Physics Ch 14 Interactions

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RadiationTherapy
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199702
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Physics Ch 14 Interactions
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2014-01-02 23:00:39
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Radiation therapy physics 14
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Radiation physics chapter 14 test 3/1, interactions
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  1. Name the interaction:
    Pair Production
  2. Name the interaction:
    Coherent (Thompson/Raleigh) Scattering
  3. Name the interaction:
    Compton Scattering
  4. Name the interaction:
    Pair Production
  5. Name the interaction:
    Photoelectric scattering
  6. This consists of two neutrons & two protons bound together:
    (equivalent to a helium atom that has been stripped of its two electrons)
    Alpha particle (α)
  7. What is the origin of gamma rays (γ)?
    the Nucleus
  8. What is the origin of x-rays?
    the Electron rings
  9. A _________ particle is the same as an electron, but with a different origin
    • a Beta minus decay particle
    • (β-)
  10. Coherent (Thompson) scattering primarily occurs at energies below ______.
    10 KeV
  11. The result of Coherent scattering is to change the ________ of the incident photon without changing its ________.
    • Direction
    • Energy
  12. X-rays scattered back in the direction of the incident x-ray are called __________ radiation.
    Backscatter radiation
  13. The probability of Compton scattering ________ as x-ray energy ________.
    the probability of Compton scattering DECREASES as x-ray energy INCREASES.
  14. The ________ is total x-ray absorption.
    Photoelectric Effect
  15. An x-ray with less than _____ (energy) cannot undergo Pair Production.
    1.022 MeV
  16. The process by which the positron unites with a free electron and the mass of both particles is converted to energy:
    Annihilation Radiation
  17. As the number of protons grows larger, the _______ (more/less) neutrons are required to maintain stability.
    MORE protons = MORE neutrons
  18. Cobalt 60 decays by ______ decay to an excited state of _______.
    Cobalt 60 decays by BETA MINUS DECAY (β-) to an excited state of NICKLE (60Ni)
  19. Large, unstable atoms that have a large amount of excess energy tend to undergo radioactive decay by the emission of ___________.
    Alpha particles (α)
  20. During β- decay, this particle carries away the energy that is left over when the β- does not carry away all of the atom's excess energy:
    Antineutrino (νa)
  21. When a particle identical to an electron is emitted as a result of nuclear decay:
    Beta minus decay (β- decay)
  22. In β+ decay  the remainder of energy is carried away by the:
    Neutrino (ν)
  23. A subatomic particle that has exactly the same characteristics as an electron, except that it has a positive electrical charge:
    a Positron
  24. When a positron is ejected from an atomic nucleus, a nuclear proton decays into a neutron and a positron:
    Beta plus decay (β+ decay)
  25. When an electron strays too close to the nucleus, it can be captured and combined with a proton, reversing the process for β- decay:
    Electron capture
  26. Both _______ and _______ result in the Z of the parent nucleus being decreased by 1 and the N/Z ratio of the atom increases
    Electron capture & Beta plus decay (β+)
  27. Because of the proximity of the _____ shell to the nucleus, it is most likely that the captured electron will be taken from this shell, although it is possible to capture an electron from those farther away.
    K shell
  28. This type of radiation is a result of when an electron is taken from its shell, leaving a "hole" in the shell, thus placing the atom in an unstable configuration; then an electron from a higher shell to fall/cascade to a lower shell and losing energy in the form of an x-ray to become stable
    Characteristic radiation
  29. This represents a daughter product of some other kind of decay that is itself in an excited state, but instead of instantly decaying by gamma ray (γ) emission, it remains in this excited state for a given period of time & then decays.
    • Isomeric transition or Gamma decay
    • (γ decay)
  30. An isomer (identical Z and A of another atom) is said to be in this state:
    Metastable state
  31. The amount of radioactivity present in a sample is never a constant quantity but rather is being reduced continuously by the decay of the radioactive atoms in the sample. This decay process follows a mathematical pattern know as
    Exponential behavior
  32. The time period in which the activity decays to one half the original value:
    Half-life (th)
  33. Thickness of absorbing material necessary to reduce the x-ray intensity to half its original value.
    Half-value layer
  34. Half-life equation:

