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RADBIO
Stochastic Effects
| Term | Definition |
|---|---|
| (Deterministic/Stochastic) effects of radiation exposure are the result of low doses delivered over a long period. | stochastic |
| Radiation exposures experienced by personnel in diagnostic imaging are (low/high) dose and (low/high) linear energy transfer (LET); they are chronic in nature because they are delivered intermittently over long periods. | low : low |
| Radiation _______________ guides are based on suspected or observed stochastic effects of radiation and on an assumed linear, nonthreshold dose-response relationship. | protection |
| The principal stochastic effects are; | radiation-induced malignancy & genetic effects |
| Stochastic effects of radiation exposure exhibit an increasing incidence of ___________—not severity—with increasing dose. | response |
| Our radiation protection guides are based on the stochastic effects of radiation and on ________, ________________ dose-response relationships | linear, nonthreshold |
| Study of the occurrence, distribution, and causes of disease in humans. | epidemiology |
| A response that was developed on early radiologists who perform fluoroscopy; the skin appeared calloused, discolored, & weathered hands and forearms; skin characteristics - very tight, brittle and severely cracked or flaked. | radiodermatitis * The dose needed to produce this effect should be HIGH. |
| Irradiation of blood-forming organs can produce _______________ _____________ as a deterministic response or _____________ as a stochastic response. | hematologic depression : leukemia |
| In 1932 Ernest O. Lawrence of the University of California developed the first ______________, a 12-cm-diameter device capable of accelerating charged particles to very high energies. | cyclotron * E.O. Lawrence received the 1939 Nobel Prize in Physics. |
| Chromosome damage in the circulating ________________ can be produced as both a deterministic and a stochastic response. | lymphocytes |
| The modern cyclotron is used principally to produce ________________ for use in nuclear medicine, especially fluorine-18 for positron emission tomography. | radionuclides |
| E.O. Lawrence’s brother, _______ _____________, MD, was the first physician to apply radionuclides (from his brother’s cyclotron) on humans. | John Lawrence * He is the Father of Nuclear Medicine |
| In ________ the first paper reporting cataracts in cyclotron physicists appeared. By _______, several hundred such cases of radiation-induced cataracts had been reported. | 1949 : 1960 |
| Radiation-induced cataracts occur on the posterior pole of the _____. | lens |
| The radiosensitivity of the lens of the eye is ____ dependent. As the age of the individual increases, the radiation effect becomes (greater/smaller) and the latent period becomes (longer/shorter). | age : greater : shorter |
| Radiation-induced cataracts latent periods ranging from ________ years have been observed in humans, and the average latent period is approximately ____ years. | 5 -30 : 15 |
| High-LET radiation, such as neutron and proton radiation, has a (high/low) relative biologic effectiveness (RBE) for the production of cataracts. | high |
| The dose-response relationship for radiation-induced cataracts is _____________, _____________. | nonlinear, threshold |
| If the lens dose is high enough, in excess of approximately _________, cataracts develop in nearly 100% of those who are irradiated. | 10 Gyt (1000 rad) |
| [ RADIATION-INDUCED CATARACTS ] Acute x-ray exposure threshold: __________________ Fractionated exposure threshold: ________________ Occupational eye dose: Too low for protective shields to be needed | ~2 Gy (200 rad) : >10 Gy (1000 rad) |
| In computed tomography the lens dose can be __________. In either case, protective lens shields are not normally required. | 50 mGyt (5 rad) |
| At worst, humans can expect a reduced life span of approximately ____ days for every _________. | 10 : 10 mGyt |
| Whereas the average life shortening caused by occupational accidents amounts to _____ days, for radiation workers, life is shortened by only ____ days. | 74 : 12 |
| Radiologists dying in the early 1930s were approximately ___ years younger than members of the general population who died at an average age. This difference in age at death had shrunk to zero by 1965 | 5 |
| A stochastic effect that occurs simply as accelerated premature aging and death. | radiation-induced lifespan shortening |
| Precise dose-response relationships are often not possible to formulate, and we therefore resort to risk estimates. There are three types of risk estimates— | relative, excess, and absolute risk |
| Estimation of late radiation effects in large populations without precise knowledge of their radiation dose. | relative risk |
| Formula of Relative Risk | Observed cases -------------------- Expected cases |
| This is computed by comparing the number of persons in the exposed population showing a given stochastic effect with the number in an unexposed population who show the same stochastic effect. | Relative Risk |
| RR of ____ : no risk at all RR of ____ : frequency of a late response is 50% higher in the irradiated population than in the nonirradiated population RR of ____: suggests a protective benefit from radiation (radiation hormesis theory). | 1.0 : 1.5 : < 1 |
| The relative risk for radiation-induced stochastic effects of particular importance observed in human populations is in the range of _______. | 1 - 2 |
| Proposes low radiation doses (<100 mGy / 10 rad) may stimulate molecular repair and immune responses. | radiation hormesis * Radiation hormesis is still a theory, and ALARA (as low as reasonably achievable) remains the standard practice. |
| An estimation of the difference between observed and expected numbers of cases and it determines the magnitude of late effect. | excess risk |
| Formula of Excess Risk | ER = Observed cases - Expected cases |
| Incidence of malignant disease in a population within 1 year for a given dose; expressed as number of cases/10^6 persons/rem. | Absolute risk |
| The absolute risk of a fatal radiation-induced malignant disease is __________________. | 5 × 10^−2 Sv^−1 (5 × 10^−4 rem^−1) |
