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Lecture7 17-march-2013
Dental x-ray film processing
The exam material: from chapter 1 to chapter 9.The reference for the exam is your text book. Everyone
should seat on his/her seat number.
The Dr said that the exam will be easy but study well.
The Dr covered chapter 8 indirectly in the first lecture, so this lecture is from chapter 9 (Dental X-ray film
processing).
After exposure we have to process the film in order to see image, film processing
has a series of steps that collectively convert a latent image into a permanent visible
image.
Actually, we do not always need to do processing, because we have digital units
which dont need film processing, for this reason nowadays in many universities they
stop giving this lecture, because we are in era of digital image, no need for
processing. However, because you are going to do processing, you have to learn
about it.
So latent image is better/or pattern (not sure) form of emulsion that cant be seen or
detected, only seen after chemical processing of the film; processing means
developing and fixing.
This is the latent image, after it becomes a visible image.(I dont know what is the
pic!).
Formation
How operating image will be formed? You know the emulsion contains silver
halide crystals; bromide and iodide, it depends on the type of the film, if its F speed
or D speed. Silver crystals will absorb the x-ray, x-rays are high energy photons, soitll ionize silver bromine crystals (or iodine), and the atoms are separated so now we
have ions, silver atoms will aggregate in irregularities of the crystals called
sensitivity space .So this is a kind of store energy.
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Processing
To process the film we have to follow five steps mainly if its a manual processing:1. Development.
2. Rinsing.
3. Fixing.
4. Washing.
5. Drying.
What we do here (I think its the clinic) is automatic processing not manual
processing and you have to differentiate between these two types.
Latent image formation:
If its a soft tissue mostly all of the X-ray will penetrate and expose the crystals, if
it is bone few x-rays penetrate, if its amalgam or gold maybe nothing.
During developing centers converted into black metallic silver, this conversion is
called reduction, this is the first thing will happen during film processing. The soft
tissue will become black, the centers in the bone also, amalgam that are no centers,later on the color of the silver will be converted to black with processing, you keep
processing your image will become darker.
Finally, when you put the film in fixer, unexposed crystals will be removed from
the film, we remove unexposed crystals because we dont want them to be affected
during the processing.
This is the reason why we have radiolucent images and radiopaque images
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Film processing steps
1. Developing
Purpose: is to reduce the exposed silver halide crystals chemically into black
metallic silver.
You can see partial development, complete and overdevelopment. If you
forget your film in the developer it will become darker.
The developer solution softens the film emulsion during this process
Main Factors:
Duration
Temperature of solution. Concentration of solution.
The temperature and concentration of solution may differ and this will
affect the duration of developing, so people increase temperature of solution
if they increase the concentration so the process will be faster, and this is how
we can increase the speed of developing.
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Usually we prefer 20 for developing for 5 minutes and 10 minutes in fixation.
Table 9-1
This table shows the components of the developing solutions;
note that quinine builds up Lactones, Elon builds up frictones.
Oxidation of solution will result in deterioration of the developing solution .
2. Rinsing
After development we have to rinse the film to remove the developer from the
film and to stop the development process. This step takes usually from 20 to 30seconds.
3.Fixation
After rinsing,
Purpose: is to remove the unexposed, unenergized silver halide crystals from
the film by using a chemical solution known as the Fixer, the fixer hardens the
film emulsion during this process.
Component of fixer solution: the main component of fixing solution ishypo-sodium thiosulfate.
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4.Washing
After fixation a water bath is used to wash the film for around 20 minutes. If
the temperature we follow during processing is 68 F (20 c)we wash the filmaround 20 min.
5.Drying
After washing, there are many ways for drying the film ;films may be air-
dried at room temperature in a dust-free area or placed in a heated drying
cabinet at temperature which is not exceed 120 F, or by using fans.
Film Processing Solutions forms
1. Powder, must be mixed with distilled water.
2. Ready to use liquid, no need to prepare it.
3. Liquid concentrate, must be mixed with distilled water.
Chemical solutions should be changed every 3 to 4 weeks depending on number
of films process but its usually takes around 1 month, solutions have become
depleted with time and use by physical removal and evaporation. Removing,
oxidation, evaporation, all of these will lead to depletion and we have to change or
to replenish the solutions. Replenishing is done daily by using highly concentrated
solutions, while changing is done monthly.
Homework: how often do we change the fixer solution? Does it depend on the
number of films processed?
The fixer may be affected by dilution because there is rinsing before fixation, so
replenishing by using few drops of super concentrated solution.
