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25 Cards in this Set
- Front
- Back
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density = ?
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the overall degree of darkening of exposed film
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density is dependent on _______________________
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the number of photons striking the film
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factors that affect density
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- exposure time
- milliamperage - kilovoltage peak - subject thickness - object density |
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thin image =
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too light
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dense image =
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too dark
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contrast = ?
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the difference in densities between various regions on a radiograph
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describe high contrast
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very dark and very light
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describe low contrast
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many shades of gray
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factors affecting contrast
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- subject thickness, density and atomic number
- beam energy and intensity - fog and scatter - film sensitivity |
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how does kVp affect contrast
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a decrease in kVp produces a decrease in effective energy of the x-ray beam, resulting in increased contrast
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what is high contrast good for
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visualizing large differences in density, e.g. caries
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what is low contrast good for
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discrimination of smaller differences in density
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sharpness = ?
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measures how well minimum details of an object are reproduced
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sharpness is due to ______________
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the penumbra around the object
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4 things that affect sharpness
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- size of focal spot
- double emulsion - target to object distance - object to film distance |
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how do you increase sharpness
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- decrease size of effective focal spot (decrease angulation of target)
- increase distance from target to object - decrease distance from object to film |
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as you decrease distance from object to film, what happens to penumbra and magnification
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they are decreased
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resolution = ?
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a measure of how well two close, small images are visualized
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the intensity of an x-ray beam is ______________________________
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inversely proportional to the square of the distance between the focal spot and the point of measure
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what happens to intensity of an x-ray beam if you double the distance the beam has to travel
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it is reduced by 1/4th
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describe the relationship of the film, long axis of the tooth and x-ray beam to get a nice image
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film and long axis are parallel, while the beam is perpendicular to both
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what happens if there is an angle between the film and the long axis of the tooth, with the photon beam perpendicular to the film
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foreshortening
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what happens if there is an angle between the film and the long axis of the tooth with the photon beam perpendicular to the long axis
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elongation
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elongation usually occurs when ______________________
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you don't use the rinn kit
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what is the SLOB rule
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when you can't tell on the radiograph if an object is on the facial or lingual, you take a second image, do the distal or mesial. if the object travels in the same direction, it's on the lingual. if it travels the opposite direction it's on the buccal.
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