RADIOGRAPHIC TECHNIQUE 1 Film Screen Image Acquisition, Processing, and Analysis Group 1: Bachar, Kate Abigail P., Gambalosa, Christine Shaira C. & Hernandez, Renz Aldrin D. TOPICS TO BE DISCUSSED: I. Medical X-ray Film II. Intensifying Screens III. Film Holders IV. Darkroom V. Latent Image Formation VI. Processing of Latent Image VII. The Processing Solutions VIII. Sensitometry MEDICAL X-RAY FILM Cross-sectional structure of a double emulsion or a duplitized film. At the center and the largest portion of the film is the film base. And coated on both sides of the film base are the emulsions. Those two are the major parts of the x-ray film. Other parts are the adhesive layer and the supercoat or overcoat which is the protective coating of the film. OLPMC – Batch 2022A BASE Foundation of the x-ray film Provide a rigid structure for the emulsion to be coated 150 to 300 μm thick History: - Glass plate Radiologists used to refer to radiographs as x-ray plates. During WWI, high-quality glass became largely unavailable while medical applications of xrays particularly by the military, were increasing. Breakable - Cellulose nitrate Flammable Improper storage and handling of some x-ray films files resulted in severe hospital fires during the 1920s and early 1930s. - Cellulose triacetate It is a film with safety base. It has properties similar to cellulose nitrate but is not as flammable. - Polyester Is introduced soon after the cellulose triacetate and became the modern film base. Compared to cellulose triacetate, it is more resistant to warping and is stronger. It is also thinner and dimensionally stable. Characteristics of a Good Base Material - Dimensional Stability Meaning it should be able to maintain its size and shape RADIOGRAPHIC TECHNIQUE 1 Film Screen Image Acquisition, Processing, and Analysis Group 1: Bachar, Kate Abigail P., Gambalosa, Christine Shaira C. & Hernandez, Renz Aldrin D. - - - - - - during use and processing so that it does not contribute to image distortion/ prevents unnecessary bending which could cause artifact. Optical clarity/Uniform lucency This is because radiographs are viewed in a negatoscope using transmitted light. And light should be able to pass through the base material. Likewise, the transparency should be uniform all throughout the base material. Uneven density may be misinterpreted as pathology. High tensile strength It can be made thinner while maintain its strength. It is important because a thin base material minimizes the parallax error. Parallax error is the apparent displacement of image seen on the radiograph. Flexibility Required for ease of handling and because film are snapped into the negatoscope. Inert to processing chemicals It should not be change in form when processed. Chemical memory That it remembers that it is made flat. That after it passes in and out through the automatic processor, it comes out flat. Non-flammable Water-proof - OLPMC – Batch 2022A Blue-tinted Dye is added to the base of most radiographic film to slightly tint the film base. Compared with untinted film, this coloring reduces eyestrain and fatigue, enhancing the radiologists’ diagnostic efficiency and accuracy. ADHESIVE LAYER (SUBSTRATUM LAYER) Thin coat of gelatin Ensures uniform adhesion of the emulsion to the base Between the emulsion and the base is a thin coating of material (gelatin) It allows the emulsion and the base to maintain proper contact and integrity during use and processing. SUPERCOAT (OVERCOAT) Hardened gelatin Essential for protection of the film surface Protects the emulsion from scratches, pressure, and contamination during handling, processing, and storage. EMULSION Heart of the radiographic film Most important part of the x-ray film because it is the layer that records the image. It results in the sensitivity of x-ray film to light and x-ray photons. Contains silver halide crystals suspended in a layer of gelatin. The principal function of gelatin id to provide mechanical support for silver halide crystals by holding them uniformly dispersed in place. RADIOGRAPHIC TECHNIQUE 1 Film Screen Image Acquisition, Processing, and Analysis Group 1: Bachar, Kate Abigail P., Gambalosa, Christine Shaira C. & Hernandez, Renz Aldrin D. - Silver halide crystals are sand-like granules distributed throughout the emulsion. It is also the active ingredient of the