Darkroom Equipments 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