DARK ROOM.ppt

DARK ROOM
Dr. Abhilash Jayaram

DARKROOM
CONSTRUCTION/DESIGN
Location of Darkroom:-
 Darkroom should be in close proximity to
where the work of radiographer is carried out.
 Centrally sited and serviced by hatches from
adjacent imaging rooms.

DARKROOM
CONSTRUCTION/DESIGN
Location of Darkroom:-
 Sited away from damp or hot areas.
 Accessible in terms of power and water supply.
 Adjoining viewing area where processed films
are checked and sorted.

Plan view of a three-room department
serviced by one darkroom

Plan view of a four-room department serviced
by one darkroom

DARKROOM
CONSTRUCTION
Certain structural characters are important:-
 Nature of floor
 Walls and ceiling
 Ventilation and heating
 Type of entrance.

Floor, walls and ceiling
Important considerations:-
 Number of people likely to work in a particular
darkroom.
 Number of examinations made in the
department.
 Type of processing.

Floor, walls and ceiling (cont.)
 Requires a minimum floor area of 10 m2.
 Ceiling height should be around 2.7- 3m. (But
not greater than 3.3 m if ceiling reflector lamps
are to be used).

Nature of floor material:-
1. Non-porous.
2. Resistant to staining by chemicals.
3. Does not become slippery when wet.

 Semi-vitreous and non- vitreous tiles are
sensitive to stains.
 Concrete or ceramic tiles become slippery
when wet.
 Improved by inclusion of small amount of
abrasive, granular material.
 Satisfactory resistant substances are those of a
composition which has a high proposition of
asphalt: porcelain.

 Same recommendations apply to walls as to
the floor, particularly in neighborhood of sinks
and wet processing equipment.
 Protected to a height of at least 1.3m.
 Ceramic or plastic tiles can be applied to wall
surfaces.

 Good quality paint should give adequate
protection.
 Untreated brick work are likely undergo a
gradual process of destruction.
 A glossy cream or white paint on the wall do
well.
 Orange or green, are to be avoided as they
reflect light from safelight poorly.

 Paints to be acid-resistant.
 Paint should not produce flakes which are
likely to fall on sensitive materials.
 Plaster is to be avoided.
 Modern emulsion paint satisfactory.

 Modern practice is to obtain as much reflected light
as possible which provides diffuse illumination.
 Diffuse illumination will improve working condition.
 Reflected light does not differ in wavelength from the
incident light and offers no greater risk to sensitive
materials.

Radiation protection
 Require protection from ionizing radiations-
especially X-rays from adjoining radiographic
room.
 Primary beam is never directed at the wall of
darkroom.
 Ceilings and floors also should be considered.
 These remarks also apply to storerooms where
reserve stocks of film may be kept.

Radiation protection (cont.)
 Room in which film is stored or handled should have
a lead equivalency of 2mm.

Appropriate materials for this purpose are:-
 1. A 25 mm layer of high quality barium
plaster (1 part fine BaSO4; 1 part coarse
BaSO4; 1 part Portland cement.)
 2. A single brick wall; 225mm solid brick.
 3. A wall which is half in thickness + half-inch
layer of high quality barium plaster.

 4. A 150mm thickness concrete.
 5. Lead ‘plymax’ board with 2mm of lead.
 Particular attention should be given to
obtaining an overlap at points of discontinuity
in the walls.

 Entry of ionizing radiation can be proved by
placing a coin on an envelope-wrapped film.
 The coin should lie between the film and the
surface of wall.
 It is left for some time, for a week perhaps.
 If the room is not adequately protected, a faint
image of the coin will be apparent on the test
film.

Ventilation & Heating
 When ventilation is poor even the performance
of automatic processor will be effected.
 Humidity is raised, that leads to inefficient
heat loss from the processor.
 Films may show increased density and
fogging.
 An increase in humidity cause inadequate film
drying.

Ventilation & Heating
 Space recommended for a technician in a darkroom is
1,000 cu.ft.
 It is sometimes recommended to have windows for
darkroom.
 Air in the darkroom should be completely changed at
least 5-10 times/ hour.

Ventilation & Heating (cont.)
 Done by cross ventilation by means of an
extractor fans situated at a high level, while air
is drawn in from outside source at a low level.
 Air intake should be from outside and ideally
would be filtered to remove dust.
 Apparatus for intake of air may be blow-in fan.

 Must be light-trapped.
 Ideally intake and extraction would be from
diagonally opposite points.
 An intake fan will lose efficiency if the
temperature of the room is much greater than
outside.
 This will be improved if incoming air can be
warmed by passing it through a radiator.

 Extractor fan should be given greater power
than their intake companions.
 Darkroom temperatures should be maintained
between 65°- 68° F (18°-20°C).
 Relative humidity of atmosphere ideally
should be 40 to 60%.
 A good air-conditioning system would be more
efficient.

