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)