Transcript RAD 354 Chapt 11 Radiographic Film/Receptor

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
• 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
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)
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
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, 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”
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
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
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)
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)