Darkroom Equipments and Processing PDF

8/24/24 DARKROOM 1. MANUAL EQUIPMENTS PROCESSING...

8/24/24 DARKROOM 1. MANUAL EQUIPMENTS PROCESSING PROCESSING APPARATUS 2.AUTOMATIC PROCESSING 2 3 With automatic With manual processing processing unit FILM HOPPER FOR THE STORAGE OF Automatic processor Manual processing Tanks UNEXPOSED FILMS Loading bench Loading bench For film storage – For film storage – hopper/drawers hopper/drawers Cassette racks Cassette racks Cassette hatches Cassette hatches Processing chemicals Darkroom sink Hangers for suspending film Processing chemicals + storage place 4 5 1  8/24/24 Film hopper/Film Bin Stores the unexposed films intended for immediate use Under the loading bench Inside is painted black Prominent WARNING should be written on outside that it should not be opened in white light 6 7 Hanger storage Stored on metal wall brackets Can hold max 12 hangers Two brackets should be placed 100 mm apart from each other Height of about 750 mm from the workbench 8 9 2  8/24/24 CASSETTE HATCH / PASS BOX CASSETTE RACK 10 11 FILM CASSETTE There are 3 key parts in radiography: A cassette is designed to hold the x-ray film and Film to record the intensifying screens in close contact. image Intensifying screen The front face - which is aluminum or carbon fiber, to expose the film faces the tube while the other side (back side) have a Cassette is to protect sheet of lead the screens and film Cassettes are made in various sizes to correspond with the standard film sizes 12 13 3  8/24/24 FILM CASSETTE A cassette holds two intensifying screens one on each side in tight contact with the film. 14 15 Single Screen cassette Type of Cassette Double Screen Cassette 16 17 4  8/24/24 Single intensifying Have screen both side screens 2. Double 1.Single Designed to be used Screen Used in double emulsion film screen with a single sided cassette cassette Principal application Principal application in in mammography general radiography 18 19 Intensifying screen (IS) Screen 4 Distinct A device that Construction Layers converts the remnant radiation Protective Coating to light that produces the latent Phosphor image. Reflective Layer They acts as an amplifier of the Base remnant radiation. 20 21 5  8/24/24 Protective Coating Coating is transparent to light. Resistant to abrasion and damage from handling Provide surface for cleaning while protecting the phosphors. 22 23 Phosphor The active layer of intensifying screen. The phosphor emits light when stimulated by the x-rays Used: Calcium Tungstate 24 25 6  8/24/24 Modern screen uses rare earth elements such as: Reflective Layer The light front the phosphor is emitted Gadolinium isotropically Lanthanum Without this layer, only half of the light Yttrium would interact with the film The reflective layer redirects the light to the film. 26 27 Base Luminescence Any material that gives light in The base is the layer farthest from the response to a stimulus is a luminescent material film. (phosphor). 2 types of luminescence: It is usually made of polyester. a. Fluorescence – gives off visible light while the phosphor is being stimulated. b. Phosphorescence – continues to give off visible light even after the radiation exposure has stopped. 28 29 7  8/24/24 Properties of Screens Phosphor composition – rare earth screens Phosphor thickness – The thicker the phosphor layer, the higher the number of x- ray converted to light. High speed screens have thick layer; Detail screens have a thin layer. 30 31 Properties of Screens Crystal Size – Larger the crystals produce more light per interaction; Detail screen have small crystals. Concentration of crystals – the higher the concentration of crystals, the higher the speed. 32 33 8  8/24/24 Rare-earth screen materials: Detective Quantum Efficiency (DQE) - or the ability to absorb the photons (High Z number) (57-71 atomic number) Conversion Efficiency (CE) - amount of light emitted per x- ray. 34 35 Radiographic Film 36 37 9  8/24/24 2 principal components of film 2 principal components of film 1. Base the foundation of radiographic film 2. Emulsion - the heart of the radiographic film primary purpose is to provide a rigid structure onto which the material with which x-rays or light photons the emulsion can be coated from radiographic intensifying screens interact. The base of radiographic film maintains its size and A mixture of gelatin and silver halide crystals. shape during use and processing so that it does not contribute to image distortion It is coated evenly with a layer that is 3 to 5 µm thick 38 39 40 41 10  8/24/24 Gelatin - Its principal function is to Crossover provide mechanical support for silver halide crystals by holding them uniformly The exposure of an emulsion caused by the light dispersed in place. from the opposite radiographic intensifying screen. Silver Halide Crystals - the active Occurs when the screen light crosses the base to ingredient of the radiographic emulsion. expose the opposite emulsion Silver bromide – 98% Silver iodide – 2% Results: Crossover effect - blurring of image Atomic No: (Br = 35; Ag = 47; I = 53) Atomic No: gelatin and the base (for both, Z ≈ 7) 42 43 Image Formation X-ray converted to light photons: LATENT IMAGE - image before processing (invisible image) MANIFEST IMAGE - Visible Image, after proper chemical processing 44 45 11  8/24/24 RT5FIAPIA: FILM - PRELIM SCREEN IMAGE, Processing Room and Design ACQUISITION, PROCESSING AND Processing Room Equipments and Accesories IMAGE ANALYSIS Film Processing 1 2 Radiographic LOCATION Centrally located Processing Room Serviced by hatches from the adjacent imaging room Dark room is a place where the necessary Away from damp or hot areas handling and processing of films can be carried out safely and Accessible in terms of power and water supply efficiently. DARKROOM / Adjoining viewing room PROCESSING ROOM – is a room from which Completely light proof – no windows normal light excluded. 