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So manual maybe consider as the old methods, we have visual and fixed time
temperature way.
This is the manual, we put our hands in the box, which prevent the light, and we
have usually developer, water, fixer and water.
Develop > 5 minutes at 68 degrees
Rinse > 30 seconds (agitate continuously)
Fix > 4 minutes (Agitate intermittently;
5 seconds every 30 seconds)
Wash > 10 minutes in clean running waterHang films to dry
.
Q: Is it necessary to work inside a darkroom?
No, its not. We have the day-light loader boxes, by
this there is no need to be inside the darkroom,
and otherwise it has to be inside the darkroom.
Look here at the picture, this window glass allowed
only the safelight to go to the films.
Processing Tank
A container divided into compartments tohold the developer solution, water bath and
fixer solution. We use processing tank for
manual processing, instead of using cups we use
the tank; its cheap.
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In this figure processing tank showing developing and fixing tank inserts in bath of
running water with overflow drain.
-The insert tank: two removable tanks filled with water, both are placed in themaster tank, the developer solution is placed in the insert tank on the left and the
fixer solution is placed in the insert tank on the right.
-The master tank: suspends both insert tanks and filled with water.
-The overflow pipe: used to control the level in the master tank.
The typical tank is made of stainless steel, the master and insert tanks must becleaned each time the solutions are changed, by using a commercial stainlesssteel tank cleaner or a solution of hydrochloric acid and water.
The temperature of the developer and fixer solution are controlled by the
temperature of the circulating water in the master tank.
Manual processing
Place hanger with films attached into the developer for 5 minutes. The lid isplaced over the tank if you plan to leave the darkroom during development.
The silver halide crystals on the film are converted to black metallic silver inthe developer. (after developing the film will convert from green color to black
or gray and image begins to form).
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After removing the lid, place the films in the rinse water and continuouslyagitate for 30 seconds. Next put the films in the fixer for 4 minutes and agitate
for 5 seconds every 30 seconds. (Purpose of agitation is to get rid of air
bubbles inside the solution, and to make an equal distribution of solution
around the film.)
Remove the films from the fixer and place in the water bath for 10 minutes(double the time of developing).
Remove film from the wash water and hang films to dry. (Washing for 20minutes while rinsing for 20 seconds).
Thermometer
Necessary for manual processing, we put it inside the developer to determine the
temperature of it.
Manually we have two methods:
1. Visual method, it means when you inspect your film after putting it in the
developer solutions, rinsing it and fix it. So its not a standard guide, it depends on
human factor and should be limited to cases where special density of the final image
are required. It depends on human eye.
2. Fixed time temperature method; so when we increase the temperature we
decrease the time, it depends on manufacturer chart. The chart is reliable and
standardized.
This is the daylight loader automatic processing which we are using in our clinic, as
you can see the component:
1. The processing housing2. The film feed slot
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3. The roller film transport4. The developer compart5. The fixer compartment6. The water compartment7. The drying chamber8. A replenisher pump and9. The film recovery slot.
Automatic p
-The film is transported dir
rinsing step.
-The major advantage of thi
minutes.
-we have a daylight loader
Homework: why there is no
-Automatic processing is o
reasons:
I. Less processing time is re
II. Time and temperatures a
r
ent
replenisher solutions
ocessing
ctly from the developer solution into
s process is the time saved, it require
lso.
rinse step?
ten preferred over manual processin
uired.
re automatically controlled.
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he fixer without a
only from 4-5
for the following
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III. Less equipment.
IV. Less space is required.
Also there are more standardized results, elimination of rinsing, higher temperatureof solutions and higher concentration of solutions .however, this will result in
deterioration of solutions, replenishing of solutions.
This advantage is more expensive, much regular maintenance, requires proceed
a minimal number of films per day, so there is a certain extent of the films we must
process them.
Higher temperatures will lead to deterioration and also lead to chemical foggy of
radiographs, foggy can be due to a high temperature of the developer solution.
-Foggy ( ), it has many causes: fig 9-31
1-Not safelight and light leaks in the darkroom.
2- Chemicals and radiation.
3- Outdated films.
-Solutions for any other automatic processes are different should not be used
interchangeably.
A homework question: Why cant we use manual processor solutions for
automatic processor?
DarkroomWe rarely see it nowadays because weve stopped processing and if we want to
process we do it under daylight loader .However, in the past we had darkrooms forprocessing the films.
