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205 Cards in this Set
- Front
- Back
Chemical, usually acetic acid in the fixer and sodium carbonate in the developer, used to neutralize the developer and swell the gelatin. |
Activator
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Phosphorescence in an intensifying screen.
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Afterglow |
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Practice of moving the image receptor 10 to 15 cm from the patient so that fewer scattered x-rays interact with the image receptor, thereby enhancing contrast.
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Air-gap technique
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Computer-adapted mathematical calculation applied to raw data during image reconstruction.
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Algorithm |
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Technique by which graphics on the console guide the technologist in selection of a desired kVp and mAs
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Anatomically programmed radiography (APR)
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Circular opening for the patient in the gantry of a computed tomographic or magnetic resonance imaging system. b. Fixed collimation of a diagnostic x-ray tube, as in an aperture diaphragm. c. Variable opening before the lens of a cine or photospot camera.
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Aperture |
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Simple beam-restricting device that attaches a lead-lined metal diaphragm to the head of the x-ray tube.
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Aperture diaphragm
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X-ray beam pattern that usually is shaped like a square or a rectangle, and that is used in conventional radiography and fluoroscopy
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Area beam
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Part of a computer that handles raw data and performs the mathematical calculations necessary to reconstruct a digital image.
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Array processor
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Reduction in radiation intensity that results from absorption and scattering.
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Attenuation
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Feature that determines radiation exposure during radiography in most x-ray imaging systems.
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Automatic exposure control (AEC)
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Measure of radiographic contrast.
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Average gradient
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X-rays that have interacted with an object and are deflected backward.
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Backscatter radiation |
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Area that serves as a mechanical support for the active phosphor layer in a radiographic intensifying screen.
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Base
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Optical density inherent in the base of the film.
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Base density
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Average density from an unexposed area of the strips.
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Base plus fog (B+F)
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Device that provides a means of restricting the size of an x-ray field.
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Beam-limiting device
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Ability of an x-ray beam to penetrate tissue
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Beam penetrability
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Device that restricts the size of the x-ray field to only the anatomic structure of interest.
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Beam restrictor
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Number of bits used to reproduce image gray levels (e.g., 8 bits=28 =256 gray levels).
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Bit depth
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Ability of the image intensifier to increase the illumination level of the image.
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Brightness gain
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Alkali compound in the developer that enhances the action of the developing agent by controlling the concentration of hydrogen ions.
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Buffering agent
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Instrument with two bent or curved legs used for measuring the thickness of a solid.
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Calipers
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Rigid holder that contains the film and screens.
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Cassette
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X-ray beam composed of x-rays that travel along the center of the useful x-ray beam.
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Central axis x-ray beam
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Processing hardware in large computers.
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Central processing unit (CPU)
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Center of the x-ray beam that interacts with the image receptor.
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Central ray
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Graph of optical density versus log relative response; H & D curve
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Characteristic curve
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Solid-state device that converts visible light photons to electrons.
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Charge-coupled device (CCD)
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Artifact produced by chemical contamination of the developer.
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Chemical fog
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A chemical, usually ammonium thiosulfate, that is added to the fixer to remove undeveloped silver bromine from the emulsion.
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Clearing agent
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Restriction of the useful x-ray beam to reduce patient dose and improve image contrast.
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Collimation
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Material inserted between an x-ray source and a patient to shape the intensity of the x-ray beam. An x-ray beam filter is designed to make the remnant beam more uniform in intensity.
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Compensating filter
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The act of flattening soft tissue to improve optical density
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Compression
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Radiographic technique that uses a photostimulable phosphor as the image receptor and an area beam.
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Computed radiography (CR)
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Circular metal tube that attaches to x-ray tube housing to limit the beam size and shape.
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Cone
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Misalignment of cones that causes one side of the radiograph to not be exposed because the edge of the cone may interfere with the x-ray beam.
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Cone cutting
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Degree of difference between the light and dark areas of a radiograph
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Contrast
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Ratio of radiographic contrast with a grid to that without a grid.