radiographic emulsion. o Silver Iodide (Agl) o Silver bromide (AgBr) Can be used alone as a silver halide crystal but not the silver iodide. Silver iodide is only added silver bromide crystal to increase its natural sensitivity to light. Silver iodide and silver bromide crystals is also called iodobromide crystals. SPECTRAL SENSITIVITY - Cut-off sensitivity Is the wavelength beyond which the film is no longer sensitive. As seen on the spectrogram, the silver bromide crystal has a peak sensitivity at about 430 nm and cut-off sensitivity at around 480 nm. The addition of 2%-4% of silver iodide marginally improved the film’s sensitivity (530 nm). Both wavelengths are in the blue region of the visible spectrum. This means also that silver bromide crystal is no longer sensitive to green, yellow, orange, and red color wavelengths. All silver halide films respond to violet and blue light but not to green, yellow, orange, and red color. Calcium tungstate screens emits blue and violet visible light, but it has been replaced with rare earth screens which emit ultraviolet, blue, green, and red light. - Is the range of wavelength of the electromagnetic radiation that the film will respond. In other words, it refers to the color of light to which a particular film is most sensitive. Peak Sensitivity Is the wavelength in which the film will exhibit its highest response Is the wavelength in which the film is the most sensitive After reaching the peak sensitivity, there is a rapid decline in the sensitivity of the film until it reaches the cut-off sensitivity. OLPMC – Batch 2022A SPECTRAL SENSITIZING A process introduced by Vogel in 1870’s was adopted to create films with increased sensitivity (sensitivity to green light and other long wavelengths lights). RADIOGRAPHIC TECHNIQUE 1 Film Screen Image Acquisition, Processing, and Analysis Group 1: Bachar, Kate Abigail P., Gambalosa, Christine Shaira C. & Hernandez, Renz Aldrin D. Achieved by coating the surface of the crystal with one or more layers of dye. Spectral emission Refers to the color of light produced by a particular intensifying screen. When radiographic film is used with intensifying screens, it is important to match the spectral sensitivity of the film with the spectral emission of the screens. An incorrect match of film and screen based on spectral emission and sensitivity results in radiographs that display inappropriate levels of radiographic density. TYPES OF FILM ACCORDING TO SENSITIVITY Monochromatic - blue sensitive film - compatible with calcium tungstate screen which emits blue light - no longer used today Orthochromatic - Green sensitive film - Currently the most commonly used type of film - Used with gadolinium oxysulfide intensifying screen Panchromatic film - Sensitive to all color of the visible spectrum - Not popular - Has to be processed in total darkness - No longer used today - Used in photography TYPES OF GRAIN *Before spectral sensitizing was introduces, grains are all globular. OLPMC – Batch 2022A Globular Grain – spherical in shape and has bigger volume. Used for blue sensitive film. Tabular Grain – has a table-top like structure that provides bigger surface area but has small volume. Advantages of Tabular Grain Increases resolution due to reduction in cross-over It is because the dye coated in the surface of the tabular grain is more effective in absorbing light photons. When light is more effectively absorbed by the dye, there would be lesser light to pass through the base material and interact with the second emulsion. Reduction in silver coating weight Reduces the manufacturing cost of the film Means lesser silver to convert and therefore lesser time to process Suitable for 45 s processing GRAIN SIZE AND DISTRIBUTION Grain size and distribution affect the following: RADIOGRAPHIC TECHNIQUE 1 Film Screen Image Acquisition, Processing, and Analysis Group 1: Bachar, Kate Abigail P., Gambalosa, Christine Shaira C. & Hernandez, Renz Aldrin D. Contrast. Affected by size distribution. The more sizes available in the film, the lower is the contrast. Speed. The bigger the average grain size, the higher the speed of the film. Graininess. Graininess is the apparent clumping of crystals as seen on the radiograph. The bigger the crystals, the higher the graininess of the film. BINDER Binder binds the silver halide crystals. History - Collodion – first binder use. A misture of gun-cotton, ether, and alcohol. Introduced by Frederick Scott Archer in 1851. Remain wet during exposure and development. - Gelatin – from the word “gelata” which means formation in water. It comes from the collagen fiber in which the primary sources are the cartilage, skin and the protein matrix (ossein) of bone of animals. It is the modern binder use. Introduced by Richard L Maddox in 1871. BASIC FILMS ACCORDING TO CONSTRUCTION Duplitized or double emulsion - These are films that have emulsion layer coated on both sides of the film base. - Used for conventional radiography. - Screen type film – used with intensifying screen o Contrast type - Produces high contrast image - Used for most general radiographic examination - Contains relatively uniform grain size OLPMC – Batch 2022A Most common type of film used in the Philippines o Half-speed - Made of finer grains and therefore produce fine detail images - Low speed - Requires twice the amount of exposure of the contrast type film o Latitude - Has wider latitude - Produces low contrast image - Made with many grain sizes - Most compatible for chest x-ray examinations - Direct Exposure film (non-screen type) - Higher resolution image - Require higher exposure factor typically 10 to 100 times compared to screen-film - Has thicker emulsion layer - Takes longer to process - Recommended for thin body structures with high subject contrast and present low radiation risks Single-emulsion Film - Films that have emulsion coated on one side of the base only. - Some manufactures use absorbing dyes to prevent photons, particularly light from striking adjacent silver halide crystals. While some use an antihalation backing which prevents the ”bouncing around” of light photons as the screens fluoresce, thus improving the image sharpness. - Uses: - Ultrasouns - NM - CT - MRI - DSA - Mammo - RADIOGRAPHIC TECHNIQUE 1 Film Screen Image Acquisition, Processing, and Analysis Group 1: Bachar, Kate Abigail P., Gambalosa, Christine Shaira C. & Hernandez, Renz Aldrin D. - Cardiovascular Angio Photofluorography FILM FORMATS AND PACKAGING Standard sizes (in inches) - 8x10 - 10x12 - 1x14 - 14x14 - 14x17 Other sizes - 8x12 in - 12x14 - 4x4 - 70 mm roll film - 35 mm film with perforation Packaging - Available in 25, 50, 100, and 500 sheets - AFW (Alternate Folded Wrapped) - NIF (Non-Interleaved Films) HANDLING AND STORAGE OF FILM Anyone who handles the film should be careful not to bend, crease, or subject it to rough handling. Clean hands are a must, and hand lotions should be avoided. Improper handling can cause artifacts that interfere with diagnosis. Films should be stored vertically and not horizontally. Radiographic films should be stored in a cool, dry place and at temperatures lower than approx. 20°C. If the film s are to be stored for longer than 3 months, the ideal temperature is 10°C. *Radiographic film is sensitive to the effects of elevated temperature and humidity. Heat increases fog, therefore, reduces contrast. OLPMC – Batch 2022A A value of 50% relative humidity should be aimed for. *elevated humidity also increases fog and therefore reduces contrast, while storing film in an area that is too dry can cause static artifacts. Films should be stored away from the source of radiation. Films should be stored vertically. Use the first in, first out principle. Thirty days is a reasonable maximum storage time for radiographic film. Films should be stored and handled in the dark. The storage bin should have an electrical interlock that prevents it from being opened while the door to the darkroom is open. dow RADIOGRAPHIC TECHNIQUE 1 Film Screen Image Acquisition, Processing, and Analysis Group 1: Bachar, Kate Abigail P., Gambalosa, Christine Shaira C. & Hernandez, Renz Aldrin D. OLPMC – Batch 2022A INTENSIFYING SCREEN Cardboard- or plastic-base structures, usually found as pairs inside the cassette. A device that converts x-rays to visible light. It amplifies the effect of image-forming x-rays that reach the screen-film image receptor. HOW? The intensifying screens contain phosphors that cause luminescence or light to be given off from the screens at the time of the exposure. This light helps to produce the image on the film. *(because x-ray film is sensitive to x-rays and light). Advantages of using intensifying screens: