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32 Cards in this Set
- Front
- Back
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Who invented the fluoroscope in 1896?
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Thomas Edison
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What is used for examining moving internal structures and fluids?
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The fluoroscope.
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If less than 5 mA are used in fluorosocopy, why is it that pt dose is considerably higher during fluoroscopic exams than with radiographic exams which use hundreds of mA?
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In fluoroscopy, the x-ray beam exposes the pt for a considerably longer time.
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What is the principal advantage of image intensified fluoroscopy over earlier fluoroscopy?
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Increased image brightness.
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Which structures in the human eye are responsible for the sensation of vision?
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Rods and cones. Rods = night vision (scotopic); colorblind. Cones = daylight vision (photopic); can perceive color.
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The brightness of the fluoroscopic image depends primarily on what 3 things?
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Anatomy being examined, kVp and mA.
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When an x-ray interacts with the input phosphor, its energy is converted into what?
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Visible light.
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What component of the image intensifier emits electrons when illuminated by the input phosphor?
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The photocathode.
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What is electron emission following light stimulation?
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Photoemission.
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What is electron emission following heat stimulation?
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Thermionic emission.
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Which portion of the image intensifier do the electrons interact & produce light?
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The output phosphor.
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What is the ratio of light photons at the output phosphor to the number of x-rays at the input phosphor?
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Flux gain.
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What is the ability of the image intensifier to increase the illumination level of the image?
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Brightness gain.
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Increased magnification of image using magnification mode during fluoroscopy results in what?
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Decreased minification, ABC (automatic brightness control) increases mA consequently increasing pt dose (because mag'd images are dimmer).
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How wide is the input & output phosphor?
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Input phosphor: 5 - 12".
Output phosphor: 1/2 - 1". |
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What 3 things does magnification mode result in?
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Better contrast resolution, better spatial resolution, & higher pt dose.
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What is spatial resolution measured in?
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LP/MM = Line pairs per millimeter.
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What type of camera is most often used in television fluoroscopy?
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Vidicon.
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What does the tv camera tube do?
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It converts light image from the output phosphor to an electrical signal that is sent to the tv monitor, where it can be reconstructed as an image on the tv screen.
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What are some advantages of the tv camera tube?
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Can increase brightness level & controlled electronically without increased pt dose, as well as allow for storage of image in its electronic form.
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What does the target assembly of the vidicon consist of?
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Outside layer = faceplate/window.
Inside layer = signal plate which is a thin layer of metal/graphite. Photoconductive layer = Target made of antimony trisulfide. |
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What part of the target assembly of a vidicon conducts video signal out of the tube into the external video circuit?
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Signal plate.
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What part of the target assembly of a vidicon conducts electrons when illuminated and behaves as an insulator when dark?
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Target.
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What are the 5 ways that x-rays interact with matter?
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Coherent scatter, aka Thomspon, classical.
Compton effect. Photoelectric effect. Pair production. Photodisintegration. |
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Describe coherent scattering.
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AKA Thomspon, classical. X-rays has < 10 keV. Low energy. Little importance to radiology. Can reduce image contrast. Scatter energy = Incident energy, but scatters in different direction.
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Describe Compton effect.
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Occurs with moderate - high energies. Outer electron is ionized. Reduces image contrast. Source of occupational rad exposure (especially in fluoro). Incident energy > scatter energy and changes direction.
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Describe photoelectric effect.
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Occurs with low - moderate energies. Affects inner shell electron, producing characteristic x-ray production after photoelectric interaction.
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Describe pair production.
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Doesn't occur during x-ray imaging. Needs 1.02 MeV to occur. Affects nuclear electric field. X-ray disappears. 2 electrons appear: a positively charged positron and a negatively charged negatron.
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Describe photodisintegration.
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Doesn't occur in diagnostic radiology. Needs 10 MeV to occur. Nucleon is emitted from nucleus.
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What are 2 important ways that x-rays can interact with tissue?
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Compton (occupational dose) and photoelectric effect (pt dose).
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What are 2 methods of x-ray production important to radiography?
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Bremstrahlung (braking) and characteristic (k-shell knockout).
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What is the difference in x-ray interaction called?
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Differential absorption, which increases when kVp is decreased to obtain short-scale images. However, this results in higher pt dose.
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