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Radt 465 SAFETY

ARRT registry review covering radiation protection content area

QuestionAnswer
Genetic effects Refers to effects of radiation on a germ cell’s genetic code; affects next generation
Heterogeneous beam x-ray beam that contains photons of many different energies
NCRP #116 makes recommendations pertaining to risk-benefit analysis of radiation exposure; defines annual exposure limits
Effective dose limit the upper boundary dose that can be absorbed, either in a single exposure or annually, with a negligible risk of somatic or genetic damage to the individual; effective dose implies whole body radiation exposure
Cumulative effective dose (CED) limit lifetime occupational exposure must not exceed the radiographer’s age multiplied by 1 rem
Equivalent dose Equal to the absorbed dose multiplied by the radiation weighting factor; formerly known as dose equivalent
Equivalent dose limit Upper boundary dose that can be absorbed, either in a single exposure or annually, with a negligible risk of a deterministic effect
Dose-response curves Graphs that illustrate the relationship between radiation dose and the response of the organism to exposure; may be linear or nonlinear, threshold or nonthreshold
Stochastic effects Randomly occurring effects of radiation; the probability of such effects is proportional to the dose (increased dose equals increased probability, not severity, of effects)
Deterministic effects Effects of radiation that become more severe at high levels of radiation exposure and do not occur below a certain threshold dose
Genetically significant dose (GSD) Average annual gonadal dose of radiation to individuals of childbearing age; addresses the relationship of gonadal doses to individuals versus an entire population and the overall effects
Linear energy transfer (LET) Amount of energy deposited by radiation per unit length of tissue
Relative biologic effectiveness (RBE) Ability to produce biologic damage; varies with the LET
Direct effect Occurs when radiation directly strikes DNA in the cellular nucleus
Indirect effect Occurs when radiation strikes the water molecules in the cytoplasm of the cell
Radiolysis of water Occurs as radiation energy is deposited in the water of the cell; the result of radiolysis is an ion pair in the cell: a positively charged water molecule and a free electron
Mutation Erroneous information passed to subsequent generations via cell division
Law of Bergonie and Tribondeau Cells are most sensitive to radiation when they are immature, undifferentiated, and rapidly dividing
Early somatic effects of radiation Hematopoietic syndrome, gastrointestinal syndrome, central nervous system syndrome
Late somatic effects of radiation Carcinogenesis, cataracogenesis, embryologic effects, thyroid dysfunction, life span shortening
Alpha particles and neutrons Are high-ionization radiations and have high LET (cause more biologic damage)
X-ray and gamma rays properties Are lower ionization radiations and have lower LET (cause less biologic damage)
Which dose-response curve indicates that no level of radiation can be considered completely safe and the response is directly proportional to the dose received? Linear-nonthreshold relationship
Which dose-response curve indicates that at lower doses of radiation exposure, no response is expected and the response is directly proportional to the dose received when exceeding the threshold? Linear-threshold relationship
An example of linear-threshold effect? Cataractogenesis
Which dose-response curve indicates that at lower doses of radiation exposure, no response is expected and the response is not directly proportional to the dose received? Nonlinear-threshold relationship
Which dose-response curve indicates that no level of radiation can be considered completely safe and the degree of the response is not directly proportional to the dose received? Nonlinear-nonthreshold relationship
What is the total equivalent dose for gestation of embryo-fetus? 0.5rem
Annual effective dose limit for occupational exposure 5rem
Cumulative effective dose (CED) limit equals age (in years) x 1 rem
Mitosis Cell division of somatic cells
Meiosis Cell division of sperm or ovum (germ cells) that halves the number of chromosomes in each cell
Target theory Each cell has a master molecule that directs cell activities
What are the most radiosensitive cells in the body? Lymphocytes
What are the least radiosensitive cells in the body? Adult nerve tissue: requires very high doses (beyond medical levels) to cause damage, is very specialized, has no cell division, is relatively insensitive to radiation
What is hematopoietic syndrome? An early somatic effects of radiation; decreases total number of all blood cells; can result in death
What is the thickness of the total filtration? Must equal 2.5mm aluminum equivalent for x-ray tubes operating above 70Vp
What is half-value layer? Amount of filtration that reduces the intensity of the x-ray beam to half of its original value_ measured at least annually by a qualified radiation physicist
What is the minimum source-to-skin distance for portable radiography? At least 12 inches
T/F: Family members of the patient, nonradiology employees, or radiology personnel not routinely exposed should be the first choices to assist with immobilization of the patient for an exam when all other types of immobilization have proved inadequate? True
NCRP report #102 Determines thickness recommendations for lead devices
Primary protective barriers Consist of 1/16-inch lead equivalent. If in the wall, extend from the floor to a height of 7 feet
Secondary protective barriers Consist of 1/32-inch lead equivalent. Extend from where primary protective barrier ends to the ceiling with a ½-inch overlap
The thickness of lead window by control booth? 1.5mm lead equivalent
What is the use factor? Amount of time the beam is on and directed at a particular barrier
The thickness of the protective curtain in fluoroscopy? Minimum 0.25mm lead equivalent
The thickness of Bucky slot shield? Minimum 0.25mm lead equivalent
when doing a portable x-ray, which area has the least scatter? At a 90 degree from the patient
what is the limit of x-ray tube leakage? May not exceed 100 mR per hour at a distance of 1 meter from the housing
which of the personnel monitor dosimeter that uses aluminum oxide to record dose? Optically stimulated luminescence (OSL) dosimeters
what does Thermoluminescent dosimeters (TLDs) use to record dose? Lithium fluoride crystals
What is the radiographer’s source of radiation exposure? Scatter radiation produced by Compton interactions in the patient during fluoroscopy, portable radiography, and surgical radiography
Example of primary barriers? The lead walls and doors of a radiographic room
Example of secondary barriers? The control booth, lead glasses, and apron
Created by: trangng