Types of Entrance
 Single door,
 Double doors,
 Labyrinth,
 Rotating door system.

Single Door System
 Access is via a single door
 Ensure door is capable of totally excluding the
light.
 Customary to link electronically the door
locking mechanism with lighting ciruit.
 Relatively inexpensive.

Double Door System
 Each door should be sturdy in structure and
well fitting.
 Employment of double doors arranged on
either side of a small vestibule.
 The dimensions of vestibule may be no larger
than is required to accept one adult of average
build.
Some variations in double door:-
 Inner door to be sliding type.

Plan view of a darkroom with double door
light lock entrance

Labyrinth
 Consists of 2 parallel passages and a facing
wall.
 Design of labyrinth should be such that light is
absorbed at least three times between external
area and darkroom.
 Aim is to diminish the intensity of light to a
harmless level.

Labyrinth
Labyrinth’s effectiveness will be greater if:-
 A matt black paint is used for interior of
passages.
 Vertical height of the entrance is limited to 2
meters.
 Length of each passage is not less than 3
meters.
 Width of each passage is not more than
700mm.

Labyrinth
Advantages of Labyrinth are:-
 Provides easy and instant access to dark room
at all times.
 Offers no hazard to a single-handed operator.
 May effectively participate in the ventilation
 Adaptable.

Fire Safety
 All dark rooms should be provided with an
alternative exit and left unobstructed all the time.

Dark room Illumination
 Electric shock is a potential hazard.
 All lights in the darkroom should be operated
by a pull cord switch.
 Electric points should be of three-pin shuttered
type and waterproof.
 Should be properly earthed.

Dark room Illumination (cont.)
Two categories:-
 General white light
 Safe light
 Viewing equipment.

General white light
White light is necessary for following tasks:-
 Inspection and maintenance of cassettes and
screens.
 Cleaning work surfaces and floor.
 Servicing the equipment.

White Light
White light should be:-
 It should placed close to the ceiling to avoid
strong shadows.
 Moderate in intensity (e.g. 60 W) in order to
make visual accommodation under safelight
easier.
 Tungsten rather than fluorescent.

Safe lighting
 Should be less than the maximum level of
brightness permitted by most sensitive material
which is being handled by it.
 The term “safe” implies only a degree of
safety.
 All films become fogged if exposed to
safelight for long enough.

How does a safelight work?
 When light is passed through coloured filters,
certain wavelengths are absorbed by filters.
 Those wavelengths which correspond to the
colour of filters are transmitted.
 Choosing a filter which transmits a colour to
which the film is relatively unresponsive.

Safe lighting (cont.)
Sensitivity is related to:-
 Wavelength or colour of light.
 Intensity of light and
 Duration of exposure.

Attention to be paid to:-
 Correct colour of safelight chosen.
 Wattage of lamp used.
 Their distance from any point at which
sensitive material is handled.

 Red or brown lighting is generally employed.
 They represent the region of spectrum for
which we have greatest visual sensitivity at
low levels of illumination.
 Lacquered bulbs or colored glasses are not
satisfactory.
 These are likely suffer cracks in their coating.
 They also does not provide a sufficient range
of colour to be useful.

 An ordinary pearl bulb of not more than 25
watts is used.
 Safelight should be sited a minimum of 1.2 m
from the film.
 A coloured filter is placed in front of the bulb
which will tint the light of required hue.

Safelight filters
 Are sheet of gelatin dyed to appropriate colour and
sandwiched between two sheets of glass.
 Gelatin will deteriorate in extremes of heat and
moisture.
 Most common cause of overheating of gelatin is use
of an electric bulb of too high wattage.
 Safe illumination appears to have diminished in a
darkroom because cleaning might be overdue.
 Safelight and filters require regular attention.

 Safelighting can be either direct or indirect.

Direct safelighting
 Lamp has a circular filter 14 cm (5.5
inches) in diameter.
 Suspended from the ceiling or fixed to
the wall.
 Placed such a way that sensitive material
is normally handled no nearer to it than
122 cm (4 feet).

Direct safelighting (cont.)
 Films should not be held close to the
safelamps.
 Direct safelighting is ideal for film
loading and unloading areas.
 Often situated near to a manual
processing unit; lamp is needed for the
inspection of the film during
development.

Direct safelighting (cont.)
 Often situated above the feed tray of a
automatic processor.
 Lamp illumines the work area during the
introduction of a film, light goes out as soon as
the processor has accepted the film.
 Reappearance of light indicates processor’s
readiness for next film.

Indirect safelighting
 Intended to provide general illumination of the
darkroom.
 Safelamp directs the light towards the ceiling
which reflects it back into the room.
 Standardization of reflective abilities of the
ceiling is needed.
 It should not have a dull surface.
 Should be painted a glossy pale cream or
white.

