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2014-04-04 01:00:09

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  1. what is linear energy transfer
    when passing through something ionizing radiation may interact with it during its passage and as a result deposits energy along its track
  2. what is an important factor in assessing potential tissue and organ damage from exposure to ionizing radiation
  3. what is considered low LET
    low let causes damage through what kind of interactions
    • electromagnetic radiation like xrays and gamma rays
    • indirect interactions
  4. what are repair enzymes
    they reverse cellular damage to dna from radiation
  5. high LET radiation do not _______ far but cause ______ ionizations in a shorter length of track
    when is high let of great concern
    • penetrate
    • many

    when it is ingested inhaled or radionuclide implanted
  6. high let does what damage to DNA
    irrepairable damage caused by multiple strand breaks
  7. What is RBE and what does it stand for
    when LET increase what also increases
    • relative biologic effectiveness
    • it is the capabilities of radiation with differing LET's to produce a particular biologic reaction
    • RBE
  8. what is OER and what does it stand for
    • oxygen enhancement ration
    • oxygen enhancement ratio is numerical value of the ratio of radiation dose required to cause a particular biologic response of cells or
    • organisms in an oxygen deprived environment to the radiation dose required to cause an identical response under normal oxygenated conditions
  9. why does oxygen in biologic tissue makes the damage produced by an indirect action permanent
    because O2 combines with free radical to produce organic peroxide compounds
  10. damage to what cells can result in genetic mutations
    germ cells
  11. most interactions that are involved with ionizing radiation are ______?
    another term for an indirect interactions with radiation is ______
    • indirect interactions
    • radiolysis
  12. what happens during a direct action
    the damage results from ionization of atoms on master molecules leading to inactive or dysfunctional molecules
  13. what is an indirect action
    is caused by the interaction of free radicals with water molecules (radiolysis) which in turn disrupt the master molecule and lead to cell death
  14. two free radicals (OH) can combine to form what and are poisonous (toxic) to the cell
    H202 hydrogen peroxide
  15. what is a single strand break and when is it commonly associated with
    • energy transferred from ionizing radiation to a DNA molecule can break one of the chemical bonds on one side of the sugar phosphate side rail
    • associated with low let radiation (gamma and xray)
  16. double strand breaks occur during what type radiation
    what is a double strand break
    • high let radiation
    • multiple strand breaks in the sugar phosphate side rails
  17. what is double strand break in the same rung of the DNA
    a broken chromosome
  18. what is mutation
    • is the loss or change in a nitrogenous base in the DNA chain
    • which causes incorrect information being sent over to the daughter cells
  19. what are covalent links
    are chemical unions create between atoms by the single sharing of one or more pair of electrons
  20. what are the possible effects of ionizing radiation on chromosomes
    restitution - breaks rejoin with no visible damage deletion - part of chromosome is lost at the next division broken end arrangement - misshape chromosome produced broken end rearrangement - genetic material is rearranged damage not visible results in mutation
  21. what is the target theory
    the belief that there is a master or key molecule in the cell(DNA) and that it is necessary for the ssurvival of the cell
  22. when can the target theory be deactivated
    when exposed to ionizing radiation
  23. what are the cellular effects of irradiation(7)
    • instant death
    • reproductive death
    • apoptosis (interphase death) - occurs normally
    • mitotic or genetic death
    • mitotic delay
    • interference of function
    • chromosome breakage
  24. what is instant death
    how much Gy is associated with it
    does this occur in diagnostic and therapeutic range
    • happens when a large volume is irradiated with a dose of 1000GY(100000 RADS) in a period of a few seconds or minutes a large number of cells will die instantly
    • no
  25. what is reproductive death
    when does it occur (how much Gy)
    • occurs after doses of 1-10grays (100-1000rad)
    • cell doesnt die it loses its ability to replicate and the damage is not transmitted to new generations of cells
  26. which areas of the body handle radiation better smaller or larger (whole body)?
    smaller areas of the body
  27. what is apoptosis (programmed cell death)
    what is it known as
    when does it occur
    • Nonmitotic the cell dies during interphase without attempting to divide
    • interphase death
    • spontaneously in normal tissue and tumors in humans
  28. what happens to the cell in apoptosis and what does it produce
    what do blebs do
    • cell shrinks and produces tiny membrane enclosed structures called blebs
    • blebs break up cell and nucleus and ingest each other
  29. what amount radiation is need for apoptosis to occur in bone and lymphocytes and spermatogonia (meausred in Gy)
    • bone = several thousand gy
    • lymphocytes and sperm = few hundred gy
  30. what is mitotic (genetic) death
    occurs when the cell dies after one or more divisions following inhibition of reproduction by radiation
  31. what is mitotic delay
    when can this occur (level of dose)
    • happens when the cell doesnt divide on time but can resume normal mitotic function
    • small as 1 rad
  32. what is interference of function
    it is temporary or permanent dependent on the ability of the repair enzymes to fix the damage
  33. the presence of what element promotes indirect damage through the formation of free radicals
  34. what can be used to promote tumor radiosensitivity in order to destroy it
    • a highly pressured (hyperbaric) oxygen setting or oxygen
    • by increasing o2 in the capillaries of the tumor they become more sensitive and responsive to radiation
  35. where are hypoxic cells commonly found
    why are the cells more difficult to destroy through indirect interaction
    • in tumors
    • because it has very low oxygen
  36. what is a chemical agent that can increase the radiosensitivity of a tumor
  37. what is the law of bergione and triboneau
    radiosensitivity is directly proportional to reproductive activity and indirectly proportional degree of differentiation
  38. what cells and phases are most radiosensitive
    immature cells are AKA?
    • immature cells w/high reproductive activity and long mitotic phases
    • unspecialized/undifferentiated cells
  39. unspecialized cells are cells that are _____
    unspecialized are known as _____
    • immature or constantly reproducing
    • cells of embryo -fetus
    • undifferentiation/immature
  40. Specialized/differentiated cells are ____
    cells that do not reproduce as rapidly
  41. list radioresistant and radiosensitive cells
    • radioresist. = bone muscle and nerve cells, sperm and egg (less sensitive than immature verison)
    • radiosensitive = blood cells immature wbcs, spermagonia, oogonia (germ cells), intestinal crypt cells basal skin cells
  42. what is the worst break in the dna chain
    base break
  43. what dose (Gy) of radiation will cause a measurable decrease in circulating blood cells
    this does what to the stem cells
    • 25 rad (.25gy
    • causes a decrease in immature stem cells produced depletion increases as bone marrow dose increases
  44. what is LD-50/30
    what is the LD expressed in humans and how much radiation is required in GY
    stands for lethal dose required to produce death in 50% of the population in 30 days

