Ch. 3 Safety Flashcards
Radiation that possesses the ability to remove electrons from atoms by a process called ionization
Ionizing radiation
Effects of radiation on the body being irradiated
Somatic effects
Effects of radiation on the genetic code of a cell; affects the next generation
Genetic effects
Radiation contained in the unpolluted environment
Natural background radiation
Also called man-made radiation (medical x-rays)
Artificially produced radiation
Radiation exiting the x-ray tube
Primary radiation
X-rays that emerge from the patient and strike the image receptor
Exit radiation (remnant radiation or image-producing radiation)
Absorption and scatter (loss of intensity) of the x-ray beam as it passes through the patient
Attenuation
X-ray beam that contains photons of many different energies
Heterogeneous beam
Absorption of x-ray photons in the atoms of the body
Photoelectric effect
Organization that publishes radiation protection guidelines for the United States
National Council on Radiation Protection and Measurements (NCRP)
Scatter of x-ray photons from the atoms of the body
Compton effect
Unit of exposure
Air kerma
Unit of absorbed dose, measured in joules per kilogram (J/kg), 1 Gy = 1 J/kg
Gray
Unit of radiation absorbed in air
Gray a
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
Effective dose limit
Unit of radiation absorbed in tissue
Gray t
Unit of effective dose and equivalent dose
Sievert
Lifetime occupational exposure must not exceed the radiographer’s age multiplied by 10 mSv
Cumulative effective dose
Equal to the effective dose multiplied by the radiation weighting factor
Equivalent dose
Concept of radiologic practice that encourages radiation users to adopt measures that keep the dose to the patient and themselves at minimal levels
As low as reasonably achievable (ALARA)
Graphs that illustrate the relationship between radiation dose and the response of the organism to exposure; may be linear or nonlinear, threshold or nonthreshold
Dose-response curves
Randomly occurring effects of radiation; the probability of such effects is proportional to the dose (increased dose equals increased probability, not severity, of effects)
Stochastic (probabilistic) effects
Effects of radiation that become more severe at high levels of radiation exposure and do not occur below a certain threshold dose
Tissue reactions (deterministic)
Amount of energy deposited by radiation per unit length of tissue
Linear energy transfer (LET)
Effect that occurs when radiation directly strikes DNA in the cellular nucleus
Direct effect
Effect that occurs when radiation strikes the water molecules in the cytoplasm of the cell
Indirect effect
Effect that 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 (HOH+) and a free electron
Radiolysis of water
Erroneous information passed to subsequent generations via cell division
Mutation
Cells are most sensitive to radiation when they are immature, undifferentiated, and rapidly dividing
Law of Bergonié and Tribondeau
Hematopoietic syndrome; gastrointestinal (GI) syndrome; central nervous system syndrome
Early somatic effects of radiation
Carcinogenesis; cataractogenesis; embryologic effects; thyroid dysfunction; life span shortening
Late somatic effects of radiation
Distance, time, shielding
Cardinal principles of radiation protection
Best protection against radiation exposure
Distance
Optically stimulated luminescence (OSL) badge, thermoluminescent dosimeter (TLD), digital ionization dosimeter
Personnel monitoring devices
Average dose of radiation to the bone marrow
Mean marrow dose
Results of ionization in human cells
Unstable atoms, free electrons, production of low-energy x-rays, formation of new molecules harmful to the cell, cell damage may be exhibited as abnormal function or loss of function
Pair production
Does not occur in radiography, is produced at photon energies greater than 1.02 million electron volts. and involves an interaction between the incoming photon and the atomic nucleus.
What is the source of exposure to the radiographer or radiologist during fluoroscopy?
Compton scatter
What does photoelectric interaction results in?
Complete absorption of an incoming x-ray photon; this interaction produces contrast in the radiographic image
Compton interaction results in what?
Scattering of the incoming x-ray photon; scatter produced by this interaction must be removed from the beam before it strikes the image receptor.
What are the three main parts of a cell?
Cell membrane, cytoplasm, and nucleus.
What is the function of the cell membrane?
To protect the cell, holds in water and the nucleus, and allows water, nutrients, and waste products to pass into and out of the cell.
What are the four subphases of mitosis?
Prophase, Metaphase, Anaphase, and Telophase.
What does DNA control?
Cell division and all cellular functions.
Prophase is when
The nucleus enlarges.
Metaphase is when
The nucleus elongates.
What is Anaphase?
Two complete sets of chromosomes.
What is the purpose of Telophase?
To separate the two sets of genetic material; division complete; 46 chromosomes in each new somatic cell.
As LET of radiation increases
So does biological damage.
Free radicals are?
Highly reactive ions that have an unpaired electron in the outer shell
What results of an indirect effect?
No effect, formation of free radicals, and formation of H2O2.
Epithelial tissue is
Highly radiosensitive, divides rapidly, lines body tissue.
Muscle is
relatively insensitive because of high specialization and lack of cell division.
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 very radiosensitive, divide rapidly, unspecialized, require 10 rads or more to increase chances of mutation?
Immature sperm cells.
What in the female fetus and child are very radiosensitive?
Ova
When does ovarian radiosensitivity decrease?
It decreases until near middle age, then increases again.
Direct effect occurs when?
radiation transfers its energy directly to the DNA or RNA
Cell line death is
The death of the tissues or organs that would have been produced from continued cell division had a cell survived.
Oxygen Enhancement Ratio [OER]
If cells are more oxygenated, they are more susceptible to radiation damage.
What are the most radiosensitive blood cells in the body?
Lymphocytes
Early tissue reactions include
Erythema, epilation, decreased blood count, and acute radiation syndrome.
Hematopoietic syndrome
Decrease in total number of all blood cells
GI syndrome
Death from serious damage to the lining of the intestines
Central nervous system (cerebrovascular) syndrome
Causes complete failure of nervous system and results in death from increased fluid in the brain.
Late tissue reactions include
Cataractogenesis, thyroid cancer or cessation, effect on fertility
Stochastic effects include
Carcinogenesis, nonmalignant radiodermatitis, embryologic effects (most sensitive during first trimester), and genetic mutations.
Doubling dose is
The amount of radiation that causes the number of mutations in a population to double (is approximately 1.56Sv for humans)
Interphase
Portion of the cellular life cycle that occurs before mitosis
Mitosis is
Somatic cell division; includes four phases: prophase, metaphase, anaphase, and telophase
What happens mitosis is complete?
Each new cell contains 46 chromosomes
Meiosis is
Germ (sperm or ovum) cell division; halves the number of chromosomes in each cell so that the union of two germ cells produces a new cell with 46 chromosomes
Beam limiters consist of
Collimator, cylinder cones, aperture diaphragms
Lead aprons
Must be at least 0.25-mm lead equivalent; should be at least 0.5-mm lead equivalent
What source of radiation is the radiographer exposed to?
Scatter radiation produced by Compton interactions in the patient during fluoroscopy, portable radiography, and surgical radiography.
Primary protective barriers
Must be at least 1/16 inch lead equivalent and extend from the floor to a height of 7 feet
Secondary protective barriers
Must be at least 1/32 inch lead equivalent and extend from the primary protective barrier to the ceiling with a ½-inch overlap
