After the films have been exposed, they need
to be processed. Even with the best placement technique, a cooperative
patient, and the highest quality x-ray machine, a film can be rendered
undiagnostic during processing.
X-ray film consists of a blue tinted plastic base covered
in an emulsion. The emulsion contains gelatin and silver halide crystals.
The silver halide crystals are energized by radiation exposure. When the
film is exposed to x rays, the energy reacts with the crystals and creates a
"latent image" depending on the different densities that the x-rays have
passed through. (The image is "latent" because it does not appear until the
film is developed.) Where there is a filling in the tooth, the halide crystals have
very little stored energy because the metal blocks out almost all the x-ray
beam. Conversely, interproximal spaces let most of the radiation through, so
the crystals in that area are full of stored energy and will precipitate on
the film base as black metalic silver particles when the film is developed. The ability for
different tissue densities to absorb radiation is called attenuation. Over
time the latent image will disappear, so it is best to process the film as
soon as possible after exposure. The film should be stored in a refrigerator
to slow attenuation if immediate processing is not possible.
When the x-ray is immersed in the developer
chemicals, it soaks into the gelatin and reacts with the silver halide
crystals. The energized crystals then form metallic silver and bromide. In
metallic form, tiny silver particles appear black. The
silver is deposited onto the film and causes the darker areas. The crystals
that were not energized are simply washed away by the fixer and that area of
the film remains white. So the developer reacts with the energized crystals
to make the black areas, and the fixer removes the unenergized crystals and
leaves those areas white. If the film comes out too dark, it is because it
is overexposed (too much radiation) or overdeveloped. If the film is too
light, it is underexposed, underdeveloped, or over fixed.
Most offices have an automatic processor and
tanks for quick processing. At some time in your career you may be called
upon to manually develop x-rays. The chemicals and theory are the same in an
automatic processor.
The most important factors to consider for
developing are the temperature of the chemical and the amount of time the
film is allowed to be in contact with the chemical. The higher the
temperature of the solution, the less time needed. The preferred condition
for manual processing is 4 1/2
to 5 minutes at 68ºF. Keep a nonmercury thermometer and a timer accurate in
minutes and seconds in the darkroom to check your solution.
After the film is submerged in the developer for
the proper amount of time, it must be rinsed in clean, circulating
water for 30 seconds. Then the film is submerged in the fixer for at least
10 minutes. The film is rinsed in a compartment with clean, running water
for at least 20 minutes to remove all the chemicals and silver. Then the
film can be hung to dry or a commercial drying machine or product can be
used.
It is imperative that the chemicals in the
darkroom are kept in the same order, developer in the first tank, water bath in the
center, and fixer in the third tank. The fixer will have a strong vinegary
smell. Stir the solutions before submerging the x-rays to mix and distribute
the temperature evenly. Use different instruments to stir the developer and
the fixer so the two aren't mixed. Make sure the liquid levels are adequate
to cover the films as they are dipped, and add the appropriate chemical if
necessary. The best temperature for the chemicals in manual processing is between 65ºF and 75ºF
(18ºC to 24ºC). Adjusting the temperature of the incoming water can regulate
this temperature. Given time, the chemicals will be the same temperature as
the water. The patient's name and date of exposure should be secured
somewhere on the rack. Make sure to turn off the overhead white light and
use the safe light. Clip the films firmly to the hanger. Use a timer, don't
rely on your memory. Rinse in between the solutions. The final wash should
be 20 to 30 minutes. If the films are in the water for more than an hour,
the emulsion may begin to wash off. If the films are left in water
overnight, they will be clear in the morning.
Chemicals should always
be handled according to the manufacturer's directions. The chemicals must be
checked every day and replenished as needed. Every day, six ounces of the
developer should be removed and replaced with six ounces of fresh developer.
Stir the solution to mix it well. The fixer should be replenished daily by
removing three ounces and replacing it with three ounces of fresh solution.
