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RAD 254 Chapter 11Radiographic Film/Receptor
Image forming rays: remnant beam/exit radiation – scattered radiation (partially
absorbed) and non-interacting
Rad Film – 2 main parts: emulsion and base
• Base: rigid, non-shrinking base to support the emulsion now made of polyester
• Emulsion: Silver halide and gelatin. 98% is silver bromide, the rest is usually silver iodide
Latent Image
• Produced when 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)
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, Duplicating, Spot Film, Subtraction, and Cine
Direct exposure
• Non-screen film sensitive to x-rays– Like “bite wings” at the dentist
Screen Film – sensitive to both light and radiation
• Comes in a variety of contrast, latitude, speed and light color sensitivity
• Larger silver halide crystals = faster speed, less detail
• Thicker emulsion layer = faster speed, less detail
• Double emulsion layer = faster speed, prone to “crossover”
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 mainly in the 50’s (57-71)
• Orthochromatic = green sensitive film• Panchromatic = sensitive to all color
(photographic film)• Laser = sensitive to red light
Other type films
• Mammo/routine films = some mammo is single emulsion and single screen film and some double/double
• Duplicating film = single emulsion, /solarized film
• Cine = Dynamic motion (heart caths, etc) 35mm
• Spot film camera film = 70mm, 105 mm
Safelights
• Filter is spectral matched to filter out the light spectrum the film is SENSITIVE TO (wratton 6-B – red safelite 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)
Film Storage
• Boxes to be stored on end – NEVER flat
• 68F (20C) best at 50F(10C) AND low humidity (40 percent 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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