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51 Cards in this Set
- Front
- Back
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As Low As Reasonably Achievable (ALARA)
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-synonymous w/ optimization for
radiation protection (ORP) -keep radiation exposure and consequent dose to the lowest possible level -should be main part of every health care facility's personnel radiation control program, and should be established and maintained for pts -radiation-induced cancer doesn't have a threshold/dose level below which individuals would have no chance of sustaining this disease |
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Background Equivalent Radiation Time (BERT)
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-compares amount of radiation
received from a radiographic procedure w/ natural background radiation received over a given period of time (i.e. days, weeks, months, or years -does NOT imply radiation risk; is simply a means for comparison -emphasized that radiation is an innate part of our environment -answer given in BERT is easy for the pt to comprehend |
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Biologic Damage/Effects
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-damage to living tissue of animals
and humans exposed to radiation |
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Genetic Damage
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-biologic effects of ionizing radiation or
other agents on generations yet unborn |
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Cellular Damage
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-injury on the cellular level caused by
sufficient exposure to ionizing radiation at the molecular level -can lead to abnormal or loss of cell function |
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Diagnostic Efficacy
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-degree to which the diagnostic study
accurately reveals the presence or absence of disease in the pt -provides basis for determining whether an imaging procedure or practice is justified |
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Effective Dose (EfD)
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dose that takes into account the dose for all types of ionizing radiation to human organs or tissues and the overall harm (i.e., the weighting factor) of those biologic components for the development of a radiation-induced cancer (or, for the reproductive organs, the risk of genetic damage)
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Electromagnetic Spectrum
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the complete range of frequencies and energies of electromagnetic radiation
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Electromagnetic Wave
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electric and magnetic fields that fluctuate rapidly as they travel through space, including radio waves, microwaves, visible light, and x-rays
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Equivalent Dose (EqD)
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-quantity that attempts to take into
account the variation in biologic harm that is produced by different types of radiation -SI unit: sievert (Sv) |
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Radon
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-the 1st decay product of radium
-accounts for approx. 55% of the gross common exposure of human beings to natural background radiation -colorless, odorless, heavy radioactive gas that along w/ its decay products, polonium-218 and polonium-214 (solid form), is always present to some degree in the air |
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Ionizing Radiation
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-produces positively and negatively charged particles (ions) when
passing through matter -only x- and gamma radiation |
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Manmade/Artificial Radiation
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-ionizing radiation created by humans
for various uses -consumer products containing radioactive material, air travel, and medical radiation -nuclear fuel for generation of power -nuclear power plant accidents -atmospheric fallout from nuclear weapons |
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Natural Background Radiation
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-ionizing radiation from environmental
sources -has 3 components: terrestrial, cosmic, and internal (from radionuclides) |
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Occupational and Nonoccupational Dose Limits
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the upper boundary doses of ionizing radiation that result in a negligible risk of bodily injury or genetic damage
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Organic Damage
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genetic or somatic changes in a living organism (i.e., mutation, cataracts, and leukemia) caused by excessive cellular damage from exposure to ionizing radiation
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Radiation
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energy in transit from one location to another
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Radiation Dose
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amount of energy transferred to electrons by ionizing radiation
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Radiation Protection
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effective measures used by radiation workers to safeguard pts, personnel, and the general public from unnecessary exposure to ionizing radiation
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Radionuclide
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an unstable nucleus that emits one or more forms of ionizing radiation to achieve greater stability
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Terrestrial Radiation
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long-lived radioactive elements present in variable amounts in the earth's crust that emit densely ionizing radiations
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Cosmic Radiation
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-rays from the sun (solar) and beyond
the solar system (galactic) -the intensity of cosmic rays varies w/ altitude relative to the earth's surface -the greatest intensity occurs at high altitudes, and the lowest intensity occurs at sea level |
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Particulate Radiation
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-includes alpha and beta particles,
neutrons, and protons -these subatomic particles are ejected from atoms at very high speeds -they possess sufficient kinetic energy to be capable of causing ionization -vary in their ability to penetrate matter |
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Alpha Particles
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-are helium nuclei (i.e., helium ions)
-emitted from nuclei of very heavy elements such as uranium and plutonium during the process of radioactive decay -have a large mass (approx. four times the mass of a hydrogen atom) and a positive charge twice that of an electron -less penetrating than beta particles -lose energy quickly as they travel a short distance in biologic matter (i.e., into the superficial layers of the skin) -considered virtually harmless as an external source of radiation -a piece of ordinary paper can absorb them or function as a shield |
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Beta Particles
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-aka: beta rays
-identical to high-speed electrons except for their origin -like alpha particles, beta particles are emitted from the nuclei of radioactive atoms -approx. 8000x lighter than alpha -small mass and negative charge -capable of penetrating biologic matter to a greater depth than alpha and w/ far less ionization along their paths |
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Absorbed Dose (D)
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-deposition of energy per unit mass by ionizing radiation in the pt's body tissue