    • LD-50/60
    • 300-400 RAD(3-4gy)
  45. what is the most radiosenstive cell in the body and what are they collectively known as
    what are the three groups of lymphocytes
    • Leukocytes or lymphocytes (wbc's)
    • lymphocytes
    • neutrohpils
    • granulocytes
  46. what are the precursors to RBC's and what is their degree of sensitivity to radiation
    mature blood cells are ______
    • erythrocytes
    • they are very sensitive
    • less sensitive
  47. what are the other RBC's and their precursors
    • megakaryoblasts = platelets (precursor)
    • myeloblasts = granulocytes
  48. what is the typical wbc count in the body
  49. what is the function of lymphocytes and
    defend body against antigens as depletion increases ability to fight infection decreases
  50. which cells has the shortest life span in 24 hrs of blood cells 
    which wbc manufactured where are most radiosensitive
    • lymphocytes
    • when manufactured in bone marrow
  51. why are patients platelt count monitored frequently in therapeutic dose imaging
    because they recieve more radiation and these high doses cause decrease in blood count
  52. when do chromosomal aberrations occur in lymphocytes
    • high level fluoro
    • very long flouro exposure times
  53. list all epithelial tissue that are highly _____ and are ________ to radiation found where
    • mitotic
    • highly sensitive
    • instestinal lining
    • respiratory tract
    • pulmonary alveoli
    • blood and lymph vessel lining
  54. reproductive cells of the male and female are highly ______
  55. what is the window of maximum sensitivity for pregnant women
    8-15wks after gestation
  56. what dose of radiation results in a 4% chance of mental retardation
    10 rem
  57. routing abdominal fluoro case will result  in a fetal equivalent dose of ____
  58. mature spermatogonia are _______ to radiation
    insensitive or  more resistant
  59. a dose of _____ is enough to cause temporary sterility for 12 months
    a dose of ______ is enough to cause permanent sterility
    doses as low as _____ can do what to sperm count
    • 200-300rad = 2-3 gy
    • 500-600 rad = 5-6gy
    • 10rad; depress
  60. what is fractioned and protraction doses
    • fractioned doses are radiation received over a period of time or wks
    • protraction doses radiation given at a single time over long amt of hours
  61. what the principle radiation effects on the embryo/fetus (list 3)
    • loss of pregnancy
    • mental retardation
    • malformations

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