Unit 5 (Late Effects)

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Unit 5 (Late Effects)
2013-03-12 01:26:41
Radiation Biology

Unit 5: Late effects of radiation on organ systems
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  1. —an increase of exposure results in __________ chance of interaction.
    an increase
  2. an increase of exposure __________ severity.
    does not increase
  3. —our radiation protection guides are based on the late effects of radiation and on:
    linear, nonthreshold dose-response relationship
  4. in late effects, diagnostic exposure is:
    low LET and chronic
  5. late effects are the result of:
    while the early effects result from:
    • late: low doses delivered over long periods of time
    • early: high doses of radiation
  6. Personnel  in diagnostic imaging experience _________________________ over a long time span.
    low doses and low LET periodically
  7. two primary long term effects resulting from low dose radiation over long periods of time:
    • malignancy
    • genetic effects
  8. there is not a specific dose to relate to various late effects such as:
    • malignancy
    • genetic effects
    • life-span shortening
    • local tissue effects
  9. what is the method of choice when studying late effects?
    epidemiological method
  10. when a large number of people exposed to toxic substance requiring considerable statistical analyses:
    epidemiological method
  11. name some problems that arise with the epidemiological method:
    • the dose is usually not known but presumed to be low
    • the frequency of response is very low
    • —**this results in less statistical accuracy than early effects**
  12. inflammation of the skin caused by exposure to x-rays or emissions from radioactive particles:
  13. give examples of radiodermatitis:
    • —callused, discolored  and weathered appearance
    • skin very tight and brittle
    • late-developing carcinoma
    • —(erythema early effect takes 200 rads)
  14. in chromosomal effects of radiation to local tissue, _______________ is the early effect while _____________ is the late effect.
    • hematologic depression (25 rads)
    • leukemia
  15. —chromosomal damage in the _________________ can take place in both early and late effects
    • circulating lymphocytes
    • (early: 5 rads chromosomal aberration)
  16. may not become apparent until many years after the radiation exposure:
    low dose aberration
  17. radiation exposure can remain in the peripheral lymphocytes for as long as:
    • 20 years
    • (if lymphocyte stem cells are irradiated, they may not undergo replication and maturation for many years - this explains the possible delay)
  18. who developed the first cyclotron, when, and what was its principle use?
    • E. O. Lawrence
    • 1932
    • to produce radionuclides for use in nuclear medicine, and fluorine-18 in PET
  19. where are the largest cyclotrons in the world located?
    Argonne National Laboratory in the U.S. and CERN in Switzerland
  20. describe how the cyclotron contributed to cataracts:
    • physicists used a fluorescent screen to locate the high energy beam which resulted in very high doses to the lens of the eye
    • by 1960, several hundred cases of cataracts were reported in the high-energy physics
  21. where do high energy cataracts form?
    in the posterior pole of the lens
  22. concerning cataracts, —radiosensitivity of the lens is ____________, the latent period varies from ___________ years, and the average latent period is _____ years.
    • age dependent
    • 5-30 years
    • 15 years.
  23. High LET such as ______________ radiation have a ______ RBE for the production of cataracts.
    • neutron and proton 
    • high
  24. dose-response relationship for cataracts is:
    nonlinear, threshold
  25. concerning cataracts, —acute threshold is _________; chronic threshold is approximately _________.
    • 200 rads (acute)
    • 1000 rads (chronic)
  26. in CT, a patient can receive up to _______ per slice intersecting the lens of the eye.  On average, the lens may be intersected ______ resulting in _______ to the lens of the eye.
    • 5 rads
    • twice
    • 10 rads
  27. concerning the late effects of radiation in life-span shortening,  dose response is:
    linear, nonthreshold
  28. concerning the late effects of radiation in life-span shortening - at worst, humans can expect a reduced life span of:
    approximately 10 days per rad
  29. give some examples of life-span shortening:
    • radiation worker: 12 days
    • —being male rather than female: 2800 days
    • heart disease: 2100 days
    • being married: 2000 days
    • one pack of cigarettes a day: 1600 days
    • working as a coal miner: 1100 days
    • cancer: 980 days
    • 30 pounds overweight: 900 days
    • airplane crashes: 1 days
    • motor vehicle accident: 200 days
  30. the period after the prodromal stage of the acute radiation syndrome during which there is no visible sign of radiation sickness:
    latent period
  31. time period a person could actually die from a disease brought on by radiation:
    risk period
  32. what are the three types of risk estimates in late effects of radiation?
    • relative risk
    • excess risk
    • absolute risk
  33. when one observes a large population for late radiation effects without having any precise knowledge of the radiation dose to which they were exposed:
    relative risk
  34. determined by the number of observed cases in the irradiated population and comparing
    them with the number that would have been expected on the basis of known population levels:
    excess risk
  35. when one must assume a linear dose-response relationship and if the dose-response relationship is assumed to be nonthreshold, then only one dose level is required:
    absolute risk
  36. which type of risk estimate deals with observed or expected cases?
    relative risk
  37. name some human population groups affected by leukemia as a radiation-induced malignancy:
    • —atomic bomb survivors
    • american radiologist
    • radiation therapy patients
    • children irradiated in utero
  38. radiation-induced leukemia follows what type of dose-response relationship?
    linear, nonthreshold
  39. describe leukemia cases in atomic bomb survivors:
    from 100,000 atomic bomb survivors, cases hit a plateau at 5 years and declined slowly for approximately 20 years
  40. describe the latent and at-risk periods for leukemia as a radiation-induced malignancy:
    • latent period of 4 to 7 years
    • at-risk period of approximately 20 years
  41. give some causes of leukemia occurring as a radiation-induced malignancy:
    • radiologist receiving over 100rads/yr
    • ankylosing spondylitis patients receiving radiation for relief
    • radiation therapy patients relapsing with leukemia
  42. when studying the effects of cancer as a radiation malignancy, ______ of all deaths are due to cancer which can obscure the data.
