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RAD 354 Chapt 12 Screen- FilmRadiography

RAD 354 Chapt 12 Screen- FilmRadiography. Image forming rays: remnant beam/exit radiation – scattered radiation (partially absorbed/attenuated) and non-interacting. X-ray beam. RAD Film – 2 main parts: emulsion and base.

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RAD 354 Chapt 12 Screen- FilmRadiography

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  1. RAD 354 Chapt 12Screen-FilmRadiography • Image forming rays: remnant beam/exit radiation – scattered radiation (partially absorbed/attenuated) and non-interacting

  2. X-ray beam

  3. RAD Film – 2 main parts: emulsion and base • Base: rigid, non-shrinking base to support the emulsion – now made of plyester • Emulsion: Silver halide and gelatin. 98% is silver bromide, the rest is usually silver iodide

  4. Latent Image • Produced when the exit beam (remnant beam) exists the patient and interacts with the emulsion/image receptor • Takes place at the sensitivity spec (center) due to liberated charges traveling in the development center (spec or receptor)

  5. Film/Receptor Types • Digital – • Computed Radiography (CR) = Photostimulable Phosphor (PSP) • Direct Radiography (DR/DDR) = Solid State X-ray Detector (SSXD) • Film: Screen, Direct Exposure, Mammo, Laser, Duplication, Spot Film, Subtraction and Cine

  6. Direct Exposure • Non-screen film – sensitive to x-rays • Like “bite wings” at the dentist

  7. Screen Film – sensitive to both light and radiation • Comes in a variety of contrast, latitude, spee and light color sensitivity • Larger silver halide crystals = faster speed and LESS DETAIL • Thick emulsion layer = faster speed and LESS DETAIL • Double emulsion layer – faster speed – prone to “CROSSOVER”

  8. COLOR SENSITIVITY • Spectral matching = matching the color spectrum of light given off by screens to that of the emulsion • Calcium Tungstate Crystals (atomic #’s 60/70’s) • Rare Earth – AMU’s mainly in the 50’s (57-71) • Orthochromatic = green sensitive film • Panchromatic = sensitive to all color (photographic film) • Laser = sensitive to red light

  9. Other type films • Mammo/routine films = some mammo is single emulsion and single screen film and some double/double • Duplicating film – single emulsion, solaraized film • Cine = Dynamic motion (heart caths, etc.) 35mm • Spot film camera film = 70mm, 105mm

  10. Darkroom Safelights • Filter is spectral matched to filter out the light spectrum the film is SENSITIVE to (wratten 6-B = red safelight filter) • Usually 15 watt bulb • Should be no closer than 5 feet from work surface (some “feed trays” have a safelight that turns on after the film has progressed into the processor and out when a film begins to enter the processor)

  11. Film Storage • Boxes to be stored on end – NEVER flat! • 68F (20C) best at 50F (1-C) AND low humidity (40% or LESS) • Unexposed film is MUCH less sensitive to light, radiation, chemicals, heat, etc., than EXPOSED FILM! • Shelf life – limited (film begins to develop as soon as it is made)

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