Film-Screen Image Acquisition, Processing and Analysis PDF

PRELIM Film-Screen Image Acquisition, Processing and Analysis | IT-RAD 104 | 23 Prepared by: CMITSC Academics Committee; H.Pepito Disclaimer: Inform...

PRELIM Film-Screen Image Acquisition, Processing and Analysis | IT-RAD 104 | 23 Prepared by: CMITSC Academics Committee; H.Pepito Disclaimer: Information may not be complete | References: PPT, Handouts 24 LECTURE 2: MEDICAL X-RAY FILM FILM CONSTRUCTION It remembers that it is made Chemical memory flat, and it will come out as Medical X-ray film is the First Recording Medium used to flat (1D) produce radiographic image. It can cause negative impact Non-flammable to the health if it is burned It needs to be waterproof Waterproof because it goes through chemicals Blue tinted it lessens eye strain Adhesive (Substratum) Layer Thin coat of gelatin which acts as the adhesive layer Base which sticks the emulsion to the base material. Provides uniform adhesion and proper contact and Foundation for the x-ray film integrity of the base and emulsion during use and The center and the largest portion of the film processing Provides a rigid structure where the emulsion is coated Only a few molecules thick 150 to 300 μm thick In between the base and emulsion. History: Emulsion Layer Glass plate (breakable) – it is heavy Is the sensitive material use to record the image and is Cellulose Nitrate (flammable) – 1920’s to early made up of suspension of light sensitive salts (Silver halide 1930’s, an incident happened in the hospital wherein a crystals) and gelatin binder. fire broke out o Silver halide crystal is the principal material used Cellulose Triacetate (also called safety base – thick for film emulsion compared to polyester) – 1960’s, it is too thick and Most important part of the x-ray film according to Bushong. when it is processed it is still wet and a stain will be Where the layer of the x-ray film that records the image. visible in the next viewing The heart of x-ray film Polyester (modern film base) - more resistant, much thinner, flexible, and dimensionally stable maintaining Approximately 5x10-6 m its original state and size even after multiple 2 Silver Halide Crystals used for x-ray type film: processing. o Silver Iodide (AgI) - added to AgBr to increase the natural sensitivity of the x-ray film to light CHARACTERISTICS OF A GOOD BASE MATERIAL o Silver Bromide (AgBr) - is used alone maintaining original size o AgBr + AgI = IodoBromide crystal Dimensional stability regardless of multiple processing Optical clarity/uniform it needs to be clear because Supercoat (Overcoat) lucency it is viewed via negatoscope. Thinner while maintaining its Hardened gelatin strength. Minimizes its the protective layer of the film which allows the film to be High tensile strength parallax error, the apparent handled and protects the emulsion layer of the film displacement of your image as seen in the radiograph Flexibility to prevent snapping Inert to processing It will not change regardless chemicals of multiple processing DE LA SALLE MEDICAL AND HEALTH SCIENCES INSTITUTE - COLLEGE OF MEDICAL IMAGING AND THERAPY 4  PRELIM Film-Screen Image Acquisition, Processing and Analysis | IT-RAD 104 | 23 Prepared by: CMITSC Academics Committee; H.Pepito Disclaimer: Information may not be complete | References: PPT, Handouts 24 ELECTROMAGNETIC SPECTRUM AgBr has a natural sensitivity that ends at the blue region of the visible spectrum (480 nm). Is the range of frequencies over which an electromagnetic The addition of 2% - 4% of silver iodide marginally improved radiation can be propagated the film’s sensitivity (530 nm). The shorter the wavelength the higher the energy The blue sensitive film is compatible with calcium tungstate IS which emits blue light. Spectral Sensitizing In 1970's another IS was introduced, the rare earth screen which primarily emits green light. But no film was compatible. A process introduced by Vogel in 1870's known as spectral sensitizing was adopted to create films with increased sensitivity. VISIBLE SPECTRUM Spectral Sensitizing is the Is the range of wavelengths of the electromagnetic process of extending the spectrum over which an unaided human eye can perceive sensitivity of AgBr crystal by wavelength changes as an alteration in color coating the surface of the Ranges from 400nm to 700nm crystal with one or more layers Xray film is naturally sensitive to around the energy of of dye. 480nm or the blue region of the visible