reduces patient dose, short exposure time, less motion unsharpness, less thermal stress on the x-ray tube, reduce shielding required Disadvantages: causes screen unsharpness that results to poor resolution *(more of the xray photons will interact with the screens phosphor than directly with the emulsion of the x-ray film.) Cross-sectional view of an intensifying screen showing its four basic components: base, reflective layer, phosphor, and protective coating. PROTECTIVE COATING The layer that is closest to the x-ray film. 10 to 20 μm thick and is made of cellulose acetobiturate It serves to protect the phosphor layer from abrasion and damages during use and cleaning. It also eliminates the buildup of static electricity. PHOSPHOR The active layer of the intensifying screen. 50 to 300 μm thick RADIOGRAPHIC TECHNIQUE 1 Film Screen Image Acquisition, Processing, and Analysis Group 1: Bachar, Kate Abigail P., Gambalosa, Christine Shaira C. & Hernandez, Renz Aldrin D. Phosphors used in intensifying screens should be capable of luminescence, which means “ the ability to give off light.” The glow of the light from the screens is called fluorescence. It is the emission of light as a result of exposure to radiation. Afterglow or phosphorescence is the glow of light after the exposure has stopped. It is undesirable because it results to darkening on the film. Two types - Calcium tungstate o Discovered by Thomas Edison in 1896. o Emits lights in the violet-to-blue region. - Rare earth o Introduced by Wickersheim, Alves, and Buchanan in 970s. o Rare earth phosphors are more efficient in converting x-ray energy to light. o It needs less x-ray energy to provide the same energy conversion as calcium tungstate. REFLECTIVE LAYER *Situated between the phosphor and the base Approx. 25 μm thick Made of white shiny substance such as magnesium dioxide or titanium dioxide. Intercepts light headed in other directions and redirects it towards the film. It enhances the efficiency of the intensifying screen, nearly doubling the number of light photons that reach the film. OLPMC – Batch 2022A BASE Thickest part of the intensifying screen The layer farthest from the radiographic film 1 mm thick It provides support for the phosphor layer. Made of polyester *(because of its flexibility and durability); *(Old material used was cardboard) SCREEN SPEED A relative number that describes how efficiently x-rays are converted to light. Film and screen should be matched to provide maximum. Calcium tungstate screens have speed approx. 50-200 while rare earth screens have aped approx. 80-1200. A high-speed value means less exposure is needed to produce a radiograph with adequate density. CARE OF SCREENS It should be handled with care. Screens should be examined regularly. It should be cleaned on a regular basis with an antistatic cleaner. RADIOGRAPHIC TECHNIQUE 1 Film Screen Image Acquisition, Processing, and Analysis Group 1: Bachar, Kate Abigail P., Gambalosa, Christine Shaira C. & Hernandez, Renz Aldrin D. OLPMC – Batch 2022A FILM HOLDERS Are also called cassettes. The cassette is a light-tight device that is used to transport the x-ray film for use without exposing the film to room light. The front cover is the exposure side of cassette. It has an ID blocker designed for patient identification Made of thin radiolucent material such as aluminum or plastic made of resin. Modern cassettes are made of carbon material. The back cover is made of heavy metal to minimize backscatter. X-ray Flexible cassettes *Fitted to body curves for radiography of joints, cervical vertebrae, and jaws. Cardboard Holders SPECIAL TYPE OF CASSETTES Curved cassettes *Anatomically designed for accurate filming ok knee, neck, lateral cervical spines, mandible, and sinuses Dental cassettes *Light proof pouches made of high quality tear-resistant vinyl and will stand up to the day to day usage. RADIOGRAPHIC TECHNIQUE 1 Film Screen Image Acquisition, Processing, and Analysis Group 1: Bachar, Kate Abigail P., Gambalosa, Christine Shaira C. & Hernandez, Renz Aldrin D. OLPMC – Batch 2022A Laser imager cassettes *Holds x-ray film for exposure by imager Mammography cassettes *Designed to provide high resolution images for mammography Grid Cassettes *Cassette mounted with grid material used for portable radiography and decubitus positions of body parts that need grid.
