Intensifying screens are sheets of luminescent phosphor crystals bound
together and mounted on a polymer or plastic base. Two screens are
normally inside the cassette to sandwich the x-ray film, which has a
coating of light-sensitive emulsion on both sides (double emulsion).
When the phosphor crystals in the screen are struck by the x-ray, the
crystals fluoresce, whereby x-rays are converted into visible light that
exposes the film. The primary purpose of the screens is to reduce the
amount of radiation exposure required to produce a diagnostic
radiograph.
Screen Characteristics
The use of screens decreases the amount of radiation to
the patient, the radiographer and decreases voluntary and involuntary
motion on the film. Four properties determine the efficiency of the
screen material: 1. Intensifying screens must have a high x-ray
absorption. 2. Intensifying screens must have a high x-ray to light
conversion with suitable energy and color. 3. There must be little or no
“afterglow” after radiation has ceased. (afterglow=the tendency of
phosphor to continue to give off light after the x-ray exposure has
stopped). 4. The phosphor size and type, Green, Blue Rare Earth and
non-Rare Earth.
Screen Light Output Types
The first phosphor intensifying screen was made of
calcium tungstate was chosen for its emission of light in the blue
regions of the ultraviolet spectrum which had a high sensitivity of
silver halide (within the film emulsion) to this spectrum of light.
Calcium tungstate has a relatively high absorption ability and is
physically strong, but is lacking in light conversion efficiency. In
1972, new phosphor technology developed the blue rare-earth system
having greater speed. The “rare-earth” group is also known as the
lanthanide series because it consists of elements having atomic numbers
57 (lanthanum) through 71 (lutetium). The x-ray to light conversion
efficiency of rare-earth phosphors is significantly greater than that of
calcium tungstate. The light conversion is four (4) times as great. The
spectral emission of the newest rare-earth phosphors is in the green
light part of the visible light spectrum. Because the standard x-ray
silver halide film will not absorb (i.e., is not sensitive to) light in
the green area, a special film that is sensitive to the green spectrum
of light must be employed with this type of screen. Green Rare-Earth
screen/film systems are the most common system used in veterinary
radiography today. One of the most popular rare-earth system on the
market today are supplied by DIS/AGFA. Using portable or stationary
x-ray equipment a DIS Rare-earth film and cassette/screen combination
address the needs of veterinarians by allowing them to acquire
radiographs with shorter exposure times and greater detail without
compromising image quality.
| CASSETTES |
Easy handling high-impact Aluminum, Polymer or
use Vinyl, Red Rigid Ultra Lightweight cassettes for field use
in large quantities. Polymer Cassettes are durable yet
lightweight, will not dent and designed to provide superior
film/screen contact and are easy to clean. |
| RARE EARTH GREEN SCREENS |
These most popular Green Emitting Regular and
Asymmetric Screens utilize the Rare-Earth phosphor Gadolinium
Oxysulfide, for use with orthochromatic, green sensitive film.
Speeds: Green 600, Green 400, Green 200, Green 100, Green 50
speed. |
|
RARE EARTH BLUE SCREENS |
These Blue Emitting Screens developed in the
70’s are made with Rare-Earth phosphors for use with blue
sensitive film. Speeds: Blue 800, Blue 400, Blue 100 speed.
|
|
CALCIUM TUNGSTATE |
These older technology NON-RE Calcium Tungstate
Screens are manufactured using carefully selected and controlled
calcium tungstate phosphors applied to a polyester base. Speeds:
Hi Plus 200, Medium 100, Fine 50 Speed. |
|
AGFA/DIS Deluxe Lightweight Cassette GREEN RE
Film/Screen Combination Speeds |
| 50 Speed |
Detail Film/Detail Cassettes: DIS G50 Detail
Film/G100 Deluxe Cassette/Screens |
| 100 Speed |
Regular Film/Detail Cassettes: DIS G400
Regular Film/G100 Deluxe Cassette/Screens |
| 200 Speed |
Detail Film/Regular Cassettes: DIS G50 Detail
Film/G400 Cassettes/Screens or DIS G400/G200 Al. Cass./Screens |
| 400 Speed |
Regular Film/Regular Cassettes: DIS G400
Regular Film/G400 Cassette/Screens |
| 600 Speed |
Regular Film/High speed Cassettes: DIS G400
Regular Film/G600 Al. Cassette/Screens |
|
AGFA/DIS Deluxe Lightweight Cassette BLUE RE Film/Screen
Combination Speeds |
| 200 Speed |
Detail Film/Regular Cassettes: G50 Detail
Film/B800 Cassettes/Screens |
| 400 Speed |
Half Speed Film/Regular Cassettes: B400
Film/B800 Cassettes/Screens |
| 800 Speed |
Regular Film/Regular Cassettes: B800 Film/B800
Cassettes/screens |
| 1-800-346-9729 |
www.vetxray.com |
Sales@vetxray.com |
Diagnostic Imaging Systems,
Inc.
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