RAD-171 Ch.7 & End of CH.6 X-Ray Production

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RAD-171 Ch.7 & End of CH.6 X-Ray Production
2013-09-28 15:20:10

x ray
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  1. how are x-ray photons created
    xray photons are created when high speed electrons from the cathode strike an anode target
  2. what is the speed of incoming electrons
    they travel from zero to half the speed of light in about 2 centimeters
  3. what is the incident electron
    it is the electron coming in from the filament
  4. what happens when incident electrons strike the target
    they convert their tremendous kinetic energy to the atoms of the target material

    this is the interaction that creates x-ray productions
  5. what is kVp
    • kvp is what pushes the electrons over to anode side the strength and power
    • which then produces greater stronger xray photons
  6. the greater the kVp of the incident electrons _______?
    the greater the quality (energy) and quantity (number) of photons created
  7. what is over 99% of the kinetic energy og the incident electrons is converted to what?
  8. what is the remaining 1 percent converted to from the incident electrons
    x-ray photons
  9. Heat is _____ rather than an ______?
    • excitation (creation of)
    • ionization (adding or removing an electron)
  10. what happens when more mAs is used?
    doubling the mAs does what?
    • more electrons come off the filament and thus more x-ray photons created
    • doubles amt of x-rays
  11. what technical factor is needed for the chest in order to get a clearer image
    of you need to more penetration of chest you need increase kVp
  12. what are the two types of target interactions that can produce diagnostic range x-ray photons
    • bremsstrahlung interactions
    • characteristic interactions
  13. what determines what interaction will occur?
    depends on the electron kinetic energy and the binding energy of the electron shells
  14. what is the bremsstrahlung interaction named by?
    the german word for braking or slowing
  15. what causes the incident electron to slow down and diverts the electrons course
    the force field
  16. what is the avg percentage of the x-ray beam that is diverted
  17. where do electrons slow down and lose energy
    at the force field nucleus
  18. what interaction is it when the kVp is under 70?
    and above 70?
    • bremsstrahlung
    • characteristic
  19. what atoms are the electrons absorbed in
    atom of tungsten
  20. What interactions deals with the exact difference between the entering and exiting kinetic energy of the electron
  21. can electrons that are leaving hit other electrons and create beam interactions
  22. the higher the kVP the higher the _____
    beam interaction
  23. what can a single electron cause??
    a single electron can cause numerous brems interaction in many different atoms before losing enough energy to became included in the current flow
  24. what happens when a characteristic electron occurs
    it only happens when the incident electron interacts with an inner shell electron
  25. how can an incident electron knock an inner shell electron from orbit, thereby ionizing the electron
    must have enough energy
  26. what remains in the inner shell when an electron has been knocked out of its orbit
  27. what does the hole do to the atom
    the atom becomes unstable
  28. so when the atom becomes unstable, does another electron replace it ?
    yes an electron from another shell will immediately drop into the hole
  29. what results in the energy difference between the two shells being emitted as an x-ray photon
    the dropping of an electron from an outer, higher energy state into an inner, lower energy state
  30. why are these emissions called characteristic photons
    b/c of their energy is exactly the difference between the binding energies of the outer and inner shells between which the electrons dropped
  31. explain the characteristic cascade
    once an outer shell electron has dropped to fill the hole another electron will drop to fill the hole it left and so on until only the outermost shell is missing an electron
  32. what process can produce numerous x-ray photons for each electron that leaves the atom
    characteristic cascade
  33. what electrons will produce characteristic photons used in diagnostic xray range
    electrons dropped in the k-shell
  34. how come photons from other shells are not used in diagnostic radiology
    their energies are too low to be significant
  35. List the heat unit rectification constants for the following:
    • single phase, full wave 1.00
    • three phase, 6 pulse 1.35
    • three phase, 12 pulse 1.41
    • high frequency 1.45
  36. what conditions are necessary for the production of xrays/
    the electrons hitting the target, you need a high vacuum, high voltage etc..
  37. what percentage of kinetic energy of the electrons is converted to x-ray photons? what happens to the rest?
    15 is actually produced as xrays the rest (99%) is heat
  38. what are the two target interactions that can product x-rays
    bremsstrahlung and characteristic
  39. what interaction is this