spectrum The longer wavelength green light is absorbed at the surface Visible Light Region of the Electromagnetic Spectrum of the crystal and transferred its energy to the crystal itself. The longer the wavelength, the lower the energy is, and more layers of dye is added as it is more sensitive to the other color of the wavelength TYPES OF FILM ACCORDING TOSENSITIVITY MONOCHROMATIC SPECTRAL SENSITIVITY Is the range of wavelength of the electromagnetic radiation Blue Sensitive that the film will respond. Compatible with calcium Spectrogram - the diagrammatic representation of the tungstate screen spectral sensitivity of your silver bromide crystal no longer used today No longer used because it is hard to manufacture the calcium tungstate screen. The peak of the spectral sensitivity is at 400nm, which is a high sensitivity at blue region Made from AgBr and AgI without dye on its surface Peak Sensitivity - the wavelength which the film is most sensitive to. Reaching it, there will be a rapid decline. Cut-off Sensitivity - the wavelength in which the film is no longer sensitive. DE LA SALLE MEDICAL AND HEALTH SCIENCES INSTITUTE - COLLEGE OF MEDICAL IMAGING AND THERAPY 5  PRELIM Film-Screen Image Acquisition, Processing and Analysis | IT-RAD 104 | 23 Prepared by: CMITSC Academics Committee; H.Pepito Disclaimer: Information may not be complete | References: PPT, Handouts 24 ORTHOCHROMATIC Advantages of Tabular Grain 1. Increases resolution due to reduction in cross-over – Green Sensitive o it is because the dye coated on the surface of the Used with gadolinium tabular grain is more effective in absorbing the light oxysulfide IS or the rare photons. When it is absorbed, there would be lesser earth amount of light to pass through the material and currently the most interacts with the 2nd emulsion. commonly used type of o Reduces the cross-over approximately 35% thus film the image perceived is very sharps The peak is around 550nm, which is at the green region sensitivity PANCHROMATIC Sensitive to all colors of the visible spectrum Not popular Has to be processed in total darkness no longer used today 2. Reduction in silver coating weight - The less the silver, because it is hard to the less expensive and faster processing manufacture this type of 3. Suitable for 45s processing film There is no advantage because there is no IS that emits Grain Size and Distribution light in the green region wavelength Its peak is around 590nm, which is the green to yellow Grain size and distribution affect the following: region 1. Contrast. Affected by size distribution. The more sizes GRAIN TECHNOLOGY available in the film, the lower is the contrast. 2. Speed. The bigger the average grain size, the higher the Types of Grain speed of the film. o One above from the base + fog, measure of the 1. Globular Grain effectivity of your x-ray film that will produce the spherical in shape and has a bigger volume. Use for necessary density of the exposure. blue sensitive film. o Usual average grain size is 1𝝁m All monochromatic are the globular grain 3. Graininess. Is the apparent clumping of crystals as seen 2. Tabular Grain on the radiograph. The bigger the crystals, the higher the has a table-top like structure that provides bigger graininess of the film surface are but smaller volume. Tabular grain is for the Orthochromatic BINDER Type of photographic film that includes all color of films, It binds the silver halide crystals and allow it to be coated and many black and white unto the base History: Collodion first binder use. A mixture of gun-cotton, ether, and alcohol. Collodion is introduced by Frederick Scott Archer in 1851 It remained wet during exposure and development, this is the reason it was called “wet film” DE LA SALLE MEDICAL AND HEALTH SCIENCES INSTITUTE - COLLEGE OF MEDICAL IMAGING AND THERAPY 6  PRELIM Film-Screen Image Acquisition, Processing and Analysis | IT-RAD 104 | 23 Prepared by: CMITSC Academics Committee; H.Pepito Disclaimer: Information may not be complete | References: PPT, Handouts 24 Gelatin B. Direct Exposure Film (Non-screen type of film) from the word “gelata” which means formation in water. It Directly exposes which doesn't require IS and uses comes from the collagen fiber in which the primary carboard film holder. sources are the cartilage, skin, and the protein matrix It produces higher resolution because it eliminates the (ossein) of the bones of animals. It is the modern binder screen unsharpness used. Requires higher exposure factor