DARK ROOM PROCEDURES

Presenter – Dr. AnurajModerator – Dr. C.N. Pradeep Kumar

WHAT IS A DARKROOM ?

Enclosed area or chamber dimly lit by safelight (usually red) but otherwise intentionally lightproof room where films are handled and processed.

DARK ROOM LAYOUT

A room should be set aside as a permanent dark room, ideally with a floor area of not less than 10sq. m.

The room must be capable of being made completely lightproof. It should not be damp or subjected to extremes of temperature. Water and electrical outlets should be provided. Sufficient space to accommodate a dry bench , a wet bench and a

sink. Too large room is as undesirable as small room. Should be near the x-ray examination area. Should be well ventilated. The wall should be constructed of solid concrete (15 cm thick), have

a lead box inside to store boxes of unexposed films currently in use. The walls and roof should be painted by white or cream enamel as

such a paint acts as a good reflecting surface for safe light. X-ray rotating warning light in hallway switched "on" signaling that x-

ray machine is operating.

LOCATION Centrally located Serviced by hatches

from the adjacent imaging room

Away from damp or hot areas

Accessible in terms of power and water supply

Adjoining viewing room

SIZE

Minimum floor area of 10 sq meter

Ceiling height of 2.5 - 3 meter

Size may be reduced depending upon the department needs

LIGHT PROOF

The first requisite of a processing room is the exclusion of all external white light when radiographs are processed.

Photosensitive crystals in film emulsions are extremely sensitive to visible light, and any light leaking around a door or window may fog and ruin the films.

A door that can be locked to avoid accidental exposure of film to white light.

Alternatively a light outside the door indicating that the darkroom is in use. When the white light in the darkroom is switched off, the indicating light outside automatically goes on

RADIATION PROTECTION Walls adjacent to the radiographic

room should be shielded with correct thickness of the lead all the way to the ceiling

In the interests of both darkroom staff and film material alike

1.6 mm lead is mostly used

FLOORS

Non-porous flooring Non-slip flooring Chemical resistant Stain proof Durable & easy to

maintain Light coloured (low-

light working conditions)

Asphalt tiles Porcelain tiles Clay tiles Plastic tiles may be

used in the dry dark-rooms

WALLS/CEILING

Light in colour to reflect as much light as possible onto the working surface

Easy to wipe or clean Covered with chemical resistant

materials Special paints, varnish, ceramic or

plastic wall

VENTILATION AND HEATING Satisfactory working conditions for the staff Good film handling and storage conditions Efficient automatic processor performance Relative humidity is maintained at around 40-60 % Room temperature maintained between 18-20 degree

celsius A minimum of 10 air changes per hour All of these conditions can be achieved by using a

good air-conditioning system Alternatively, fairly satisfactory ventilation can be

achieved by using an extractor fan sited higher than and diagonally opposite a second fan, the latter being so placed as to obtain fresh and filtered air from outside.

TYPE OF ENTRANCE

SINGLE DOOR SYSTEM

DOUBLE DOOR SYSTEM

MAZE TYPE ENTRANCE

LABYRINTH

ROTATING DOOR SYSTEM

DARK ROOM ENTRANCE

REVOLVING DOOR SINGLE DOOR

DOUBLE DOOR MAZE

MAZE TYPE ENTRANCE

ROTATING DOOR ENTRANCE

DARK ROOM ILLUMINATION

WHITE LIGHTING

SAFELIGHTING

WHITE LIGHTING For inspection & maintenance of

cassettes & screens Cleaning of work surfaces Servicing of equipment

Sited close to the ceiling Moderate in intensity

(60w tungsten, 30w fluorescent ) Preferably centrally placed

SAFE LIGHTING

DIRECT SAFE LIGHTING:

Light from safe lamp directly falls onto the work surface Eg. Beehive safelamp

Minimum distance of 1.2 m/ 4 feet from the working surface

Best for loading & unloading areas

INDIRECT SAFE LIGHTING

Directs the light towards the ceiling which reflects light back into the room

Is intended to provide general illumination of the dark room

Suspended atleast 2.1 m above floor level

SAFE LIGHT FILTERS Sheet of gelatin dyed to

the appropriate colour and sandwiched between two sheets of glass for protection

Used in conjunction with a 15 W lamp

Extremes of heat and temperature deteriorates the filter gelatin

Should be cleaned periodically

How Does A Safelight Work? When white light is passed

through coloured filters, certain wavelengths (or colours) are absorbed by the filters, whilst those wavelengths, which correspond to the colour of the filters will be transmitted.

