Rad Bio 10/19 Test

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  1. The four R's of radiation therapy?
    • Repopulation
    • Reoxygenation
    • Redistribution
    • Repair of sublethal damage
  2. IMRT
    Intensity Modulated Radiation Therapy
  3. TD
    The tissue tolerance dose associated with a 5% injury rate within 5 years
  4. TD
    The tissue tolerance dose associated with a 50% injury rate within 5 years
  5. Bladder TD 5/5
    • Bladder TD 5/5:
    • 6000 cGy
    • (contracture)
  6. Rectum TD 5/5
    • Rectum TD 5/5:
    • 6000 cGy
    • (ulcer, stricture)
  7. Lens of the Eye TD 5/5
    • Lens of the Eye TD 5/5:
    • 500 cGy
    • (blindness)
  8. Fetus TD 5/5
    • Fetus TD 5/5:
    • 200 cGy
    • (death)
  9. Heart TD 5/5
    • Heart TD 5/5:
    • 4500 cGy
    • (pericarditis, pancarditis)
  10. Intestine TD 5/5
    • Intestine TD 5/5:
    • 4500 cGy
    • (ulcer, perforation, hemorrhage)
  11. Kidney TD 5/5
    • Kidney TD 5/5
    • 1500 cGy
    • (acute & chronic nephrosclerosis)
  12. Liver TD 5/5
    • Liver TD 5/5
    • 2500 cGy
    • (acute & chronic hepatitis)
  13. Lung TD 5/5
    • Lung TD 5/5
    • 3000 cGy
    • (acute & chronic pneumonitis)
  14. Spinal Cord TD 5/5
    • Spinal cord TD 5/5
    • 4500 cGy
    • (infarction, necrosis)
  15. LD 50/60 for humans
    350-450 cGy

    The lethal dose for 50% of the population in 60 days
  16. Who is typically most sensitive to hematopoetic syndrome?
    Men, the very old & very young, infirm
  17. Pancytopenia
    The depression of all blood cell counts
  18. What is the most radiosensitive portion of the digestive system?
    • The small intestine
    • 4500cGy
  19. In hematopoetic syndrome is probability of survival dose dependent?
    • yes
    • probability of survival decreases as dose increases
  20. LD 100 for humans
    1000 cGy

    100% of humans exposed to 100cGy will die
  21. Fetal development
    0-10 days
    • Preimplantation
    • 0-10 days 
  22. Fetal development
    Day 10-6 weeks
    • Embryo
    • Day 10-6 weeks
  23. Fetal development
    Week 7 - birth
    • Fetus
    • week 7 - birth
  24. Bid
    Twice a day
  25. Tid
    Three times a day
  26. Hematopoetic Syndrome
    Time of death
    • hematopoetic symdrome
    • 100-1000cGy
    • death in 3 weeks - 2 months
  27. Gastrointestinal Syndrome
    Time of death
    • gastrointestinal syndrome
    • 1000-10,000 cGy
    • death in 3-10 days
  28. Cerebrovascular Syndrome
    Time of death
    • cerebrovascular syndrome
    • anything over 10,000cGy but can occur as low as 5,00cGy
    • death in less than 3 days
  29. Doubling dose
    The dose required to double the mutation frequency in a generation due to radiation exposure
  30. What is the maximum permissible dose to the fetus?
    0.5rem (5mSv)
  31. What is the latent period for leukemia due to radiation?
    4-7 years
  32. Latent period
    The time interval between irradiation and the appearance of malignancy.
  33. NSD
    Nominal Standard Dose
  34. NTTD
    Normal Tissue Tolerance Dose 
  35. What are the 2 factors that affect NTTD?
    • 1. The volume irradiated
    • 2. The fraction size
  36. How long does it usually take for people to recover from doses less than 300cGy?
    3-6 months
  37. 300-500cGy total body exposure
    When will death occur?
    • 300-500cGy
    • 4-6 weeks
  38. 500-1000 cGy total body exposure
    When will death occur?
    • 500-1000cGy
    • 2 weeks
  39. How do the effects of radiation in utero manifest?
    • -Lethal effect
    • -Congenital abnormalities present at birth
    • -Late effects observed years later
  40. What are the principle factors of fetal effects of radiation?
    • - Dose
    • - Stage of gestation at which it is delivered
  41. Late effects
    The biological response to low doses, not observable for extended periods.
  42. Somatic effects
    Late effects that involve body cells
  43. Genetic effects
    Late effects that involve reproductive (germ) cells
  44. The most important late somatic effect induced by radiation is:
  45. Thyroid cancer can appear from doses as low as 
  46. Mutation frequency
    the number of spontaneous mutations that occur in each generation of an organism
  47. Repair of Sublethal Damage 
    • -occurs within hours of exposure
    • -oxygen dependent, cells require a certain amt of oxygen to carry out repair mechanisms.
    • Because a proportion of tumor cells are hypoxic, tumors are presumed to be incapable of repairing sublethal damage 
  48. Reoxygenation
    Presumed to only apply to tumors