3 4 1  8/24/24 CENTRALLY LOCATED DARK ROOM Complete blackout is unnecessary. Safe illumination is required to facilitate darkroom procedures. It must exclude all outside light and provide safe artificial light. 5 6 PASS BOX / CASETTE HATCH Two light-tight and x-ray proof doors Both cannot be opened at the same time. 7 8 2  8/24/24 Darkroom construction Darkroom Construction Darkroom illumination Minimum floor area is 10 sq m Ceiling Height must be 2.5 m or 3 Darkroom equipment and its arrangement meters Size may reduce depending upon Health and safety in processing area the darkroom needs 9 10 Darkroom floor Relative humidity is maintained at 40- 60%. Non-slip flooring Room temperature maintained between 18-20 degrees Celsius Durable and easy to clean VENTILATION Light colored (low-light AND HEATING A minimum of 10 air changes per hour working conditions) All these conditions can be achieved using a good air conditioning system. 11 12 3  8/24/24 Satisfactory working conditions for the staff Adequate processing conditions X-ray apparatus in the Radioactive adjacent room should VENTILATION be properly placed – materials should be AND HEATING Efficient automatic processor performance stored as remotely primary beam never be directed at the as possible from darkroom wall. the darkroom. Adequate removal of stale humid air and supply of fresh air Intake and extract fans can be used 13 14 TYPE OF ENTRANCE RADIATION PROTECTION Walls adjacent to the radiographic rooms should be Single door system shielded with correct thickness of the lead - 1.6 – 2 mm lead or its equivalent: Double door system Ø25mm high quality barium plaster Ø225 mm thick single brick wall Maze and Labyrinth Ø150 mm thick concrete Revolving door system 15 16 4  8/24/24 SINGLE DOOR ENTRANCE D/A: This type of door can Latch or lock from inside cause Capable of releasing accidental the lock from outside in case of emergency exposure of Ideally no one should film to white work alone in a dark room light. 17 18 DOUBLE DOOR DOUBLE DOOR ENTRANCE It has two doors One leading in and other out with a short hallway in between. 19 20 5  8/24/24 Maze Entrance MAZE TYPE ENTRANCE Has no doors People can enter and exit at any moment 21 22 LABYRINTH TYPE ENTRANCE Advantages of labyrinth: Black paint for the interior of the passages Easy access to darkroom Matte black paint Vertical height- 2m No hazard to single handed operator Length – not less than 3 m Width – not more than 700mm Safelight fitted along the Allows air circulation passageway 23 24 6  8/24/24 REVOLVING DOOR ENTRANCE The most eficient but most expensive type of door. 3 feet in diameter. Lightproof access to the room. 25 26 For inspection & maintenance of DARK ROOM ILLUMINATION cassettes & screens Cleaning of work surfaces WHITE Servicing of equipment, LIGHT changing solutions Sited close to the ceiling ; White lighting Safe lighting Preferably centrally placed Moderate in intensity (60w tungsten, 30w fluorescent ) 27 28 7  8/24/24 Used in conjunction SAFE LIGHT with a 25 W lamp A source of light which will not fog the films and still provide adequate illumination under processing conditions. SAFE Extremes of heat and moisture deteriorates Consists of a lamp fixture in which a pearl bulb of 25 W is used with a colored filter placed in front of the LIGHT the filter bulb However no safe light is completely FILTERS Should be cleaned safe – depends on wavelength periodically /color , intensity of light and duration of exposure. 29 30 SAFELIGHT FILTERS Direct Safelighting Light from the safe lamp directly falls Sheet of gelatin dyed on the working surface in appropriate colour Minimum distance and sandwich of 1.2 m from the between two sheets working surface glass for protection Best for loading and unloading of films 31 32 8  8/24/24 Indirect Safelighting Directs the light towards When the white light passed the ceiling which reflects through the filters of safelight, it corresponds to the color of the light back into the room. How does filters to be transmitted. Intented to provide general illumination to the safelight darkroom work Therefore, correct matching of Suspended atleast 2.1 safelight filter to film is above the floor level necessary. 33 34 WITH NO SAFELIGHTING SAFELIGHTING 35 36 9  8/24/24 SAFELIGHTING HANDLING TIME Identification of Maximum time a film can be exposed to safelight during a procedure without respective causing any appreciable degree of fogging switches is average time: 20-45 secs important. 37 38 DARKROOM 1. MANUAL LAYOUT AND PROCESSING EQUIPMENTS PROCESSING APPARATUS 2.AUTOMATIC PROCESSING 39 40 10  8/24/24 MANUAL PROCESSING UNIT MATERIAL – PVC /Stainless steel 41 42 AUTOMATIC PROCESSOR 1. DRY BENCH LOADING BENCH 2. WET BENCH 43 44 11  8/24/24 DRY BENCH Wet Bench The dry bench is where the cassettes are unloaded and The wet bench is where the processing of the loaded with fresh film. films is carried out. The top of the dry bench must be large enough to accomodate the large cassettes in use when opened out. The usual method is to use a set of tanks holding The top surface must be should either be with wood or a developer, rinse water and fixer, and a large linoleum. tank for washing of films. It is usual to store film boxes, especially those current use, beneath the dry bench , either a cupboard (protected if near x-ray set), or in a film hopper. 45 46 47 48 12