Making the correct selection of safelight filter (matching the filter to the film), means choosing a filter, which will transmit a colour to which the film is relatively unresponsive, whilst stopping all light to which the film is most sensitive.

WHICH COLOUR FILTER TO USE? X-ray films have the highest sensitivity

to the blue-green part of the light spectrum . The X-ray film is less sensitive to light in the opposite region of the spectrum - i.e. the yellow and red region. It is obvious that the blue filter cannot be used, neither a green color filter as it is so close to the blue. Therefore safelights are safest when made with amber or red filters.

How Safe Is Safe Lighting?

No safe lighting is completely safe; all films will become significantly fogged if exposed to safelights for long enough.

This is because safelight filters are not perfect absorbers of the undesirable wavelengths and, in truth, all films have some sensitivity to all wavelengths.

Thus, the intensity of illumination and the film-handling time must be kept to a minimum if significant fogging is not to occur.

Safelight illumination test Place a coin on a small piece of photo paper.

Let it sit for 20 min. and develop the paper. If you see the outline of the coin, your safelight isn't safe

If the safelight is not safe, you should do one of the following to correct the problem:

1. Replace the bulb with one of lower wattage 2. Raise the safelight lamp higher from

working surface 3. Check the filter - may be cracked or broken

DARK ROOM EQUIPMENTS

Automatic processor Manual process unit Processing chemicals Hangers for suspending film Cassette Film storage hopper Loading bench Cupboards

DARK ROOM EQUIPMENTS

Film cassettes: A cassette is designed to hold the x-ray film and intensifying screens in close

contact. The front face which is of aluminum or plastic, faces the tube while the other

side have a sheet of lead to absorbed back-scatter screens and cassettes are of course made in various sizes to correspond with standard film sizes.

Mounting intensifying screens in the cassette Intensifying screens should be never be loose but must be properly mounted

into the cassette. Because certain adhesives interact with the screens it is advisable to use

only the double-sided tape provided by the manufacturers.The care of cassettes Do not drop them on a hard floor Do not trap the edges of the screens when the cassette is closed Cassettes should be kept clean and there is always the danger of blood or

urine leaking to the inside of the cassette. When a cassette must be placed in a dirty situation put it in a plastic bag.

Dry Bench The dry bench is where the cassettes are unloaded and

recharged with fresh film. It must be impossible for splashes of developer to reach the dry bench surface.

The top of the dry bench must be large enough to accommodate the largest cassette in use when opened out.

The top surface should be either of wood or linoleum. Plastic laminates are not recommended because they hold static charges of electricity which can cause marks on films.

It is usual to store film boxes, especially those in current use , beneath the dry bench , either in a cupboard ( protected if near an X-ray set ) or in a film hopper.

Wet Bench The wet bench is where the processing of the films is carried

out. The usual method is to use a set of  tanks holding

developer ,rinse water and fixer , and a larger tank for washing the films.

DARK ROOM DRY BENCH SYSTEM

PROCESSING TANKS 1. MASTER TANK This tank serves as a water jacket to hold

the insert tanks and is usually large enough to provide space between insert tanks for rinsing and washing of films. The water assists in maintaining the same / constant temperature in the insert tanks.

2. INSERT TANKS These are removable containers for the

individual processing solutions - (developer and fixer), and are spaced in the master tank

MANUAL PROCESS UNIT IN PK TB HOSPITAL

AN AUTOMATIC PROCESSOR

AUTOMATIC PROCESSOR

PROCESSING CHEMICALS

                                       

Hangers used for suspending films during processing

CASSETTES

FILM BIN

FILMS

8 X 10

10 X 12

11 X 14

14 X 17

TYPICAL DARK ROOM FILM BINSLOTS OF DIFFERENT

SIZES

14 X 17 11 X 14 10 X 12 8 X 10 7 X 17 6 X 12 14 X 36

35 X 43 28 X 35 25 X 30 20 X 25 18 X 43 15 X 30 35 X 91

RADIOGRAPHIC FILM SIZES

Film Processing

RADIOGRAPHIC FILM

Gurney Mott hypothesis

This process repeats.

