Card Set Information

2014-04-28 12:32:44

Show Answers:

  1. light field and field congruence, beam flatness and symmetry, and field size indicators  should be checked
  2. How much mass does an electron have
    virtually none
  3. orthovoltage machines operate in the range of
    150-500 KV
  4. .01 joule is = to
    • 1 rad
    • 1 gray = 1 joule = 100 rad= 100 cgy
  5. What is the traditional and Si unit of the absorbed dose equivalent
    • Rem is the traditional and
    • Sievert is the SI unit
  6. What is the traditional and Si unit of ionization in air/exposure
    • Roentgen is the traditional and
    • Coulomb is the SI unit
  7. Ion chambers depend on the ______ _____ in air and ____ and ____ are required for the readings
    • ionization effect
    • voltage and current
  8. annual dose limit for the general public is
    .1 rem or 1 msv
  9. The ____ _____ contains ferrous sulfate, sodium chloride, and sulfuric acid. The monitoring process relies on chemical reaction following exposure.
    Frickle dosimeter
  10. For a controlled area, the shielding must be sufficient to reduce exposure to no more than
    .1 rem/week or 100mrem/week
  11. For stochastic effects, the probability of a late effect is ______
    dose dependent

    probability is dose dependent
  12. The energy of an electromagnetic radiation is inversely proportional to its
  13. What is the traditional and SI unit for activity
    • Curie is the traditional and
    • Becquerel is the SI unit
  14. All photons in the spectrum have the same
    • velocity, mass, and charge
    • NONE

    They just have different energies
  15. wavelengths are measured in
  16. As the wavelength of light is decreased the speed is
    • unchanged
    • the speed remains the same even as the wavelength decreases
  17. The HDR brachytherapy room should have a zone monitor that
    indicates any potential exposure
  18. LET is measure in
  19. What is the basic unit of energy
  20. Symmetry and flatness are defined over ___ of the field
  21. Physical field size is defined at the ___ of the isodose line
    • 50%
    • but defined at 100cm
  22. Photoelectric effect decreases with increasing photon energy. Beyond ____, the fraction of radiation interactions in water and tissue attributed to the photoelectric effect are negligible.
    • 150 keV
    • this is why the photoelectric effect is least important in radiation therapy
  23. What produces extra nuclear indirectly ionizing radiation?
    • the linear accelerator
    • Photons are produced by a linac thru the bremsstrahlung interaction that occurs when electrons impinge on the target. Bremsstrahlung occurs outside of the nucleus
  24. what energy of a photon is detected by PET
    511 kV
  25. Linear attenuation coeffiecient is the fraction of photons attenuated per unit of
  26. What is the energy threshold for triplet production
    2.044 MV
  27. A wedge angle is defined as the isodose angle   relative to the central axis at
    a depth of 10 cm
  28. TMR is defined as ratio of dose at any depth to the dose at
  29. The photoelectric effect _____ with increasing photon energy.
    decreases because if the photon energy is high enough, then the incoming photon would interact with the outershell electron and then be known as compton interaction which is why the compton interaction is the most common in radiation therapy.
  30. mass attenuation is _____ of density