Location of the darkroom
It must be near the area of x-ray unit, convenient, it must be large enough to
accommodate film processing equipment and to allow ample working space, the size
of the darkroom is determined by these factors:
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1. Volume of radiographs processes.
2. Number of people using the room.
3. The type of processing equipment, either processing tanks or automatic processor.
4. Space required for duplication of films and storage.
Also it must be light-tightno light leaks should be observed, When the door is
closed no white light should be seen.
-Light leaks: any white light that leaks into the darkroom.
We need 2 types of light in the room and it depends on whether you want to usethe light during processing, or if you want to clean the room itself. We shouldnt use
florescent light because it will affect the films.
Two types of lightings are essential in a darkroom:
1. Room lighting, if you want to clean the room you need overhead white light, also
we use it for mixing chemicals.
2. Safe lighting, if you want to process films inside the darkroom because its darkyou cant see anything, you need light to provide illumination in the dark room and
its called safelight.
-A safelight consists of a lamp equipped with a low-wattage bulb (71/2 or 15 watt)
and a safelight filter.
-A safelight filter removes the short wavelengths in the blue-green portion of the
visible light spectrum and at the same time it permits the passage of light in red-
orange range.
- We have two types of filters, GBX-2 filter and *38:05*
GBX-2 use for all films in 15 wattage
** for intra oral films only,
orange filter, 10 wattage bulb.
- if Films that are unwrapped too close to the safelight or exposed to it more than 2
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to 3 minutes appear fogged, so a safelight must be placed a minimum of 4 feet (1.2
m) away from the film.
-Extra oral films are more sensitive than intra oral films.
< fig 9-4>
Q: How to know that your safelight is safe?
Coin test!!
First of all you have to turn off the lights in the darkroom so unwrapped unexposed
film and place it on a flat surface at least 4 feet, the coin is on the top of the film,
leave it for 2-3 minutes this is to be sure that your safelight is safe.
And if your safelight is not safe, exposure will happen and all areas except the
area of the coin will be affected (become gray), it will become gray when you process
the film. If your safe light is safe all of the film will be clear.
Ventilation
If we need good ventilation we use air condition or electric fan, ideal temperature
is 70F, if the temperature is more than 30C it may cause fogged film.
Humidity
The humidity level should be maintained between 50% and 70%, if it becomes too
high, the film emulsion doesnt dry, when its too low static electricity becomes a
problem and causes film artifacts.
The darkroom work spaceIt must include an adequate counter area where films can be unwrapped before
processing. It also should be cleaned and dry.
The darkroom storage space
It must include ample room for chemical processing solutions, film cassettes and
other miscellaneous radiographic supplies.
Boxes of opened extra oral film must be stored in the darkroom. It should be light-
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tight.
Unopened boxes should not be stored in dark room.
Homework: why Unopened boxes should not be stored in dark room.
Other requirements
Film Hangers, drying operators,
Processing errors
We see errors while using manual processing but we may not see them in automatic
processing.
1- Undeveloped film2- Overdeveloped film, too much developing time3- Reticulation of emulsion, leads to sudden changes in temperature, for example
the developer is too hot and the fixer is too cold so this will lead toreticulation.
4- Developer spots, dark black spots.5- Fixer spots, white and usually large.6- Yellow-brown satins, caused due to insufficient fixation time, insufficient
rinsing and using of exhausted developer or fixer.
7- Developer cutoff.8- Fixer cutoff.9- Overlapped films, if you put two films inside automatic processor for example
without waiting for 15-20 sec. it are a common mistake done by students.
10- Air bubbles.11- Fingernail artifact, this is seen when the film emulsion is damaged by the
operators fingernails during rough handling of the films and it will lead to
ionize the silver atoms .and its a common mistake.
12- Fingerprint artifact.
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13- Static electricit14- Scratched film,15- Light leak, hap
depends on the area
16- Fogged leak, itdarkroom, outdated
if the developer solut
homework: whats t
films?
y.
if you handle the film roughly you wil
ened due to accidently exposure of fi
which is exposed to the light.
results from: improper safelighting, li
ilms, improper film storage, contamin
ion is too hot.
e difference between air bubbles an
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l scratch the film.
lm to the light. It
ht leaks in
ated solutions and
water droplets in
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Note: To get more details a
you can find them in these
Best wishes to all of you
Sawsan Jwaied thanks for t
done by: Eman Idkaidek.
Corrected by Saw
bout problems and errors of processi
igures: 9-4 , 9-5 , 9-6 , 9-7 pages 11
and sorry for any mistake.
e help