typically 10 – 100 o Hydrolysis - process of extracting gelatin from times in comparison with the IS animals higher resolution image Gelatin introduced in 1871 by Richard Leach Maddox requires higher exposure factor typically 10 to 100 Also called gelatin silver bromide dry plate. times compared to screen film has thicker emulsion layer takes longer to process BASIC FILM TYPES was used to image thin body structures with high Duplitized or Double-Emulsion. subject contrast and present low radiation risks no longer used today These are films that have emulsion layer coated on both sides of the film base. Single-Emulsion Films The most commonly used type of film still being used today. Films that have emulsion layer coated on only one side of Used for conventional radiography. the film base. The two emulsion layers which increases the speed of the It had many uses when it was first introduced: It was used film thereby reducing the exposure needed for every together with a multi-format camera, or most special examination which results in much lower patient dose. imaging modality Also results Cross over and parallax error. It is no longer used today unless for conventional There are no notch and the film is whole mammography Has a notch in the film A. Screen Type Film used with IS. o Ultrasound i. Contrast (standard) type o Nuclear Medicine Produces high contrast image o CT Scan Used for most general radiographic examination o MRI Contains relatively uniform grain size o DSA Most common type of film used in the Philippines o Mammography o Cardiovascular Angiography ii. Half-speed o Photofluoragraphy Made of finer grains and therefore produce fine detail Anti-curl images o prevents the curling of film during the processing Low speed o When the gelatin from the emulsion layer swells Requires twice the amount of exposure of the contrast because of its absorption of water and solution, type film the layer of gelatin on the other side also does the Made in comparison with the contrast type film same which prevents the curling of the film Anti-Halation Layer iii. Latitude o is the dye added to the gelatin has wider latitude o will effectively absorb the light photons that have produces low contrast image already passed through the emulsion layer made with many grain sizes most compatible for CXR examination Made in comparison with the contrast type film DE LA SALLE MEDICAL AND HEALTH SCIENCES INSTITUTE - COLLEGE OF MEDICAL IMAGING AND THERAPY 7  PRELIM Film-Screen Image Acquisition, Processing and Analysis | IT-RAD 104 | 23 Prepared by: CMITSC Academics Committee; H.Pepito Disclaimer: Information may not be complete | References: PPT, Handouts 24 FILM FORMATS AND PACKAGING Should not be placed with objects above it as the pressure at the middle will cause it to crease Standard Sizes Other Sizes Packaging If it is too cold, it will cause fog, and if it’s too hot, it will (inches) cause staticity 8 x 10 8 x 12 Available in 25, 50, 100 10 x 12 12 x 14 and 500 sheets 11 x 14 4x4 AFW (Alternate Folded 14 x 14 70mm roll film Wrapped) – has a paper in between the films 14 x 17 35mm film w/ NIF (Non Interleaved perforation Films) – consecutive films DIFFERENCE IN THE COLOR OF THE FILMS VIOLET is exposed to white light but not processed BLUE is exposed to white light but expired, green sensitive film, not processed GREEN is exposed to white light but expired, blue sensitive film, not processed CLEAR BLUE Not exposed to any light but processed BLACK exposed to white light but processed HANDLING AND STORAGE Handling Hands must be clean, dry & free of lotions, and other contaminants Films should be handled carefully by the edges to avoid physical strains such as pressure, creasing, or buckling. Film bin, when opened, the closest is the biggest sized film Storage Films should be stored vertically and not horizontally. Try to maintain an even temperature on the storage area. o 10 degrees - longer than 3 months o 20 degrees - if less than 3 months Make sure that the storage is not damp. A value of 50% relative humidity should be aimed for. Avoid storing photographic chemicals in the same area as the film. Fumes and certain types of paint can fog the film. Mercury vapor can fog film. Do not use mercury thermometer in processing room. Films should be stored away from the source of radiation. It should not exceed 7μR/hr. Use the first in, first out principle (FIFO) DE LA SALLE MEDICAL AND HEALTH SCIENCES INSTITUTE - COLLEGE OF MEDICAL IMAGING AND THERAPY 8