Terms ch. 3,4,5,8
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| Quality Assurance | Special procedures used to ensure the production of high-quality, diagnostic radiographs
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| quality administration | The management of the quality assurance plan in the dental office
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| Normalizing device | A commercially available device used to monitor developer strength and film density
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| quality control tests | Specific tests designed to maintain and monitor dental x-ray equipment, supplies, and film processing
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| radiograph, reference | A radiograph processed under ideal conditions and then used to compare the film densities of radiographs that are processed daily.
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| stepwedge | A device constructed of uniform-layered thicknesses of an x-ray absorbing material, usually aluminum; different steps absorb varying amounts of x-rays and are used to demonstrate film densities and contrast scales
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| viewbox | A light source used to view dental radiographs
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| Amperage | Determines the amount of electrons passing through the cathode filament. Increasing amperage: Results in an increased number of electrons traveling from cathode to anode and production of an increased number of x-rays
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| Contrast | how sharply dark & light areas are differentiated on an image. Low kVp settings (65-70 kVp)create high contrast film: Many black & white areas, few shades of gray. High kVp settings (≥ 90kVp) create low contrast image:Many shades of gray.
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| Density | Density: overall darkness or blackness of a image. When the kVp is increased, the image will be darker. When the kVp is decreased, the image will be lighter.
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| Exposure time | Exposure time affects the number of x-rays produced. A longer exposure time produces more x-rays and a more intense x-ray beam.
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| Half-value layer (HVL) | Alum. filters placed in path of beam inside tubehead.Filters remove low-energy, less penetrating, longer wavelength x-rays. Inc. mean penetrating capability of x-ray beam while reducing intensity. HVL: thickness of specified material cuts intenisty in 1/2
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| Intensity | The product of the quantity (number of x-ray photons) and quality (energy of each photon) per unit of area per unit of time of exposure
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| Inverse square law | Intensity of radiation inversely proportional to the square of distance from source of radiation. When the distance is doubled, the beam is 1/4 as intense. When the distance is halved, the beam is 4 times more intense.
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| Kilovoltage peak (kVp) | Regulates penetrating power of x-ray beam by controlling speed of electrons traveling b/w cathode and anode. Higher kVp settings: Produce x-ray beam w/ more energy & shorter wavelengths. Increases intensity of x-ray beam
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| Milliamperage | Controls the penetrating power of the x-ray beam by controlling # of electrons produced in the x-ray tube and the number of x-rays produced. Higher milliamperage settings: Produce an x-ray beam with more energy, increasing the intensity of the x-ray beam
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| Milliamperage & Exposure time | Milliamperage and exposure time are inversely related. When milliamperage is increased, exposure time must be decreased. When milliamperage is decreased, exposure time must be increased.
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| Milliampere-seconds (mAs) | mAs is the product of milliamperes and exposure time. When milliamperage is increased, exposure time must be decreased to maintain constant density.
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| Quality (of x-ray beam) | Wavelength determines the energy and penetrating power of radiation. X-rays with shorter wavelength have more penetrating power. Quality is used to describe the mean energy or penetrating ability of the x-ray beam. Quality is controlled by kilovoltage
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| Quantity (of x-ray beam) | number of x-rays produced in the dental x-ray unit; how many
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| Voltage | potential diff. b/w 2 electrical charges. Voltage inc.=electron speed inc. The electrons strike the target with greater force & energy. Voltage is measured in volts or kilovolts. Dental radiography requires the use of 65 to 100 kV.
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| Critical organ | Skin Thyroid gland Lens of eye Bone marrow
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| cumulative effects | Effects of radiation exposure are additive Unrepaired damage accumulates in tissues
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| Direct theory | cell damage results when ionizing radiation directly hits critical areas within the cell
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| dose, total | more damage occurs with larger quantities of radiation
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| dose equivalent | Compares biologic effects of different kinds of radiation; Traditional unit is the rem SI equivalent is the sievert 1 Sv = 100 rems
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| dose rate | more radiation damage takes place with a higher dose rate
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| dose-response curve | Linear, non-threshold relationship; Relationship indicates that response of the tissues is directly proportional to the dose;Non-threshold dose-response curve suggests: no matter how small the amount of radiation received, some biologic damage occurs.