Chemical sensitization

Chemical sensitization of the crystals are produced by adding allylthiourea, a sulfur containing compound to the emulsion , which reacts with silver halide to form silver sulfide.

Sensitivity Speck• This Silver

Sulphide is usually located on surface of the crystals and is referred as “sensitivity speck”.

Point defect in cubic lattice.

Sensitivity speck by Silver sulfide

The sensitivity speck traps electron and form latent image.

The film is then passes through the following four steps

Developing

Fixing

Washing

Drying

Developing Agent

AcceleratorRestrainersPreservative

HardenerSolvent

CONSTITUENTS OF DEVELOPINGSOLUTION

Development

It is the first stage in processing of the radiograph.

Amplifies latent image by 100,000,000!

The primary purpose: convert the invisible latent image into visible form.

Processing initiated at latent image speck

These are the reducing agents, which carry out the primary function of supplying the electrons that convert the exposed silver halide grains to silver.

Characteristics:1. Selectivity2. High activity3. Should be resistant to bromide ions in the

solution.

Developing Agents

1.DEVELOPING AGENTS

Hydroquinone + phenidone/metol

Hydoquinone(developer) +silver ions quinone(oxidised develper) + silver atoms + hydrogen ions

Phenidone(developer)+silver ions oxidised developer+silver atoms+hydrogen atoms

Advantages of PQ developers1. Tolerant of increase in bromine ion concentration.2. High selectivity and low chemical fog.3. Adequate activity even in low concentrations.4. Available in liquid concentrate form.5. Fast acting6. Adequate contrast7. Super additive effect

SUPER ADDITIVE EFFECT

ACCELERATOR/ACTIVATOR/BUFFERING AGENT

Alkaline medium for the action of PQ-accelerates the developing process

KCO3 or KOH Ideal range of pH: 9.8-11.4

RESTRAINER/Anti-foggant It reduces converting unexposed AgX to Ag and thus prevent chemical fogging.

KBr, benzotriazole(used with PQ developer)

DEVELOPING SOLUTION

PRESERVATIVE

It reduces the oxidation of developing agents.

Eg: Potassium sulphite

HARDENER It controls gelatin swelling to minimize risk of physical damage.

Eg:Glutaraldehyde

DEVELOPING SOLUTION

SEQUESTERING AGENT Prevents the precipitation of insoluble

mineral salts which occur in hard water areas

EDTA containing compounds are usedSOLVENT Carrying medium for dissolving the

developer constituents Softens the film emulsion gelatinMC used : Tap water

DEVELOPING SOLUTION

Temperature of the developing solution Total time of the development

An adequate combination of both is important for complete development

FACTORS AFFECTING DEVELOPMENT

Optimum temperature is 20-22oC Below 16oC, action of hydroquinone ceases

Radiograph lacks contrast and density Can be compensated by increasing the developing time.

Above 24oC (too warm) emulsion softens. Chemical fog results

TEMPERATURE FOR DEVELOPMENT

During development not all the silver halides are reduced. Only 40% get reduced

The remaining silver halides greatly impairs the

usefulness and permanence of the developed

radiograph and hence have to be removed.

STAGE 2:FIXING

It has four major functions Stop any further development

Makes the solution more acidic Remove the unexposed AgX from the emulsion

Convert it to soluble compounds and remove it Makes the image chemically stable and no longer photosensitive

Completes the process of hardening of emulsion

Minimizes water absorption and reduces drying time

FIXATION

1. Solvent2. Fixing agent3. Acid4. Hardener5. Buffer6. Preservative7. Anti-sludging agent

 

Constituents of the fixing solution:

1.SOLVENTWater

2. FIXING AGENT2 agents:

Cyanides Poisonous Not generally used.

