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Radiography

Radiation Protection

QuestionAnswer
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.
Created by: Thevictory