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Contrast improvement factor
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Difference between the step with an average optical density closest to 2.2 and the step with an average optical density closest to, but not less than, 0.5.
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Contrast index
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Agent that enhances differences between anatomic structures.
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Contrast medium
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Ability to distinguish between and to image similar tissues.
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Contrast resolution
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Rate at which x-ray energy is transformed into light in an intensifying screen.
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Conversion efficiency (CE)
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Grid on which lead strips run parallel to the long and short axes.
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Crossed grid
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Instrument that measures the optical density of exposed film.
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Densitometer
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The difference between the step with an average optical density closest to 2.2 and the step with an average optical density closest to, but not less than, 0.5.
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Density difference (DD)
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Degree of sharpness of structural lines on a radiograph.
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Detail
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Percentage of x-rays absorbed by the screen by the image receptor.
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Detective quantum efficiency (DQE)
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Stage of processing during which the latent image is converted to a manifest image.
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Developing
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A chemical, usually phenidone, hydroquinone, or Metol, that reduces exposed silver ions to atomic silver.
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Developing agent
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Artifact that results from reduction of crystals that had not been exposed to metallic silver caused by the lack of a restrainer.
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Development fog
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Different degrees of absorption in different tissues that result in image contrast and formation of the x-ray image.
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Differential absorption
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Static images produced with a fan x-ray beam intercepted by a linear array of radiation detectors or an area x-ray beam intercepted by a photostimulable phosphor plate or a direct-capture solid-state device.
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Digital radiography (DR)
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Film used without intensifying screens
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Direct-exposure film
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Unequal magnification of different portions of the same object.
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Distortion
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Radiographic film that has an emulsion coating on both sides of the base and a layer of supercoat over each emulsion.
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Double-emulsion film
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Single-emulsion film that is exposed to ultraviolet light or blue light through the existing radiograph to produce a copy
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Duplicating film
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Range of values that can be displayed by an imaging system; shades of gray.
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Dynamic range
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Accentuation of the interface between different tissues.
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Edge enhancement
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Area projected onto the patient and the image receptor.
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Effective focal-spot size
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Image that is made to appear longer than it really is because the inclined object is not located on the central x-ray beam.
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Elongation
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Material with which x-rays or light photons from screens interact and transfer information.
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Emulsion
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X-rays that remain after the beam exits through the patient.
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Exit radiation
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Factors that influence and determine the quantity and quality of x-radiation to which the patient is exposed.
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Exposure factors
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Electrons that bounce off the focal spot and land on other areas of the target.
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Extrafocal radiation, off-focus radiation
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Image matrix size provided by digital x-ray imaging systems.
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Field of view (FOV)
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Principle that states that if the optical density on a radiograph is to be increased with the use of kVp, an increase in kVp by 15% is equivalent to doubling of the mAs.
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Fifteen percent rule
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Distribution of silver halide grains in an emulsion.
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Film graininess
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Removal of low-energy x-rays from the useful beam with aluminum or another metal. It results in increased beam quality and reduced patient dose.
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Filtration
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Principle that states that an increase of 5% in the kVp may be accompanied by a 30% reduction in the mAs to produce the same optical density at a slightly reduced contrast scale.
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Five-percent rule
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Stage of processing during which the silver halide not exposed to radiation is dissolved and removed from the emulsion.
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Fixing
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Emission of visible light only during stimulation.
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Fluorescence
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Imaging modality that provides a continuous image of the motion of internal structures while the x-ray tube is energized. Real-time imaging.
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Fluoroscopy
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Region of the anode target in which electrons interact to produce x-rays.
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Focal spot
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Blurred region on the radiograph over which the technologist has little control.
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Focal-spot blur
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Radiographic grid constructed so that the grid strips converge on an imaginary line.
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Focused grid
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Unintended optical density on a radiograph that reduces contrast through light or chemical contamination.
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Fog
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Development of silver grain that contains no useful information.
