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34 Cards in this Set
- Front
- Back
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Radiographic films have a contrast gradient of ____ while mammography films have a gradient of ____.
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2; > 3
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What is the latittude (dynamic range) of film
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40:1
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Why does breast compression allow the use of high contrast film in mammography?
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Reduces variation in air kerma, so permits use of high contrast film
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____ photon energies result in high subject contrast.
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Low
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What is the atomic number of Ba?
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56
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What is the K-edge of Barium?
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37 keV
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What is the atomic number of iodine?
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53
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What is the K-edge of iodine?
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33 keV
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What is the resolution of the human eye?
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5 lp / mm at 25 cm (30 lp / mm on close inspection)
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What is the limiting spatial resolution in digital chest radiography vs. screen-film mammography?
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3 vs 15 lp /mm
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What is the limiting spatial resolution of digital versus screen-film chest radiography?
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3 vs 5 lp / mm
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What is the focal spot blur in contact radiography?
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There is no focal spot blur
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What is the focal spot in angiogram magnification?
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0.3 mm
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What is the relationship between FWHM and LSF?
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FWHM ~ 1/(2 x LSF)
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What is the FWHM of a line spread function of 0.1 mm?
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~ 5 lp /mm
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What is the limiting spatial resolution of film alone?
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100 lp/mm
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What is the limiting screen-film resolution (200 speed)?
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5 lp / mm
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What is the limiting screen film resolution of mammography?
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15 lp / mm
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What is the ACR requirement for screen-film resolution?
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11 to 13 lp/mm
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What is the theoretical vertical resolution of a 525 line TV system when displaying a 250 mm object
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1 lp / mm
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What percent of theoretical TV resolution is achieved?
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70%
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What is the ratio of actual to theoretical resolution in TV called?
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Kell factor
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What ist he typical TV Kell factor?
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0.7
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Horizontal resolution of TV is determined by what?
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Bandwidth
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What is the bandwidth of a 525 line TV system?
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5 MHz
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What is the bandwidth of a 1000 line TV system?
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20 MHz
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What is the focal spot blur in fluoroscopy?
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Negligible
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What is the limiting resolution of an image intensifier?
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5 lp / mm
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What does halving the II FOV electronically do to resolution?
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Halves it
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What does reducing the II FOV through collimation do to resolution?
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Nothing
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What is pitch?
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1 / (sampling frequency)
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What is the matrix size of chest x-ray?
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2k x 2.5k
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What is the sampling frequency of chest x-ray?
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5.7 per mm, 350 mm / 2k
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What is the matrix size in digital fluoroscopy?
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1k x 1k
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