Indirect safelighting
 The height of the ceiling should be within 2.7-3.3
meters.
 If high ceiling cannot be avoided, reflectors are
hanged 1 m above the safelamp.
 Some safelamp has filters on both surfaces suitable
for providing both indirect and direct illumination
simultaneously.
 Allowed for every 6.5 m2 of floor space.
 Lower edge of lamp should be 2.1 m above floor
level.

Safelamp for both direct and indirect
illumination

Safe film-handling time
 Maximum time for which a film can be exposed to the
safelights without any appreciable degree of fogging.

Safelight Test
 Tests to ascertain that illumination employed is
safe.
Required in following circumstances:-
 Darkroom is a new one.
 Safelights have been changed or additions
made to them.
 Particular lamp is suspect as the cause of
fogging.

Safelight Test (cont.)
 A cardboard holder to take the film to be tested
should be previously prepared.
 The holder should be of enough size to accommodate
the film.
 The film selected for the test should be of the fastest
speed.
 The selected film is taken in a cassette to an X-ray
room.
 A sheet of lead is used to cover half of the cassette
lengthwise.

Safelight Tests (cont.)
 Other half of the film is given a slight
exposure to X-rays sufficient to produce on
development a density of 0 ּ8.
 In the darkroom all lights are switched off.
 Exposed films are more sensitive to light than
films which have had no exposure.
 The holder is then completely covered by a
large piece of card.

 The holder with the film is placed on the loading
bench, the film being uppermost and towards
safelamp to be tested.
 Switch on the safelamp(s) to be tested.
 The card is withdrawn to expose a strip at the upper
edge of the film for 4 minutes.
 The card is withdrawn to expose another strip of film
for 2minutes.
 Film again completely covered with the piece of
cardboard.

 Film is processed in darkness.
 Film can be divided vertically into 4 regions.
 Area A has neither been pre-exposed nor
received safelight exposure.
 Any density in this area is basic fog.

 Area B has had no X-ray exposure, has
received a controlled series of increasing
exposure to safelighting; this is the reaction of
unexposed film.
 Area C has been pre-exposed to X-ray and
received safelight exposure.
 Area D has pre-exposed to X-ray but received
no safelight.

 Strip 6 10 seconds
 Strip5 10+15= 25 sec
 Strip4 10+15+30= 55 sec
 Strip3 10+15+30+60=115 sec (1.9min)
 Strip2 10+15+30+60+120= 235 sec (3.9min)
 Strip1 10+15+30+60+120+240= 475 (7.9 min)

 The area is examined with densitometer.
 Area D – To establish pre-exposure to X ray
was 0.8.
 Area A – Used for measurement of basic fog.
 Area B – examined for the first density which
is 0.05 above the basic fog.
 As soon as such a density is found, look at the
edge of flap and calculate total time of
exposure.

 This time represents maximum safe film-
handling time for unexposed film.
 Similar way maximum safe film-handling for
exposed film calculated.
 Safe film-handling time for exposed materials
will always be shorter than unexposed film.
 If no such density appears, then safe for up to
8 minutes for exposed and non-exposed film.

 The first appearance of a density increase
which is more than 0.05 above the basic fog
indicates first unsafe period.
 The intensity of safelighting reaching the work
area must be reduced to give a longer safe
period of exposure.

 Typical safe film-handling time averages
between 20 – 45 S.

Viewing Equipment
 Provision is needed for assessment of wet
radiograph.
 Minimum requirement is a single illuminator
wall mounted above the processing unit,
attached directly to wall.
 Very susceptible to splashing, should be
protected from rust and corrosion.
 Illuminator should be operated by s pull-cord
switch.

Switching of light circuits
 White-light switching arranged to reduce the
possibility of it being switched on accidentally.
 Light circuits are controlled separately in a
‘dry’ area of room.
 Switches should be placed at a very different
heights.
 The switch for white-light put out of normal
reach.

Switching of light circuits (cont.)
 Safelight switch might be 1.5 m from floor and
the white-light switch 2 m from floor.
 Recommended to have a cord-operated master
control near the door of darkroom.

Switching of light circuits (cont.)
 Recommended to have a cord-operated
change-over switch which give either white or
safelight.
 Fitting an indicating lamp, outside the
darkroom door, wired in parallel with
safelights and provides warning when they are
in use.

Darkroom Equipment and Layout
 Overlap between wet and dry operations
should be avoided.
Well planned darkroom has following characteristics:-
 Effective separation of wet and dry operations.
 Orderly sequence of successive stages of work.
 Neat layout of equipment.
 Clear ‘traffic lanes’.

Darkroom Equipment and Layout
Equipments necessary to an X-ray darkroom:-
 A bench upon which to unload, reload
cassettes.
 Apparatus in which processing is performed.
 Essential accessories.
 Method of processing may be manual or
automatic.