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Fog density
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Reduction in image size; related to the angle of inclination of the object.
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Foreshortening
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Part of the emulsion that provides mechanical support for the silver halide crystals by holding them uniformly dispersed in place.
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Gelatin
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Slope of the tangent at any point on the characteristic curve.
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Gradient
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Image display in which intensity is recorded as variations in brightness.
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Gray scale
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Device used to reduce the intensity of scatter radiation in the remnant x-ray beam.
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Grid
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Ability of a grid to absorb scatter radiation
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Grid cleanup
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Absence of optical density on a radiograph caused by unintended x-ray absorption in a grid.
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Grid cutoff
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Number of grid lines per inch or centimeter
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Grid frequency
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Series of sections of radiopaque material.
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Grid lines
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Ratio of grid height to grid strip separation
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Grid ratio
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Reflection of screen light transmitted through the emulsion and base.
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Halation
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Permanent image on film or paper, as opposed to an image on a cathode ray tube, a disc, or magnetic tape.
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Hard copy
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A chemical, usually potassium glutaraldehyde alum in the fixer, that is used to stiffen and shrink the emulsion.
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Hardener
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X-ray that has high penetrability and therefore is of high quality
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Hard x-ray
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Absorption of x-rays in the heel of the target, resulting in reduced x-ray intensity to the anode side of the central axis.
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Heel effect
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Ability to image small objects with high subject contrast; spatial resolution.
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High-contrast resolution
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Sharpness of small structures on the radiograph.
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Image Detail
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Layout of cells in rows and columns
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Image matrix
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Deterioration of the radiographic image.
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Image noise
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Medium that transforms the x-ray beam into a visible image; radiographic film or a phosphorescent screen.
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Image receptor (IR)
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Ratio of exposure without screens to that with screens to produce the same optical density.
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Intensification factor (IF)
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Hardware and software that enable imaging systems to interconnect and to connect with printers.
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Interface
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Time during which the signal from an image detector is sampled
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Interrogation time
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Sections of radiolucent material in a grid.
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Interspace material
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Law that states that the intensity of radiation at a location is inversely proportional to the square of its distance from the source of radiation.
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Inverse square law
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Equal intensity in all directions; having the same properties in all directions.
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Isotropic
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Unobservable image stored in the silver halide emulsion; it is made manifest by processing.
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Latent image
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Sensitivity center that has many silver ions attracted to it.
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Latent image center
(sensitivity speck) |
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Improper positioning of the grid that results in cutoff.
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Lateral decentering
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Range of x-ray exposure over which a radiograph is acceptable.
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Latitude
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Design incorporated into x-ray tube targets to allow a large area for heating while a small focal spot is maintained.
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Line focus
principle |
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Change in optical density over each exposure interval.
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Log relative exposure (LRE)
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Low-contrast radiograph that has many shades of gray.
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Long gray scale
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Matrix of data that manipulates the values of gray levels, converting an image input value to a different output value.
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Look-up table (LUT)
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Ability to image objects with similar subject contrast.
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Low-contrast resolution
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Emission of visible light
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Luminescence
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The observable image that is formed when the latent image undergoes proper chemical processing.
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Manifest image
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Rows and columns of pixels displayed on a digital image.
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Matrix
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Reconstruction of an image through selection of the highest-value pixels along any arbitrary line in the data set; only those pixels are exhibited.
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Maximum-intensity projection (MIP)
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Product of exposure time and x-ray tube current; measure of the total number of electrons
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Milliampere-second (mAs)
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Blurring of the image that results from movement of the patient or the x-ray tube during exposure
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Motion blur
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a. Grainy or uneven appearance of an image caused by an insufficient number of primary x-rays. b. Uniform signal produced by scattered x-rays.
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Noise
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Distance from the image receptor to the object that is to be imaged.
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Object-to-image receptor distance (OID)
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Artifact produced by an improperly positioned radiographic tube—not by an improperly positioned grid.
