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Radiography
Radiation Protection
| Question | Answer |
|---|---|
| What is the formula for the inverse square law? | I1/I2=D2(squared)/D1(spuared). |
| Late or Long term effects of radiation exposure are | Linear Nonthreshold ("all or nothing"). |
| Nonstochastic effects | are those that will not occur below a particular threshold dose and that increase in severity as the dose increases. |
| According to the NCRP, the annual occupational whole-body dose equivalent limit is | 50 mSv (5 rem or 5000 mrem). |
| The annual occupational whole-body dose equivalent limit for students under the age of 18 years is | 1 mSv (100 mrem or 0.1 rem). |
| The annual occupational dose equivalent limit for the lens of the eye | is 150 mSv (15 rem or 15,000 mrem). |
| The annual occupational dose equivalent limit for the skin and extremities | is 500 mSv (50 rem or 50,000 mrem). |
| The total gestational dose equivalent limit for embryo/fetus of a pregnant radiographer | is 5 mSv (0.5 rem or 500 mrem). |
| Photoelectric Effect | a relatively low-energy incident photon uses all of its energy to eject an inner-shell electron, leaving a vacancy. An electron from the next shell will drop to fill the vacancy, and a characteristic ray is given up in the transition. |
| Compton scatter | highenergy incident photon ejects outershell elec. incident photon is dflctd w/reduced ener but usual keeps most of its energy & exits body as energetic sctrd ray. Sctrd ray will ethr help 2 image fog or pose a rad hazard 2 techs, dpndng on drctn of exit |
| Classical Scatter | a low-energy photon interacts with an atom but causes no ionization; the incident photon disappears into the atom, and is then immediately released as a photon of identical energy but changed direction. |
| Thompson Scatter | is another name for classical scatter |
| The x-ray interaction with matter that is responsible for the majority of scattered radiation reaching the IR is | Compton Scatter |
| The following formula is used to determine Effective Dose (E): | Effective Dose (E) = Radiation Weighting Factor (Wr) × Tissue Weighting Factor (Wt) × Absorbed Dose |
| The Radiation Weighting Factor (Wr) | is a number assigned to different types of ionizing radiations in order to better determine their effect on tissue (eg, x-ray vs alpha particles). |
| The Tissue Weighting Factor (Wt) | represents the relative tissue radiosensitivity of irradiated material (eg, muscle vs intestinal epithelium vs bone, etc). |
| Inverse Square Law | exposure rate is inversely proportional to the square of the distance; that is, if the SID is doubled, resulting beam intensity will be one 4th the orig intensity; if SID is cut in half, resulting beam intensity will be four times the original intensity. |
| Somatic effects are | those induced in the irradiated body. |
| Genetic Effects are | effects that may not appear for many of years. |
| Isobars are | atoms with the same mass number but different atomic numbers. |
| Isotones | have the same number of neutrons but different atomic numbers. |
| Isomers | have the same atomic number and mass number; they are identical atoms existing at different energy states. |
| Rem (dose-equivalent) is the only unit of measurement that expresses | the dose-effect relationship. |
| In radiation protection, the product of absorbed dose and the correct modifying factor (rad × QF) is used to determine | rem (Sv). |
| Explain Linear Dose-response curve | has no threshold; that is, there is no dose below which radiation is absolutely safe. |
| Explain The nonlinear/sigmoidal dose-response curve | has a threshold and is thought to be generally correct for most somatic effects—such as skin erythema, hematologic depression, and radiation lethality (death). |
| Rad measures | the energy deposited in any material |
| Roentgen is | the unit of exposure; it measures the quantity of ionizations in air. |
| Rem is | an acronym for radiation equivalent man; it includes the RBE specific to the tissue irradiated and therefore is a valid unit of measurement for the dose to biologic tissue. |
| The unit of measurement used to express occupational exposure is the | Rem (Sv) |
| The Curie is | the unit of radioactivity, describing disintegrations per second. |
| Describe X-rays used for Diagnostic purposes: | is of relatively low energy. Kilovoltages of up to 150 are used, as compared with radiations having energies of up to several million volts. X- and gamma radiations, having no mass or charge, are low-LET radiations. |
| Isotpes are | atoms of the same element, with the same Atomic# (# of protons), but different Mass# (# of Neutrons). |
| Radiation-induced malignancy, leukemia, and genetic effects are | late effects (or stochastic effects) of radiation exposure. These can occur years after survival of an acute radiation dose, or after exposure to low levels of radiation over a long period of time. |
| If 600 rad or more is received as a whole-body dose in a short period of time, certain effects will occur; these are referred to as | Acute Radiation Syndrome. |
| Scattering | occurs when there is partial transfer of the proton's energy to matter, as in the Compton effect. |
| Absorption occurs | when an x-ray photon interacts with matter and disappears, as in the photoelectric effect. |
| The reduction in the intensity (quantity) of an x-ray beam, as it passes through matter, is termed | Attenuation |
| Divergence refers | to a directional characteristic of the x-ray beam, as it is emitted from the focal spot |
| Somatic effects of radiation refer to | those effects experienced directly by the exposed individual, such as erythema, epilation, and cataracts. |
| Genetic effects of radiation exposure are caused by | irradiation of the reproductive cells of the exposed individual and are transmitted from one generation to the next. |
| What are some secondary barriers | Secondary barriers protect from secondary (scattered and leakage) radiation. Secondary barriers are control booths, lead aprons, and gloves, and the wall of the x-ray room above 7 feet. |
| Nonstochastic effects are | those that will not occur below a particular threshold dose and that increase in severity as the dose increases. |
| Describe Stochactic Effects | Most late effects do not have a threshold dose; that is, any dose, however small, theoretically can induce an effect. Increasing that dose will increase the likelihood of the occurrence, but will not affect its severity. |
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Thevictory
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