals but result in less detail.
  29. What is Milliamperes (mA)?
    Controls the temperature of the filament (the number of electrons), the quantity of xrays produced, and the film density.
  30. What percentage is needed to change mAs to produce a visible change on a film?
    30 percent
  31. How would you make a correction using mAs?
    To make a correction, mAs must be changed by a factor of 2 ( decreased to 50 percent, or increased to 200 percent).
  32. What does Time (S) determine?
    Time (S) determines the duration of the operation of the machine and subsequently, the quantity of xrays produced.
  33. What does Kilovolts (kVp) determine?
    Kilovolts (kVp) determines the quality of the xrays and film contrast by controlling the maximum current applied across the tube.
  34. What happens when kV is increased?
    Increasing kV (faster electrons) results in higher energy/ short wave length xrays with greater penetrability.
  35. What is film made out of?
    Silver halide crystals (Br, I) in a gel matrix (or emulsion).
  36. What is a safelight?
    15 watt bulb with a Wratten b (or GBX-2) filter.
  37. What is developer?
    The exposed silver halide crystals are reduced to black metallic silver, converting the "latent image" to a visible image.
  38. If you were to develop a film manually what do you need to know?
    Manual processing 60 degrees F for 5 minutes.
  39. What is a reducer/ developer?
    Produces shades of gray and black (phenidone or hydroquinone)
  40. What is an accelerator/ activator?
    Swelling of emulsion, produces alkalinity (sodium carbonate)
  41. What is a preservative?
    Controls oxidation ((sodium sulfite or potassium sulfite)
  42. What is a restrainer?
    "Protects" unexposed crystals (potassium bromide, potassium iodine)
  43. What is a hardener?
    Controls swelling of the emulsion (glutaraldehyde)
  44. How long do you rinse a film after the developer has been applied?
    30-45 seconds
  45. What is the fixer? How long is the fixer applied?
    10 minutes. Stops the developing process, removes unexposed silver halide crystals, and hardens the emulsion.
  46. What are the four steps when applying the fixer?
    Acidifier/ activator, clearing agent, hardener, and preservative
  47. What does the acidifier/ activator do?
    "Stop bath" neutralizes the developer (acetic acid)
  48. What does the clearing agent do?
    "hypo solution" removes undeveloped silver halide (ammonium thiosulfate or sodium thiosulfate)
  49. What does the hardener do?
    Stiffens and shrinks the emulsion ( potassium alum)
  50. What does the preservative do?
    Maintains pH of fixer (sodium sulfite)
  51. How long do you wash the film after the developer and fixer have been applied to the film?
    20 minutes.
  52. What happens to a film when it is ...DARK?
    Light leak, developer temperature too hot, overexposure
  53. What happens to a film when it is...LIGHT?
    Developer temperature too low, chemicals need replacing
  54. What happens when a film is ...BROWN?
    Inadequate developer
  55. What happens when a film is...MILKY?
    Inadequate fixer
  56. What happens to a film when it is...GREASY?
    Insufficient washing
  57. What happens to a film when it is...INCREASED FOG?
    Old film, hot developer, contaminated chemicals
  58. What happens to a film when it is...SOFT EMULSION?
    Insufficient fixing
  59. What are the 10 properties of X-Ray?
    Travels at the speed of light, travels in a straight line, no mass, no charge, ionizes matter, penetrates matter, affects film, causes screen fluorescence, cannot be focused with a lens, produces scatter radiation
  60. Def. Density (film)?
    The degree of overall film blackness. Density related to the quantity of xrays produced (mAs) and radiographic exposure.
  61. Def. Contrast (radiographic)?
    The gradient difference between various radiographic densities (black and white). A high contrast (short scale) image is very white and very black; a low contrast (long scale) image will show more shades of gray. Contrast is inversely related to kVp.
  62. What is the rule between kVp and contrast?
    Increase kV-decrease contrast (more gray). Decrease kV-increase contrast (more black and white).
  63. Def. Geometric factors?
    Includes focal spot size, Focal Film Distance (FFD), Object Film Distance (OFD), xray machine alignment, patient placement.
  64. Def. Distortion?
    The radiographic misrepresentation of the size or shape of an object.
  65. Def. Detail?
    The degree of film sharpness.