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| free radical | Cell damage occurs primarily thru formation of free radicals. Free radicals formed when x-ray photon ionizes water.Free radical: An uncharged atom/molecule that exists with a single, unpaired electron in its outermost shell; Highly reactive & unstable
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| genetic cells | reproductive cells
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| genetic effects | Not seen in the person irradiated; Passed on to future generations
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| gray (gy) | sievert
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| Indirect theory | X-ray photons are absorbed within the cell and cause the formation of toxins, which in turn damage the cell: When x-ray photons are absorbed by water within a cell, free radical formation results.Free radicals combine to form toxins that damage cells.
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| injury, period of | Variety of cellular injuries may result
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| ionization | When x-rays strike pt tissue:Produced through photoelectric effect/Compton scatter; Results:formation of a +ve atom & dislodged neg. electron. Electron will interact w/ other atoms w/in absorbing tissues =ing chem.changes w/in the cell = biologic damage
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| latent period | Amount of time that elapses between exposure to ionizing radiation and the appearance of observable clinical signs; Depends on the total dose of radiation received and the amount of time it took to receive the dose
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| long-term effects | Small doses absorbed repeatedly over a long period of time;Effects seen after years, decades, or generations including Cancer, birth abnormalities, genetic defects
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| nonstochastic effects | There is a threshold; Severity increases with increasing absorbed dose; Examples: erythema, loss of hair, cataracts, and decreased fertility
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| radiation, background | Cosmic, Terrestrial
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| radiation absorbed dose (rad) | a unit for measuring absorbed dose; the traditional unit of dose equivalent to the gray (Gy); 100 erg of energy per gram of tissue; 100 rad=1 Gy
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| radioresistant | A cell that is resistant to radiation;Salivary glands,Kidney,Liver
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| radiosensitive | A cell that is sensitive to radiation; Lymphoid tissue, Bone marrow, Testes, Intestines
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| recovery period | Depending on a number of factors, cells can repair the damage caused by radiation
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| roentgen (R) | Measures radiation by determining the amount of ionization that occurs in air. Does not describe the amount of radiation absorbed
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| short-term effects | Associated with large doses of radiation in a short amount of time;Acute radiation syndrome (ARS) such as nausea, vomiting, diarrhea, hair loss, hemorrhage
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| somatic cells | all cells in the body except the reproductive cells
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| somatic effects | Seen in the person irradiated; Not seen in future generations
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| stochasitic effects | Direct function of the dose; No dose threshold; Not dependable on the magnitude of the absorbed dose; Examples: cancer and genetic mutations
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| inherent filtration | takes place when the primary beam passes through the glass window of the x-ray tube, the insulating oil, and the tubehead seal
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| added filtration | An aluminum disk is placed between the collimator and the tubehead seal; Filter out longer wavelength, lower energy x-rays from the x-ray beam; Filtration results in a higher-energy and more penetrating useful beam.
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| total filtration | sum of inherent and added filtration Regulated by state and federal law; Machines operating at or below 70 kVp require a minimum total of 1.5 mm. aluminum filtration;Machines operating above 70 kVp require a minimum total of 2.5 mm. aluminum filtration
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| collimation | Collimation restricts the size and shape of the x-ray beam; reduces patient exposure.
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| Maximum permissible dose (MPD) | Maximum dose that a body is permitted to receive in a specific period; MPD for occupationally exposed persons-5.0 rem/year; For non-occupationally exposed persons/pregnant occupationally exposed persons:0.1 rem/year
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| Maximum accumulated dose (MAD) | dose accumulated over a lifetime A formula based on the worker’s age: MAD = (N – 18) X 5 rem/year MAD = (N – 18) X 0.05 Sv/year
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| ALARA | as low as reasonably achievable. Every possible method of reducing exposure to radiation should be employed.
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| Distance | Distance traveled by x-ray beam affects intensity of beam.3 distances:Targ-surf. (srce to pt’s skin)Targ.-obj.(srce to pt’s tooth)Targ.-rec. (srce to rec.)As x-rays travel from pnt of orgn, they diverge to cover larger s.a.; intensity of beam lessens.
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| Density and Milliamperage | An increase in milliamperage: overall density of the radiograph. Results in a darker image
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