The Darkroom with Automatic
processing
The loading bench:-
 Should provide enough space.
 Long enough to allow 3 or 4 of largest
cassettes to be placed open.
 Recommended allowance in length is 2.5 m/
operator, minimum width 600 mm.
 Height should be not less than 900 mm.

The loading bench
 Top of bench should be hard wood or teak.
 Thick linoleum is a good choice.
 Hard wearing, sound deadening and anti-static.
 Will not acquire static electric charge.

Automatic processors
 Only feed tray is of processor is kept in the
darkroom.
 The processed film may be collected and
viewed in the viewing area.

A through-the-wall position for
automatic processor

Film Storage
 For unexposed films immediate to use.
 Stock of unexposed materials for near future.
Film Hopper:-
 Films intended for immediate use are kept in hopper
under loading bench.
 Device is a cone shaped drawer hinged at its lower
edge.

Film hopper (cont.)
 Inside should be painted black.
 Has 4-5 compartments.
 Provide orderly storage of films with ready
access.

Film hopper (cont.)
 Each box of film should be opened.
 The contents should be unpacked and replaced
in the box so that folded edge of such covering
is uppermost.
 The box itself is then put into the hopper, both
as protection to the film and it prevents films
curving under their own weight.

Film hopper (cont.)
 Hopper must be well made and completely light-tight.
 Prominent printed warning should be outside that it
should not be opened in white light.
 A lock enable the hopper to be left secure.
 A drawer or door operated switch in series with white
lights, which can be fitted to hopper.

Film Storage (cont.)
Drawers:-
 Shallow light-tight drawers should be used.
 Drawers should be labelled.
 Less convenient.

Film Storage (cont.)
Cupboards:-
 Intended to stock a small current supply of
films for replenishment.
 Their dimensions should allow the boxes to
stand upright.
 Vertical divisions prevent tipping sideways as
the stock becomes diminished.

Cassette Rack
 It is a rack which may house loaded cassettes.
 Consists of number of vertical compartments
of various heights.

Cassette Hatches
 Allow cassettes and film to be passed between
radiographic room and processing room.
 Hatches should open on to the loading bench.
 Most conveniently fitted on a communicating
wall when X-ray and darkroom are adjacent.
 They enable the work to flow easily.

Cassette Hatches
Special features:-
 Light proof in structure.
 Interlocking device which prevent both doors
of hatch being simultaneously opened.
 Must be proof against X-rays, ensured by
incorporating lead.
 Some may be metal in construction others
made of plywood.

Cassette Hatches (cont.)
 Distinguishing between exposed films and
reloaded cassettes required.
 There are 2 compartments; one being labeled
‘exposed’ and other ‘unexposed’.
 Another pattern is lower horizontal
compartment for exposed materials, two
vertical sections for outgoing cassettes.

The Darkroom with a Manually
operated processor
Darkroom requires additional equipments:-
 Storage space for processing-hangers.
 Hot and cold water supply and sink.
 Storage space for packs of chemicals and
mixing equipments.
 Drying cabinet.

Hanger Storage
 Provided by wall brackets above the loading
bench.
 Only one type of hanger occupies any
particular bracket.
 Typical metal bracket projects about 230 mm
from the wall, holds about 12 hangers.
 End of brackets upturned to lessen the risk of
hangers falling.

Hanger Storage (cont.)
 A suitable height of brackets above the bench
would be 750 mm.
 The space between 2 brackets should be at
least 360 mms.

Darkroom Sink
 ‘Wet’ darkroom requires a general purpose
sink.
 Important not to place the sink in a position
continuous with loading bench.
 It should be along opposite walls of darkroom.
 Dimensions are 750 X 450 X 250 mms.
 Top of sink should not be less than 750 mm
from floor.

Darkroom Sink (cont.)
 Hot and cold water should be supplied.
 The taps should be placed 400 mms apart.
 Anti-splash device recommended.
 Draining boards are useful.
 Cupboards should be provided under or near to
sink.
 They are needed for the storage of equipments
for cleaning.

Drier
 Used for drying processed radiographs
 Most of the driers work with - hot air.
 Moist air exhausts from these driers.
 If the unit is situated in the darkroom, a duct
must be provided for air’s removal.
 Films are hung in the hangers, from the slotted
racks.
 A drip tray is often provided beneath.

Drier
 Cabinet has a fan for circulating the air and
heater elements to warm it.
 Doors should not be kept open when the heater
is on.
 Some units are provided with thermo-switch.
 Materials used in the construction of drier are
stainless steel and chemically resistant
substances such as PVC.

Viewing area
Should be furnished with:-
 Work surfaces,
 Compartment and shelving for film and patient
categories,
 Cassette storage racks,
 Viewing boxes and lobbies.

DARK ROOM.ppt

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