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Off-level grid
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Surface that does not allow the passage of light.
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Opaque
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Degree of blackening of a radiograph
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Optical density
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Referring to blue- or green-sensitive film; usually exposed with rare Earth screen.
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Orthochromatic
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Referring to a radiograph that is too dark because too much x-radiation reached the image receptor.
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Overexposed
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Referring to film that is sensitive to the entire visible light spectrum.
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Panchromatic
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Ability of an x-ray to penetrate tissue; range in tissue; x-ray quality.
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Penetrability
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Image blur that results from the size of the focal spot; geometric unsharpness
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Penumbra
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Active layer of the radiographic intensifying screen closest to the radiographic film.
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Phosphor
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Emission of visible light during and after stimulation.
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Phosphorescence
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Device that allows automatic exposure control.
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Phototimer
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Picture element; the cell of a digital image matrix.
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Pixel
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Chemical treatment of the emulsion of a radiographic film to change a latent image to a manifest image.
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Processing
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Layer of the radiographic intensifying screen closest to the radiographic film
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Protective coating
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Radiographic noise produced by the random interaction of x-rays with an intensifying screen. This effect is more noticeable when very high rare Earth systems are used at a high kVp.
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Quantum mottle
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Artifact caused by unintentional exposure to radiation.
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Radiation fog
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Relative penetrability of an x-ray beam determined by its average energy; usually measured by half-value layer or kilovolt peak.
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Radiation quality
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Intensity of radiation; usually measured in milliroentgen (mR).
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Radiation quantity
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Combined result of image receptor contrast and subject contrast.
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Radiographic contrast
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Device that converts the energy of the x-ray beam into visible light to increase the brightness of an x-ray image.
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Radiographic intensifying screen
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Undesirable fluctuation in the optical density of the image.
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Radiographic noise
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Combination of settings selected on the control panel of the x-ray imaging system to produce a quality image on the radiograph.
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Radiographic technique
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Guide that describes standard methods for consistently producing high-quality images.
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Radiographic Technique Chart
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Radiographic noise produced by the random interaction of x-rays with an intensifying screen. This effect is more noticeable when very high rare Earth systems are used at a high kVp.
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Quantum mottle
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Artifact caused by unintentional exposure to radiation.
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Radiation fog
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Relative penetrability of an x-ray beam determined by its average energy; usually measured by half-value layer or kilovolt peak.
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Radiation quality
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Intensity of radiation; usually measured in milliroentgen (mR).
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Radiation quantity
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Combined result of image receptor contrast and subject contrast.
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Radiographic contrast
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Device that converts the energy of the x-ray beam into visible light to increase the brightness of an x-ray image.
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Radiographic intensifying screen
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Undesirable fluctuation in the optical density of the image.
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Radiographic noise
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Combination of settings selected on the control panel of the x-ray imaging system to produce a quality image on the radiograph.
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Radiographic technique
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Guide that describes standard methods for consistently producing high-quality images.
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Radiographic Technique Chart
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Referring to a tissue or material that transmits x-rays and appears dark on a radiograph.
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Radiolucent
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Referring to a tissue or material that absorbs x-rays and appears bright on a radiograph.
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Radiopaque
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Radiographic intensifying screen made from rare Earth elements, which make it more useful for radiographic imaging.
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Rare Earth screen
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Principle that states that optical density on a radiograph is proportional only to the total energy imparted to the radiographic film.
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Reciprocity law
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Creation of an image from data
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Reconstruction
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Time needed for the computer to present a digital image after an examination has been completed.
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Reconstruction time
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Degree of sharpness of structural lines on a radiograph.
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Recorded detail
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Filter that transmits light only above 600 nm; it is used with both green- and blue-sensitive film.
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Red filter
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Chemical responsible for reduction.
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Reducing agent
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Layer of the intensifying screen that intercepts light headed in other directions and redirects it to the film.
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Reflective layer
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Area of an anatomic structure on a reconstructed digital image as defined by the operator using a cursor.