  43. list three examples of thyroid cancer occurring as a radiation-induced malignancy:
    • —500 rads for thymic enlargement in newborns resulted in thyroid nodules and cancer 20 years later
    • native children of rongelap atoll in 1954 were exposed to an excess of 1200 rads from the fallout of a hydrogen bomb test
    • chernobyl 1986, recent studies have shown no excess leukemia or cancer, but there was an increase in thyroid nodularity
  44. give an example of bone cancer occurring as a radiation-induced malignancy:
    • —1920-1930 watch dial painters exposure to high amounts of radium (half-life 1620 years); ingested radium metabolizes like calcium which resulted in as much as 50,000 rads to the bone
    • today tritium and promethium is used for the glow purpose without the excessive exposure
  45. concerning skin cancer as a radiation-induced malignancy, give the following:
    how it begins
    induced by
    latent period
    risk factors
    • how it begins: radiodermatitis
    • induced by: radiation therapy  orthovoltage (200-300kVp) or superficial xray (50-150kVp)
    • latent period: approximately 5-10 years
    • risk: 500-2000 rads relative risk of 4:1, 4000-6000 rads risk of 14:1, 6000-10000 rads risk of 27:1
  46. describe aspects of breast cancer occurring as a radiation-induced malignancy:
    • —patients were treated for TB with fluoroscopy of the chest to induce a pneumothorax in affected lung
    • patients would receive as much as several hundred rads per treatment
    • the relative risk of radiation induced breast cancer due to this procedure was found to be 10:1
    • patients also treated with 75 to 1,000 rads for postpartum mastitis resulting in a relative risk factor of 3:1
    • atomic bomb survivors of 10 rad or more showed a relative risk of 4:1
  47. describe some aspects/locations of lung cancer occurring as a radiation-induced malignancy:
    • —50% of bohemian mines of germany died of lung cancer
    • today it is known that radon found in the mines contributed to the lung cancer of these miners
    • radiation exposure in colorado mines are contributed to high levels of uranium (half-life 10,000,000,000 years) 
    • a decay product of uranium is radon, a radionuclide capable of emanating through rock to produce a high level in the air to be breathed
  48. describe some aspects of liver cancer occurring as a radiation-induced malignancy:
    • —thorium dioxide made up 25% of thorotrast media used during 1925-1945 for angiography
    • latent period of 15 to 20 years
    • thorium dioxide deposited in phagocytic cells of the reticuloendothelial system and concentrated in the liver and spleen
  49. concerning late effects, give the risk period for:
    bone cancer
    and the latent period for:
    skin cancer
    • bone cancer: 50 yrs
    • leukemia: 20 yrs
    • skin cancer: 5-10 yrs
    • leukemia: 4-7 yrs
    • liver: 15-20 yrs
    • thyroid: 5-10 yrs
    • cataracts: 5-30 yrs
  50. give information concerning total risk of malignancy when it comes to three mile island:
    • —2,000,000 people residing in 80 km radius near the susquehanna river in pennsylvania
    • ave. doses were 160 km-1.5 rad, 80km-8mrad
    • —20% of population will have cancer considering statistics not taking into account the additional exposure from three mile island
    • prediction is 1.2 deaths due to exposure
  51. be familiar with this chart:
    BEIRS: Biologic Effects of Ionizing Radiation
  52. a relationship in which the increased incidence of cancer is a constant number of cases after a minimal latent period:
    absolute age-response relationship
  53. a relationship where the increased incidence of cancer is proportional to the natural incidence:
    relative age-response relationship
  54. what are the three main concerns dealing with radiation and pregnancy (before, during, after)?
    • before: concern with interrupted fertility
    • during: possible congenital effects in newborns
    • after: related to genetic effects
  55. ____________ irradiation does NOT impair fertility.
  56. describe what we know about the risks of radiation during pregnancy (in utero):
    • —all observations point to first trimester during pregnancy as the most radiosensitive period
    • the first 2 weeks of pregnancy may be of least concern because the response is all-or-nothing
    • relative risks: 1st trimester-8.3, 2nd trimester-1.5, 3rd trimester-1.4, total-1.5
    • relative risk of childhood leukemia after irradiation in utero is 1.5
  57. radiation effects occurring to offspring as a result of radiation exposure in-utero:
    teratogenicity effects
  58. name some examples of teratogenicity:
    • —death-embryonic, fetal, neo-natal
    • microcephaly
    • hydrocephaly
    • spina bifida
    • club feet
    • mental retardation
    • skeletal abnormalities
    • abnormalities of internal organs
    • diminished growth and development
    • childhood malignancy
  59. that dose of radiation that produces twice the frequency of genetic mutations as would have been observed without the radiation:
    doubling dose
  60. —radiation induced mutations are usually:
  61. genetic effects of radiation during pregnancy depend on:
    protraction and fractionation
  62. are most genetic mutations dominant or recessive?
  63. —radiation-induced genetic mutations is extremely low, at:
    .000001 mutation/rad/gene
  64. name some genetic effects that can occur from radiation during pregnancy:
    • —increased risks of malignancy
    • increased spontaneous abortions and stillbirths
    • increased infant mortality
    • increased congenital effects
  65. name two general facts about genetic effects:
    • there is no data suggesting radiation induced genetic effects in humans
    • —follow a single-hit model(more damage being done to an immature/undifferentiated type cell)
  66. a theory that states small amounts of radiation can be good for humans:
    radiation hormesis
  67. according to the theory of radiation hormesis,  —__________________ can possibly stimulate molecular repair and immunologic response mechanisms.
    approximately 10 rads