    It is dependent on the thickness
  31. True or False HVL is = to ln2/u  and 0.693/u (
  32. A high energy beam photon strikes an orbital electron and scatters it exactly 180 degrees, what is the max energy of the scatter photon
    255 kV
  33. Increasing the mAs will
    increase the current which will increase the # of photons in the xray beam. It relates to the density. KvP is related to the contrast and energy
  34. Cobalt 60 decays giving off
    2 gamma rays of 1.17 and 1.33 MeV
  35. Which effects are more sensitive to increased overall tx time
    acute effects
  36. Which effects depend on total dose and dose per fraction?
    late effects
  37. Which effect has no dose threshold?
  38. When protons interact with matter, the rate of ionization increases as the proton is slowed down in matter and the energy can be given off as
  39. Penumbra increases with source size and SSD but is _____ of field size
  40. In SSD tx's the dose is normalized at _____ and in SAD tx's dose is normalized at _____
    • dmax
    • tx depth
  41. If the threshold of 1.022 MeV is not present for B+ decay to occur, then a nucleus with an excess # of protons will release energy by
    electron capture
  42. What is the most common used source in HDR afterloading brachytherapy and whyu
    IR-192 because it has a high specific activity and lower photon energy
  43. The average 1/2 life of a source with a 1/2 life of 32 min would be
    • 46 minute
    • 1.44 (32)
  44. The skin dose in the case of electrons beams is
    • 80-90%
    • electrons do have a little skin sparing just not much
  45. PET is based on imaging with photons produced in annihilation of _____ by _____
    positrons by electrons
  46. Dose to the lumpectomy site following APBI HDR will approx be
    40-50 GY
  47. To find the inverse square factor, divide the distances and
    square them. do not multiply by the dose because you are only looking for the factor
  48. backscatter depends on what two things
    field size and energy of the beam NOT distance
  49. In the maintenance phase of ALL, whole brain irradiation may be administered using
    the helmet technique which includes C2
  50. Hypogastric lymph nodes are part of the _______and would likely be included in fields for ______
    • external iliac chain of nodes
    • rectal carcinoma
  51. Why is Lucite a preferred holder material for the custom block compensator and blocks?
    to reduce the potential for electron contamination
  52. The shape of the isodose curves depends on what 4 things
    • field size
    • flattening filters
    • accessories like blocks, wedges, and cones
    • MLCs
  53. When treating the oropharynx, the junction should be placed cephalad of the thyroid notch to avoid overdosing the
  54. When treating thyroid cancer you would include what 3 things
    • the lesion
    • both scv
    • superior mediastinum
  55. When using rotational arc, MU or treatment time should be calculated using the ____ method
  56. The acceptable amt of transmission thru a MLC is
  57. Carbon fiber is preferred material for the pt couch  because of its
    • radiolucency
    • and low attenuation
  58. Increasing the dose rate on the linac will ____ the PDD
    not change
  59.  Custom shielding blocks that are divergent reduce
    beam edge cutoff
  60. When adjacent fields are used to treat deep tumors, the fields should be
    separated on the skin and overlap at depth. The skin gap should be calculated so that the beams overlap at depth beyond any critical organs
  61. Most txs are delivered on a linac with a SAD of
  62. When is the xray output constancy and electron output constancy checked and what is the tolerance
    Daily 3%
  63. Isotopes have the same
    Isobars have the same
    Isotone have the same
    Isomer have the same
    • Protons and everything else different
    • Atomic mass P & N but everything else diff
    • Neutrons and everything else different
    • Same everything
  64. 100 rem = how many SV
    • 1 SV
    • measures dose equivalent
  65. Main Cervix Staging
    • T1- Confined to cervix
    • T2- Into Vagina and parametrium
    • T3- Into Pelvic wall
    • T4-Into bladder, Rectum etc
  66. Main Hodgkin Staging
    • T1- 1 lymphnode involvement
    • T2- 2 or more lymphnodes but on the same side of the diaphragm
    • T3- Lymphnodes on both sides of the diaphragm
    • T4- multifocal into the liver and bone marrow
  67. Main Larynx Staging
    • T1- Limited to cord with mobility
    • T2- Extends to supra and sub glottis and cord impairment
    • T3- Limited to Larynx but cord immobile
    • T4- Extends beyond larynx
  68. Main Breast staging
    • T1- 2 cm or less
    • T2- between 2 and 5 cm
    • T3- greater than 5 cm
    • T4- any size with extension into skin and chestwall
  69. Embryo fetus exposure
    total and monthly
    • Total      5msv
    • Monthly .5 msv
  70. Public frequent and infrequent
    • Frequent     1msv
    • Infrequent  5msv
  71. Occupational
    Annual stochastic
    non stochastic lens
    skin, extremeties etc
    • Annual stochastic     50 msv
    • non stochastic lens   150 msv
    • skin, extremeties etc 500 msv
  72. WBC count level
    • 4,000-10,000
    • less than 2000 critical
  73. RBC count
    4-6 million
  74. Platelet count
    • 150,000-500,000
    • less than 50,000 is critical
  75. blood pressure
    • Systolic- 95-140
    • diastolic-  60-90
  76. hemoglobin range
    • 13-17
    • less than 10 is critical
  77. hematocrit level range
    • 38-49%
    • less than 34 is critical
  78. Normal BUN range
  79. permanent hair loss starts at what dose
    • 50 GY
    • temporary is 15-30 GY
  80. Esophagitis dose is
    20-25 GY
  81. Thoracic Vertebrae size
    Lumbar Vertebrae size
    • Thoracic 2.5 X 8
    • Lumbar 3-3.5 X 8
  82. Mass attenuation is ___ of density
  83. Whole brain stem TD 5/5
    2/3 brain stem
    1/3 brain stem
    • 5000
    • 5300
    • 6000
  84. Optic chiasm TD 5/5
  85. Optic nerve TD 5/5
  86. When protons interact with matter, the rate of ionization increases as the proton slows down in matter AND energy can be given off as
  87. Which photon interaction with matter involves energy being converted to mass
    pair production
  88. Which image modality yields the poorest quality when visualizing soft tissue
    mega voltage portal image because they are highly penetrating
  89. Will increasing the field size increase the PDD
    • Yes
    • PDD increases with increase in
    • field size
    • beam energy
    • distance and
    • depth past dmax
  90. The magnification factor divides what by what
    image size/actual object size
  91. Which type of thyroid cancer is characterized by rapid growth and local invasion of structures

    papillary and follicular grow very slowly but Papillary is the most common thyroid cancer
  92. What is the ratio of absorbed dose at a given depth in phantom to the absorbed dose at the same point at a given reference depth of 10 cm?
  93. What type of dose response model applies to MRI address biologic effects of the magnetic fields used to image patients?
    non linear, threshold
  94. The average photon beam energy produced by a 6 MV linear accelerator is approv ____ MV
    • 2
    • To get the average photon energy divide by 3.....