  66. How is detail improved?
    Detail is improved with: smaller focal spot, collimation, increased FFD, decreased OFD, grids, patient positioning and machine alignment, shorter exposure time.
  67. Def. Umbra?
    The primary xray shadow producing the radiographic image.
  68. Def. Penumbra?
    The area of unsharpness or fuzziness around the radiographic image. Penumbra is increased with a larger focal spot size, lack of collimation, decreased FFD, increased OFD.
  69. Def. Primary radiation?
    Xrays produced at the tube, aimed at the patient for the purpose of exposing the film (the useful beam).
  70. Def. Scatter radiation?
    A type of secondary radiation which is produced by an absorber.
  71. What does scatter radiation produce?
    Film fog
  72. Def. FFD?
    Focal Film Distance. AKA (TFD, SID, SFD). The distance between the focal spot and the film. Increase FFD as much as is practical to decrease magnification.
  73. Def. OFD?
    Object Film Distance. AKA (PFD). Always decrease as much as is practical to decrease magnification.
  74. Def. Inverse square law?
    "the intensity of the radiation varies inversely with the square of the distance". Doubling the distance (FFD), results in a decrease of intensity of the radiation to one-fourth, and requires a compensatory increase of the mAs by 4 times!
  75. Def. Anode heel effect?
    Due to the angle (bevel) of the anode target, the intensity of the xray beam INCREASES slowly toward the CATHODE; and DECREASES rapidly toward the ANODE.
  76. Def. Air gap technique?
    A method of reducing scatter radiation where the object is placed approximately 10-15cm from the film.
  77. What is the disadvantage to the air gap technique?
    Increases magnification
  78. Def. Rectification?
    The process of converting AC current to DC current
  79. Def. 15 percent rule?
    The effect of increased kVp by 15 percent (upon film density) is equivalent to doubling the mAs.
  80. Def. Compensation filter?
    Compensates for differences in radiographic density.
  81. Def. Wolff's Law?
    Bone deposition occurs along the lines of increased mechanical stress.
  82. Def. Hueter-Volkmann Law?
    Pressure ona growth plate retards the rate of growth, traction accelerates.
  83. Def. Half Value Layer?
    "HVL". The ticknes of a material needed to attenuate the xray intensity by 50 percent.
  84. Def. Law of Bergonie and Tribondeau?
    The radio-sensitivity is directly related to: younger, more undifferentiated cells, or tissue with high metabolic activity or proliferative rate. (Very radio-sensitive: lymphoid tissue, marrow, gonads. Radio-resistant: brain, spinal cord, muscle).
  85. Def. Roentgen?
    A unit of exposure to ionization radiation.
  86. What does REM stand for?
    Roentgen Equivalent in Man
  87. What does RAD stand for?
    Radiation Absorbed Dose
  88. What are the nine radiographic protection measures?
    Collimation, filtration, intensifying screens, high speed film, shielding, high kVp/low mAs, dosimetry, minimize retakes, 10 day rule.
  89. Why is collimation important in protection?
    Most important means of protection to the patient and operator. Collimation decreases the size of the beam, decreases exposure, scatter radiation and penumbra.
  90. What is dosimetry?
    Use of radiation detection devices, like badges)
  91. What are the most common reasons for retaking a film?
    Motion, darkroom/processing errors
  92. What is the 10 day rule?
    The safest period to take a (lumbo-pelvic) xray a female during child-bearing age is the 10 days following the onset of menses.
  93. What adjustments need to be made when taking a film of a patient with osteoporosis?
    Decrease kV by 6-10kV (females greater than 55 yoa, males greater than 60 yoa)
  94. What adjustments need to be made when taking a film of a patient that is very muscular?
    Increase kV by 6-10kV
  95. What adjustments need to be made when taking a film of a patient that is obese?
    Increase mAs 40-60 percent
  96. Radiographic positioning standards usually include 2 perpendicular views EXCEPT?
    Skull and mandible, wrist, hand, fingers, thumb, chest, sternum, clavicle, ribs, patella
  97. All views have a FFD of 40 inches EXCEPT?
    Non-AP cervical films, chest films, full spine.
  98. What is the rule of tilt?
    Adjust FFD for excessive tube tilt (decrease one inch per every 5 degree tube tilt)