-this absorbed energy is responsible for whatever biologic damage occurs as a result of tissues being exposed to x-radiation -the gray (Gy) is the SI unit for this radiation quantity |
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Absorption
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transference of electromagnetic energy to the atoms of a material
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Attenuation
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the reduction in the number of primary photons in the x-ray beam through absorption (a total loss of radiation energy) and scatter as the beam passes through the object in its path
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Auger Electrons
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--when a vacancy exists in an inner electron shell of an atom (as the result of photoelectric effect, Compton scattering, or bombardment by other electrons) an outer-shell electron drops into the vacancy, and energy equal to the difference in binding energy between the two shells must be released by the atom
-this energy may be released as a characteristic photon, or it may be released as an electron, an outer-shell electron that is ejected from its shell -any energy beyond the energy required to release the Auger electron appears as kinetic energy of the Auger electron |
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Characteristic Photon
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-a quantum or quantity of radiant energy given off by the parent atom when an electron from an outer shell drops down to fill an inner-shell vacancy after the atom has interacted w/ an x-ray photon and lost an inner-shell electron as a result
-the energy of a characteristic photon is equivalent to the difference in energy level between the two electron shells |
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Coherent Scattering
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-the process wherein a low-energy photon interacts w/ an atom as a whole, and the atom responds by releasing the excess energy it has received in the form of a scattered photon that has the same wavelength and energy as the original incident photon but emerges from the atom moving in a slightly different direction
-aka: Rayleigh, classical, elastic, and unmodified scattering |
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Compton Scattered Electron
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an energetic electron dislodged from the outer shell of an atom of the irradiated object as a result of interacting w/ an incoming x-ray photon
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Compton Scattering
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-an interaction between an incoming x-ray photon and a loosely bound outer-shell electron of an atom in the irradiated object
-the photon surrenders a portion of its kinetic energy to dislodge the electron from its outer-shell orbit and then continues in a new direction -this process accounts for most of the scattered radiation produced during diagnostic procedures |
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Negative Contrast Media
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the use of air or gas to enhance visualization of body structures during a radiologic procedure
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Positive Contrast Media
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a liquid solution containing an element w/ a higher atomic number than surrounding tissue (e.g., barium or iodine) that is either ingested or injected into biologic tissues or structures to be visualized
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Effective Atomic Number (Zeff)
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a composite atomic number for a material that consists of different chemical elements
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Exit, or Image-Formation, Photons
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all of the x-ray photons that reach their destination (the image receptor) after passing through the object being radiographed; previously known as remnant radiation
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Fluorescent Yield
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the number of characteristic x-rays emitted by an atom per created inner-shell vacancy
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Mass Density
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-quantity of matter per unit volume
-generally specified in units of kilograms per cubic meter or grams per cubic centimeter |
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Milliampere-seconds (mAs)
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the product of electron tube current and the amount of time in seconds that the x-ray tube is on
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Pair Production
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-interaction between an incoming photon of at least 1.022MeV and an atom of the irradiated object in which the photon approaches, strongly interacts w/ the nucleus of the atom of the irradiated material, and disappears
-in the process, the energy of the incoming photon is transformed into two new particles-a negatron and a positron-after which these particles exit from the atom, carrying away some of the momentum of the absorbed photon when the photon's energy is greater than 1.022MeV |
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Peak Kilovoltage (kVp)
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highest energy level of photons in the x-ray beam
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Photodisintegration
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-an interaction that occurs above 10MeV in high-energy radiation therapy machines in which a high-energy photon collides w/ the nucleus of an atom, absorbing all of the photon's energy
-this energy excess in the nucleus creates an instability that can be alleviated by the emission of a neutron by the nucleus -if sufficient energy is absorbed by the nucleus, another type of emission is possible: a proton or proton-neutron combination (deuteron) |
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Photoelectric Absorption
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-an interaction between an x-ray photon and an inner-shell electron in which the photon surrenders all its kinetic energy to the orbital electron and ceases to exist
-as a result, the electron escapes its inner shell and leaves the atom -is the process most responsible for the contrast between bone and soft tissue in diagnostic radiographs |
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Photoelectron
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the electron ejected from its inner-shell orbit during the process of photoelectric absorption
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Primary Radiation
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radiation that emerges directly from the x-ray tube collimator and moves w/o deflection toward a wall, door, viewing window, and so on; aka: direct radiation
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Radiographic Contrast
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differences in density level between the radiographic images of objects in a radiograph
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Radiographic Density
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the degree of overall blackening on the finished radiograph
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Radiographic Fog
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undesirable, additional density on a processed radiographic film caused by scattered radiation reaching the film
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Radiographic Image Receptor
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radiographic film or phosphorescent screen
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Small-angle Scatter
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photons that pass through the object being radiographed interact w/ the atoms of the object and are deflected at such a small angle that they can reach the film, thereby degrading the radiographic image by producing small amounts of radiographic fog
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