Lec7 Film Processing

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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

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