Thiosulfates - Sodium and Ammonium Salt (more active) – called Hypo.

AgBr + sod. Thiosulfate

Ag thiosulfate complex + NaBr(water soluble)

3. Acid: Prevents dichoric fog by inhibiting developing

agents. Provides a suitable environment for the

hardening agents in the fixer. Acetic acid is used usually at a pH of 4-4.5.

4. Hardener: Reduces drying time and prevents physical

damage. Aluminium chloride and aluminium sulfate (or

Chromium compounds) are used commonly. 5. Buffer:

Prevents sulphurization. Neutralizes the developer Sodium acetate is commonly used in conjunction

with acetic acid

6. Preservative: Retards decomposition of thiosulphates Sodium sulphate is commonly used

7. Antisludging agent: Boric acid is commonly used and this prevents

sludging of insoluble aluminium compounds in the hardener.

Purpose of washing is to remove fixing solution from the surface of the film.

If the film is not properly washed, it will show a brown staining caused by thiosulfate (fixing agent that remains in the emulsions).

The process by which washing works is diffusion.

Tap Water is mainly used

STAGE 3 : WASHING

The drying medium is dry air of low humidity, which accelerates the evaporation process and reduces drying time.

Film drying box Heating element with a circulating fan. It can dry in 15 minutes. Film will dry properly if hung in air for a longer period (1+ hours).

STAGE 4 : DRYING

The longer the film spends in the fixer, the longer the wash time needed

This is a 1:2:3 ratio of developer to fixer to wash

TYPES OF FILM PROCESSINGAUTOMATIC MANUAL

• Unloading the film• Inserting into processor

Unloading the filmLoading the film onto a hanger DevelopmentFixingWashingDrying

AUTOMATIC PROCESSOR

Tanks 1. For Developer solution2. Fixer solution3. Wash tank for water

During a 90s processing cycle Developer------ 26s Fixer ----- 15s Wash ----- 15s Drier ------ 24s Travel time----- 10s

MANUAL PROCESSING

MANUAL PROCESSING

DEVELOPINGIt is done by time – temperature techniqueHere film is immersed in developer for 4 minutesTemperature is maintained at 20 CAt intervals with in 4 minutes film is examined under safelightsIf image seems to lack expected density at 4 minutes, development is continued

MANUAL PROCESSING

RINSING Purpose is to slow the action of developer and to remove it from the surfaces of the film, done by a plain rinse bath.

To stop the action of developer, done by acid stop bath.

FIXING After rinsing, the film is immersed in fixer solution

Fixing time can be up to 5 minutes

MANUAL PROCESSING

WASHING Immerse the film in large tank or in a series of tanks through which water is kept flowing.

Time duration:- 20 – 30 minutes DRYING Hot air drying cupboards or by rapid drier machines.

Temperature may vary from 40-50 C

Developing – formation of the image

Fixing – stopping of development, permanent fixing of image on film

Washing – removal of residual fixer

Drying – warm air blowing over film

4 Steps of Processing

COMPARISON

• DEVELOPING TEMP 200 c

• FIXING TEMP 200 C

• WASHING TEMP 200 C

• DRYING TEMP 430 C

• DEVELOPING TIME 3-5 MIN

• FIXING TIME 2-10MIN

• WASHING TIME 15-30MIN

• DRYING TIME 15-20MIN

AUTOMATIC

• 350 C

• 350 C

• 350 C

• 570 C

• 25s

• 15s

• 15s

• 20s

MANUAL

CLEANING THE PROCESSING TANKS The action between the mineral salts

in the water and carbonate in the developing solutions produces a deposit on the inside wall of the processing tanks.

A commercially prepared stainless steel tank cleaner can be used to remove these deposits.

Or simply brush thoroughly with a brush and water.

The developing solution should be tightly covered when not in use to reduce oxidation.

The solution should be discarded and replaced after three months of use because oxidation and accumulation of gelatin sludge and other impurities will cause poor development.

As the solution weakens it first turns yellow, then brown. When it turns brown, indicating exhaustion, it should be replaced.

Few important points to be kept in mind

Christensen’s physics of diagnostic radiology

REFERENCES

Thank You!!!