Films Flashcards
What is the purpose of the emulsion layer? What is contained in it?
Mainly where image is captured.
Contains silver halide grains in a vehicle.
What is the convex and concave side facing during radiography?
Convex= radiation source Concave= Tongue
What is the purpose of the lead foil?
Positioned behind film to reduce exposure, reduce scattering, and indicate correct side of the film.
What does the black paper in film do?
Protects the light sensitive film inside.
What is used in extraoral films? What do they contain and why? At what cost?
Screen films.
Contain 2 intensifying screens that intensify the photon signal, needing less radiation to form an image. Because it sprays the photon out into many beams, image resolution is decreased.
Screen film is sensitive to what light? What is the process?
Visible light. Photon comes in, hits intensifying screen, turned into many different visible light rays.
What occurs during the formation of a latent image?
Silver bromide matrix contains sensitivity sites. x-ray ionized bromide, electron gets captured in sensitivity site, Ag is attracted to site and turns it into a neutral silver atom.
What does the developer do? What do you do after?
Neutral silver atoms act as a catalyst and react fast with the developer, turning into metallic silver grains. Wash away with water to prevent the non photon exposed changed from also reacting.
What does the fixer do?
Fixer washes away any non silver metallic grains (the grains that didn’t react with the developer).
What is chemical fog?
un-exposed silver halide grains are developed by chemical if left on too long.
What is optical density? How is it measured?
Degree of darkness.
Measured by how much light is transmitted. (so if 100% of light is transmitted, your OD is 0).
What increase optical density?
Increasing mA, or kVp (Increasing #/Energy means more can penetrate through, leading to dark areas).
Reducing x-ray source to receptor distance (closer it is, easier to penetrate through)
What happens to optical density with increased object thickness or density?
Optical density decreases with increased object thickness/density.
What is radiographic contrast? Low vs high?
Difference between light and dark areas.
Low=Long gray scale
High= Short gray scale.
What happens with contrast as you increase kVp?
Increase kVp= Lower contrast. Higher energy photons can keep reacting and penetrating, creating longer gray scale.