    The process by which hypoxic cells gain access to oxygen & become radiosensitive between XRT fractions
  49. Describe the four sub-populations of parenchymal tumors
    • Group 1: Growth Fraction (GF) viable, actively mitotic,    
    •      Responsible for tumor growth. 
    • Group 2: G0 cells; typically viable but nondividing.
    •      Can re-enter the cell cycle when stimulated
    • Group 3 & 4: Nonviable cells;
    •       Do not contribute to tumor growth
  50. The growth fraction (GF) typically                                as the size of the tumor increases.
    The growth fraction (GF) typically DECREASES as the size of a tumor increases.
  51. 3 major factors affecting tumor growth
    • 1. The division rate of proliferating parenchymal cells
    • 2. The percentage of these cells in the tumor (GF)
    • 3. The degree of cell loss from the tumor (f)
  52. A tumor with a radius of less than                  generally does not contain necrotic areas
    • less than 100um
    • (no necrosis)
  53. A tumor with a radius of greater than                       generally contains a necrotic area surrounded by a viable rim of cells approx 100-180um thick
    greater than 160um
  54. oxic
    oxic- well oxygenated
  55. hypoxic
    hypoxic- oxygen deficient; between oxic and anoxic
  56. Anoxic
    anoxic- lack or absence of oxygen
  57. Diffusion distance
    70um for oxygen in a tumor
  58. Hypoxic Cells
    • Although hypoxic cells do not have normal levels of oxygen available to them, they are viable and capable of dividing.
    • hypoxic fraction is approx ~ 15% of tumor volume
  59. Oxygen tension
    During their early growth stages, tumors begin to outgrow their vascular supply. This results in differing levels of oxygen availability, known as oxygen tension (PO2)
  60. Viable Hypoxic cells
    Resistant to low LET radiations by a factor of up to 2.5 to 3.0.

    Presumed to be responsible for tumor regrowth after xrt
  61. A fractionated dose is                            biologically efficient  than a single dose
    LESS efficient
  62. Hyperfractionation
    Bid (twice daily)

    Tid (three times daily)
  63. As the volume of the organ treated increases, the tolerance dose for the whole organ                         

    as the volume goes up; the tolerance goes down
  64. As the size of the daily fraction increases, the cell killing 
                       , and the cell's ability to repair sublethal damage
    As the size of the daily fraction increases, cell killing INCREASES and the cell's ability to repair sublethal damage DECREASES  (thus resulting in a decrease in the radiation tolerance of normal tissue) 
  65. Isoeffect Curves
    Isoeffect curves relate the treatment schedule in terms of total dose & time w/ the clinical outcome, including early effects, late effects & tumor cure.

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Rad Bio 10/19 Test
2012-10-17 04:47:50
Radiation therapy radiation biology rad science

Radiation Biology 10/19 test
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