  40. what determines the nerfy of the photon produced during this interaction
    how close the electron gets to the nucleus forcefield, therefore how much it bends and how much energy is lost
  41. what determines the energy of the photons produces during the characteristic interaction
    the amt of energy lost from the outer shell to the inner shell (the jumping from hole to hole) 
  42. what is meant by the characterisitic interaction and cascade
    these interactions may occur only when the incident electron interacts with an inner shell electron

    characterisitic cascade happens when the actual process of jumping of on electron going into the next hole of the shell near it
  43. what is the k-shell binding energy for tungsten
    69.5 keV
  44. what is the relationship between the kilovoltage peak and the average energy of the photons in the orimary beam
    the avg of kev of the photons is 30-40% of the kVp
  45. what interaction occurs more often within the diagnostic range
  46. what is the kilovoltage peak
    • also it is the mx possible nergy for any photon that exits the xray tube
    • or the # we set up
  47. is the energy predictable in a characteristic interaction
  48. what is the binding energy
    it is when the electron is closer to the nucleus the stronger it is as it moves further away the more it has to work to hang on to the chain of other electrons
  49. why dont we use electrons in the other shells
    because they are weak
  50. which interactions are unprdicatble
  51. If a single incident electron can cause a variety of interactions in many different atoms before losing enough energy to become included in the current flow, what are most of these interacctions produced as?
  52. what is the emission spectrum
    it is when the x-ray photons are coming down all at once and have a plethora of different strengths like strong, weak, brems and characteristic photons
  53. when will characteristic electrons not comprise any of the useful beam
    • until the kVp is over 70
    • removal of the k shell requires keV of 69.5 from tungsten
  54. the farther away the electron was that dropped into anothe electrons position, the _______
    greater the energy imparted to the characteristic photon
  55. what is keV
    the measurement of a specific electron
  56. in a brems interaction if the incident electron is coming in at 90 keV, and hits a 10 keV electron what is the strength of it when it leaves
    80 keV
  57. what is the strength of an incident electron coming in at 100 keV when absorbed by tungsten atom exiting the orbit
    100 keV
  58. if the kVp is over 70, what is the percentage fo the primary beam that is brems and characteristic photons
    • 80-90% brems
    • 10-20% characteristic interactions
  59. what shell emissions are only used in diagnostic x-ray range
    k-shell the rest are abosrbed
  60. the __________ of the exposure is the maximum possible enrgy for any photon exiting the tube
    kilovoltage peak
  61. what happens when you change ma(quantity of electrons), mas, or time?
    results in a change of amplitude of the emission graph
  62. on the emission graph what phenomenon happens at around 69.5 keV
    it is burst or spike in the graph called and characteristic peak (Occurs when K-shell emissions reach their effective energy range of 69 keV)
  63. what do you do if you a change in the number of higher energy (quality) photons as well as amplitude (graph question)
    increase kVp
  64. the more photons you have the higher ______
    the energy and increase in amplitude
  65. describe a brems intereaction
    happens when an incident electrons loses energy from bending at the forcefield of the nucleus thus the xray photon is weaker
  66. describe characteristic interaction
    An incident electron interacts with an inner shell electron, knocking out the inner shell electron and continuing in a slightly different direction, which creates a hole in the inner shell, making the shell unstable.
  67. what is the avg keV of the primary beam coming down at 90 kVp
    • 27-36 keV is the avg compared to 90
    • this is 30-40 % of 90
  68. describe characteristic cascade
    The reaction of electrons dropping into the holes created during a characteristic interaction until there is only a hole in the outer shell
  69. what percentage of the primary beam is contributed to the off focus radiation (ch.6)
  70. what is the purpose of cooling curves and tube rating charts? (ch.6)
    used as safety measure to avoid thermal damage to the tube
  71. what are the three types of charts and cooling curves
    • tube rating charts
    • anode rotating disk
    • housing cooling curves
  72. what is ma(time)
  73. which charts are most valuable out of the three charts
    tube rating charts because they are a guide regarding the maximum technical factor combinations that can be used without overloading the tube
  74. what are the three technical factors plotted on these charts
    mA kVp time
  75. does each filament for each tube have its own tube rating chart
  76. what are cooling and housing charts are calculated, what measurement
    heat units (HU)
  77. what is the formula for figuring out heat units
    kVp x mA x time x rectification constant
  78. better xray machines use what kind of rectification constant
    high frequency constant
  79. list the followin rectification constants:
    • single phase full wave (worst) = 1.00
    • 3 phase 6 pulse (medium) = 1.35
    • 3 phase 12 pulse = 1.41
    • high frequency (best) = 1.45
  80. describe a brems interaction
    An incident electron reacts with the force field of the nucleus, causing the electron to slow down, diverting the electron’s course; the electron loses energy and changes direction; the energy lost in the "braking" is a bremsstrahlung photon.