The chemicals must be completely changed according to the manufacturer's
directions. There are many factors that will determine when it is necessary,
to change over solutions, such as how many x-rays are developed, exposure of
the chemicals to air, and the amount of water dilution. The daily checker
film will be a good indicator of when to change the solutions.
The darkroom should be kept clean. The
chemical fumes could affect the emulsion of the film so store unused film in
another room. There should be plenty of room to work, especially next to the
processing tanks. The best internal temperature is 70ºF to 80ºF at 70%
humidity. It should be a totally dark room with no cracks in the door where
light might sneak in. To check for light leaks, enter the room and close the
door with the lights turned off. After your eyes have adjusted (2 or 3
minutes) look around for light. If you see any light leaks, they must be
sealed because it could effect the films during processing.
There should be hot and cold running water
near the tanks with mixing valves so the temperature can be regulated. A
white light source and a good quality safe light should be available at
least 4 feet away from the working surface.
Automatic film processors develop radiographs
more quickly than manual processing with consistently good results if the
chemicals are maintained. A series of rollers are inside the unit to guide
the film through the chemicals. The processor uses a heating element to keep
the solutions at a constant temperature, usually 85ºF to 105ºF. This higher
temperature shortens the time needed for processing. The action of the
rollers helps to disperse the chemicals evenly over the film. A special
roller at the end of each tank squeezes off most of the chemical so there is
no mixing or diluting of the chemicals.
The two most frequent causes of failure in
automatic processors are dirty rollers and expired chemicals. The chemicals
should be replenished at the beginning of the day. After four full mouth
surveys or panoramic films, the chemicals will need 4 to 6 ounces of new
solution. The rollers should be washed once a week with warm running water
and soaked for 10 to 15 minutes. Two large extraoral films should be run
through the machine to clean the rollers.
Depending on the rate of use, the solutions
should be changed every 2 to 6 weeks. Follow the guidelines and use the
solutions recommended by the manufacturer. Empty all the chemicals in an
orderly manner so they don't mix.
Follow the manufacturer's recommendations
carefully regarding lubrication, maintenance schedules, and general use. The
cover should be kept slightly ajar when the machine is not in use to let
fumes disperse and keep moisture from accumulating on the motor. Feed films
in at the recommended rate. Feeding too fast can cause them to stick
together.
X-ray films may need to be duplicated when
the patient moves, is referred to a specialist, for preauthorization of
insurance, or any other time a record of the x-rays needs to be sent outside
the office. The originals stay in the patient's chart as a permanent record
for the office. The operator can use double films (the type with two films
in the same packet) for x-rays that will be sent out. They yield two good
quality films while exposing the patient to the same amount of radiation.
Film duplicators can also be used, especially
when originals have already been taken. The duplicating film is sensitive to
light and becomes lighter when exposed. Regular x-ray film becomes darker
when exposed to light.
The duplicating procedure takes place in the
darkroom with safelights on. The radiographs to be copied are mounted in a
special mount designed for duplication with the embossed (raised) dot side
down for optimal contact with the duplicating film. Then these radiographs
are placed on the duplicator and the duplicating film is placed on top with
the emulsion side against the radiograph originals. Expose according to the
manufacturer's recommendations. The film is processed in the same way as
regular x-rays.
|
Dentists and allied dental professionals often
seek CE courses from ADA CERP recognized providers to fulfill their
CE requirements for re-licensure. Most state and
provincial licensing boards will accept CE credits issued by ADA
CERP recognized providers. In the spring of 2003, the FDI World
Dental Federation became the first internationally based CE provider
to be granted ADA CERP recognition.
Please contact your state board directly for their specific rules
and regulations. Most states approve supervised self-study courses
that are ADA CERP accredited.
Those dentists, hygienists, dental assistants
and radiographers interested in receiving 3 continuing
education credits for this course may take a 10 question test at a
cost of $35 and receive their certificate immediately by clicking
here.
Those dentists, hygienists, dental assistants
and radiographers interested in receiving 8 continuing
education credits for this course may take a 25 question test at a
cost of $66 and receive their certificate immediately by clicking
here.
Note: There are no questions on tables or
Glossary. |