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Region of interest (ROI)
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X-rays that pass through the patient and interact with the image receptor.
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Remnant radiation
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Replacement of developer and of fixer in the automatic processing of film.
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Replenishment
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Measure of the ability of a system to image two separate objects and visually distinguish one from the other.
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Resolution
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Compound that restricts the action of the developing agent to only irradiated silver halide crystals.
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Restrainer
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Incandescent lamp with a color filter that provides sufficient illumination in the darkroom while ensuring that the film remains unexposed.
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Safelight
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X-rays scattered back in the direction of the incident x-ray beam.
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Scatter radiation
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The phosphorescence in an intensifying screen.
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Screen lag
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Relative number used to identify the efficiency of conversion of x-rays into usable light.
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Screen speed
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The most commonly used film; used with intensifying screens
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Screen-film
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Ratio of primary radiation to scattered radiation transmitted through the grid.
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Selectivity
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Ability of an image receptor to respond to x-rays.
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Sensitivity
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Physical imperfections in the lattice of the emulsion layer that occur during the film manufacturing process.
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Sensitivity center (speck)
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Optical step wedge that is used to construct a characteristic curve.
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Sensitometer
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Study of the response of an image receptor to x-rays
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Sensitometry
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Type of distortion caused by elongation or foreshortening.
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Shape distortion
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High-contrast radiograph that exhibits black to white in just a few apparent steps.
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Short gray scale
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Material that makes up 98% of the silver halide crystals in a typical emulsion
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Silver bromide
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Active ingredient of the radiographic emulsion. It is instrumental in creating a latent image on the radiograph
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Silver halide crystals
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Material that makes up 2% of the silver halide crystals in a typical emulsion.
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Silver iodide
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Output on a display screen.
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Soft copy
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X-ray that has low penetrability and therefore is of low quality.
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Soft x-ray
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Distance from the x-ray tube to the image receptor.
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Source-to-image receptor distance (SID)
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Misrepresentation in the image of the actual spatial relationships among objects.
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Spatial distortion
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Measure of resolution; usually expressed in line pairs per millimeter (lp/mm).
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Spatial frequency
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Constancy of pixel values in all regions of the reconstructed image
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Spatial uniformity
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Use of rare Earth screens only in conjunction with film emulsions that have light absorption characteristics matched to the light emission of the screen.
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Spectrum matching
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Term used to loosely describe the sensitivity of film to x-rays.
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Speed
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Principle that states that one can compensate for a change in the source-to-object distance by changing the mAs by the factor SID squared.
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Square law
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Portion of a sensitometric curve in which the diagnostic or most useful range of density is produced.
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Straight-line portion
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Distribution of phosphor crystals in an intensifying screen.
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Structure mottle
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Component of radiographic contrast determined by the size, shape, and x-ray attenuating characteristics of the subject who is being examined and the energy of the x-ray beam. See also Image receptor contrast.
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Subject contrast
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The kVp and mA as selected for a given radiographic examination.
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Technique factors
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Referring to a radiograph that is too light because too little x-radiation reaches the image receptor.
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Underexposed
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Primary radiation used to form an image.
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Useful beam
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Box-shaped device that contains a radiographic beam–defining system. It is the device that is most often used to reduce the size and shape of a radiographic beam.
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Variable aperture collimator
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Stage of processing during which any remaining chemicals are removed from the film.
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Washing
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Agent, usually water, that treats the radiograph so that chemicals can penetrate the emulsion.
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Wetting agent
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Location on a digital image number scale at which the levels of grays are assigned. It regulates the optical density of the displayed image and identifies the type of tissue to be imaged.
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Window level
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Specific number of gray levels or digital image numbers assigned to an image. It determines the grayscale rendition of the imaged tissue and therefore the image contrast.
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Window width
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Penetrability of an x-ray beam.
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X-ray quality
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Output intensity of an x-ray imaging system; measured in roentgens (R).
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X-ray quantity
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