  35. The average lifetime for the decay of radioactive  atoms:
    Mean life
  36. A beam is called "______ intensity" if it has just a few photons per square centimeter, even if the photons are very high energy.
    Low intensity
  37. A beam is called " ______ intensity" if it consists  of a large number of photons, even if they are very low-energy photons.
    High intensity
  38. Removal of photos & electrons from a beam by scatter or absorption as it travels through a medium, typically tissue or tissue equivalent materials.
    Attenuation
  39. Half-value layer values are defined by the _______ of the beam and the _________.
    • Energy of the beam
    • &
    • Attenuating material
  40. What is this used to determine:
    Half Value Layer

  41. Photon beams can be classified as "hard" or "soft" beams depending on their ______.
    Half Value Layer (HVL)
  42. The effect of passing the beam through a lead attenuator to increase the overall HVL of the beam even though the intensity of the beam has probably been decreased:
    Beam Hardening
  43. Filtration that is built in to the machine:
    Inherent filtration
  44. In this interaction, the incident photon will change direction without losing any energy.
    Coherent (Raleigh) Scattering
  45. The probability of of various photon interactions with the atomic electrons & nuclei of the target depends on  the _______ of the photon and the __________ of the target material.
    • ENERGY of the photon
    • ATOMIC NUMBER (Z) of the target material
  46. ___________ is the thickness of the attenuator that reduces the beam intensity to 10% of its initial value.
    Tenth Value Layer (TVL)
  47. Name the interaction in which the incident photon is absorbed but lacks sufficient energy to ionize so the atom re-emits a photon of identical energy but in a different direction:
    Coherent Scattering
  48. Name the interaction in which the incident photon interacts the inner electron shells of an atom and an Auger electron is ejected:
    Photoelectric Scattering
  49. Which interaction produces characteristic radiation:
    Photoelectric Scattering
  50. Which interaction occurs primarily at energies below 10 KeV:
    Coherent Scattering
  51. What is the photon interaction that is most commonly witnessed in the energy ranges used in radiation therapy (1-5 MeV)?
    Compton scattering
  52. Which interaction occurs primarily at energies less than 1 MeV:
    Photoelectric scattering
  53. Which interaction is most commonly witnessed in diagnostic x-ray:
    Photoelectric scattering
  54. Name the interaction in which the incident photon interacts with free (outer) electrons and ejects an electron:
    Compton scattering
  55. Which interaction produces back-scatter?
    Compton scattering
  56. Name the interaction in which the incident photon passes close to the nucleus, is absorbed & instantly the energy is re-emitted as an electron-positron pair (β- , β+):
    Pair production
  57. The pair production interaction is physically impossible when the energy of the incident photon is less than __________
    1.022 MeV
  58. What is the energy of each the electron-positron pair (the result of pair production)
    0.511 MeV each
  59. Name the interaction in which the incident photon passes close to the nucleus:
    Pair production
  60. Name the interaction in which the incident photon strikes the nucleus:
    Photodisintegration
  61. Name the interaction in which the incident photon strikes the nucleus, is absorbed and then the atom emits both neutrons and gamma rays (γ rays) in an attempt to maintain stability:
    Photodisintegration
  62. Which interaction occurs mainly in high Z materials and at higher energies?
    Photodisintegration
  63. Which interaction can result in triplet production?
    Pair production
  64. Bremsstrahlung (braking) radiation
  65. Characteristic radiation and Auger electrons are emitted/ejected from the ________ while gamma rays are emitted from the ________.
    • Electron shells
    • Nucleus
  66. In which photon interaction(s) does the incident photon lose all of its energy?
    • Photoelectric
    • Pair Production
    • Photodisintegration
  67. Which photon interactions ionize the atom?
    • Photoelectric
    • Compton
  68. Which interactions do NOT ionize the atom?
    • Coherent
    • Pair Production
    • Photodisintegration
  69. What is the most important method of x-ray production in therapy machines?
    Bremsstrahlung
  70. Electrons lose approx ______ per cm of travel in water.
    2 MeV per cm
  71. The Law of Bergonie and Tribondeau states that ionizing radiation is more effective against cells that are:
    (3)
    • 1. actively mitotic
    • 2. are undifferentiated
    • 3. have a long mitotic future
  72. Arrange the cell types in order of radiosensitivity most to least:
    FPM
    MCT
    DIM
    RPM
    VIM
    • Radiosensitivity most to least:
    • VIM
    • DIM
    • MCT
    • RPM 
    • FPM
  73. During which phase of cellular mitosis are cells most and least radiosensitive?
    MOST: G-2

    LEAST: S

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