| A risk metric that is useful for comparing disease incidence rates in irradiated vs. non-irradiated populations. | relative risk |
| To determine the number of ___________ ______, one must be able to measure the observed number of cases in the irradiated population and compare this with the number that would have been expected on the basis of known population levels. | excess risk |
| Radiation-Induced Incidence Risk: ________________ Radiation-Induced Mortality Risk: ________________ | 8 × 10^−2 Sv^−1 (8/10,000/10 mSv) : 5 × 10^−2 Sv^−1 (5/10,000/10 mSv) |
| A number of human population groups have exhibited an elevated incidence of leukemia after radiation exposure— | - atomic bomb survivors - American radiologists - radiotherapy patients - children irradiated in utero |
| Radiation-induced Malignancy Examples: | thyroid/liver/bone/lung/skin/breast cancer |
| Radiation-induced leukemia is considered to have a latent period of _________ years and an at-risk period of approximately ____ years. | 4 - 7 : 20 |
| The ________ ________ is that time after irradiation during which one might expect the radiation effect to occur. | at-risk period * The at-risk period for radiation-induced cancer is lifetime. |
| (TRUE/FALSE) Studies of radiation-induced leukemia among American radiologic technologists consistently show no evidence of any radiation effect. | TRUE |
| When this incidence of leukemia is compared with that of the general population, the relative risk is ________. | 10 : 1 |
| Approximately ____% of all deaths are caused by cancer; therefore, any radiation-induced cancers are obscured. | 20 |
| When ingested, the _________ behaves metabolically similar to calcium and deposits in bone. | radium |
| Radiation-induced skin cancer follows a ______________ dose-response relationship. | threshold |
| When the dose delivered to the skin was in the range of ______________ , the relative risk of developing skin cancer was 4 : 1. | 5 -20 Gyt (500 -2000 rad) |
| In some of these patient populations the relative risk for radiation-induced breast cancer was shown to be as high as _________. | 10 : 1 |
| Radiation-induced breast cancer exhibits a _________, _______________ dose-response relationship. | linear, nonthreshold |
| Studies suggest radiation-induced breast cancer in patients treated with __________ Gy of x-rays for postpartum mastitis, with a relative risk of ~_____. | 0.75–10 : 3:1 |
| Now it is known that radiation exposure from _______ in the mines contributed to the incidence of lung cancer in these miners. The radiation exposure in these mines occurred because of the high concentration of __________ ore. | radon : uranium |
| ________ is an alpha-emitting radionuclide that adsorbs on dust particles, which lodge in the alveolar spaces of the lung. One of the decay products of uranium. | Radon |
| To date, more than 4000 uranium miners have been observed, and they have received estimated doses to lung tissue as high as _________; on this basis, the relative risk was approximately ______. | 30 Gyt (3000 rad) : 8 : 1 |
| Thorium dioxide (ThO2), used as a contrast agent in angiography between 1925 and 1945, was in a colloidal suspension called _____________, containing radioactive thorium isotopes and emitting alpha, beta, and gamma radiation in a 100:10:1 ratio. | Thorotrast |
| The overall absolute risk for induction of malignancy is approximately _____________ with the at-risk period extending for 20 to 25 years after exposure. | 8 cases/100 Sv |
| The risk of death from radiation-induced malignant disease is ________________. | 5 cases/100 Sv |
| Before pregnancy, the concern is ______________ __________. During pregnancy, concern is directed to possible ______________ effects in newborns. Post-pregnancy concerns are related to suspected __________ effects. | interrupted fertility : congenital : genetic |
| The ____________ risk model predicts that the excess radiation-induced cancer risk is constant for life. | absolute |
| The __________ risk model predicts that the excess radiation-induced cancer risk is proportional to the natural incidence. | relative |
| Exposure at an (early/late) age can result in an excess bulge of cancer after a latent period. | early |
| (TRUE/FALSE) Low-dose, chronic irradiation does impair fertility. | FALSE |
| All observations point to the first trimester (during/after) pregnancy as the most radiosensitive period | during |
| The effects of radiation in utero are time related and radiation dose related. They include; | 1. prenatal death 2. neonatal death 3. congenital abnormalities 4. malignancy induction 5. general impairment of growth 6. genetic effects 7. mental retardation |
| Within 2 weeks of fertilization, the most pronounced effect of a high radiation dose is ___________ death, which manifests as a spontaneous abortion. | prenatal |
| The first ___ weeks of pregnancy may be of least concern because the response is all-or-nothing. | 2 |
| A dose of 100 mGyt (10 rad) during _______________ is expected to increase the incidence of congenital abnormalities by 1% above the natural incidence. | organogenesis |
| The relative risk of childhood leukemia after irradiation in utero is _____. | 1.5 |
| Radiation exposure in utero does retard the growth and development of the ___________. | newborn |
| A concern in irradiation of utero that causes the least concern because it is an all-or-none effect. | spontaneous abortion |
| Based on Muller's studies, radiation (increases/decreases) the frequency of spontaneous mutations without altering their quality, showing no dose rate or fractionation effects, and concluding that mutations are single-hit phenomena. | increases |
| The ____________ ______ is that dose of radiation that produces twice the frequency of genetic mutations as would have been observed without the radiation. | doubling dose |
| ____________ risk is calculated when the population’s radiation dose is not known. __________ risk determines the magnitude of the stochastic effect as the difference between cases and control subjects. | Relative : Excess |
| In 1927, Nobel Prize-winning geneticist ______________ irradiated mature Drosophila (fruit flies) before procreation and measured the frequency of lethal mutations in their offspring. | H.J. Muller |
Created by:
yulyae