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DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Developer V Fixer CRT04105 · Radiographic Imaging Sciences START READING NOTES Study Developer V Fixer using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. Contents of This Topic Developer V Fixer Film processing involves the following procedures : The developing solution contains four component , all dissolved in water: Preservative : Fixing solution Fixing solution also contains four components : Washing It depends on ; 1- Light tight room through the use of a maze or a light tight door . It is a low – intensity light composed of long wavelength in the red – orange portion of the visible light spectrum . 1- Manual or wet processing : After developing , the film is rinsed in running water ,then the film is put in the fixer solution . It is alternative to manual processing . The x- ray film is presented in a special sachet containing developer & fixer . IMAGE CHEMICAL PROCESS Developer V Fixer When a beam of photons exits an object and exposes an x-ray film, it chemically changes the photosensitive silver halide crystals in the film emulsion. These chemically altered silver bromide constitute the latent image (invisible) on the film. Exposure to radiation chemically alters the photosensitive silver halide crystals to produce the latent image .Processing the exposed film in developer and fixer convert the latent image into the visible radiographic image . Formation of the Latent image Film processing involves the following procedures : 1- Immerse exposed film in developer 2-Rinse film in water bath 3-Immerse film in fixer 4-Wash film in water bath 5-Dry film Developer V Fixer The developer reduce all silver ions in the exposed crystals of silver halide (those with a latent image ) to metallic silver grains . Areas with many exposed crystals are denser because of their higher concentration of black metallic silver grains after development .If the developer remains too long in contact with silver bromide halide crystals that do not contain a latent image , it slowly reduces these crystals also , thereby overdeveloping the image . Developing solution The developing solution contains four component , all dissolved in water: Developer or reducing agents Convert the exposed silver halide crystals to black ,metallic silver grains. Activator or accelerator : It softens and swells the emulsion so that the developing agents can reach the crystals more effectively , it also provides the necessary alkaline environment for the developing agents. Restrainer: Prevent the developer from developing unexposed crystals and keep the image from appearing fogged ( dull , gray ,and lacking in contrast ). Preservative : Prevents oxidation of the reducing agents in the developer in order to prolong the effectiveness of the chemicals . Developer V Fixer After development , the film emulsion swell and becomes saturated with developer . At this point the film are rinsed in water for 30 seconds before they are placed in the fixer . Rinsing dilutes the developer , slowing the development process . It also removes the alkali activator , preventing neutralization of the acid fixer . This rinsing process is typical for manual processing but is not used with automatic processing . Rinsing Fixing solution The primary function of fixing solution is to dissolve and remove the undeveloped silver halide crystals from the emulsion . The presence of unexposed crystals causes film to be dark . A second function of fixing solution is to harden and shrink the film emulsion. Fixing solution also contains four components : Fixing or clearing agent : It remove (by dissolving ) unexposed , undeveloped silver halide crystals from the emulsion Acidifier : Helps to terminate the developing process by neutralizing the alkaline developer . It also provides the necessary acid environment required by the fixing agent. Hardener : Shrink and hardens the emulsion after it has been softened by the activator in the developing solution . Preservative Prevent chemical deterioration of fixing solution Washing A washing step is necessary to remove all excess chemicals from the emulsion . Developer V Fixer Is the area which the films must be process , because radiographic film is sensitive to visible light , so processing must be conducted in an area of relative darkness. Darkroom It depends on ; 1- Types& amount of the films to be processed . 2- Number of persons working in the darkroom ( if one person works in the darkroom , 9×9 feet is recommended to process dental radiograph ,while 20×20 feet of floor space is recommended for more than one person . Size of the darkroom : Developer V Fixer 1- It should be located in the cool part of the office ,since the best processing is achieved at 68 f , and the film should be stored in a cool place 2- It should be approachable from the rooms where the films are to be exposed and examined . 3- The temperature of the room should fluctuate as little as possible , since the temperature of the processing solution must be kept constant . 4- Consideration should be given to the humidity ,since extreme humidity retards drying of the processed films , and damages unused films stored in open boxes , while low humidity can cause static electricity problem Location of the darkroom : 1- Light tight room through the use of a maze or a light tight door . 2- The surface of the room should be able to resist chemicals of processing . The floor should be waxed to be protect from chemicals and wall colors should be light enough to reflect the safe light . : 3- The illumination of the darkroom is consists of two types a)Ordinary white b)Safe light Construction and design It is a low – intensity light composed of long wavelength in the red – orange portion of the visible light spectrum . Safe light provides sufficient illumination in the darkroom to carry out processing activities

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Automatic Processing CRT04105 · Radiographic Imaging Sciences START READING NOTES Study Automatic Processing using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. Automatic Processing RADIOGRAPHIC IMAGING SCIENCES AUTOMATIC FILM PROCESSING Makes use of automated machine for chemical processing of the films. In automatic processing machines, the exposed film is fed at one end and it passes successively through developer, fixer, washing and drying sections. The machines make use of roller system for the transport of film. The film comes out through the other end of the processor, processed, dry and ready for viewing. The Systems of An Automatic Processor The film feed section The transport system Temperature control system Recirculation system Replenishment system Dryer system Electrical systems 1.The film feed section When no films are being processed, an automatic processor is normally in what is known as a stand-by condition, with certain system functions such as the roller drive inactive. As a film is fed to the processor, so the cycle of events listed below is initiated: (l) Drive motor energized (to turn the rollers). (2) Safelight above feed tray extinguished. (3) Developer and fixer replenisher pumped into tanks. (4) Drier heater energized. (5) Wash water now rate boosted. (6) Film signal delay timer activated (audible signal which will sound 1-3 s after the trailing edge of the film has passed the entry rollers, to let the operator know that the next film can be fed to the processor). 2.The Transport System The film to be processed is placed on the input tray and gently advanced until taken up by the entry rollers. It is then automatically transported via a system of rollers and/or guide plates in and out of developer, fixer, wash and drying sections of the processor in turn, to be delivered finally to the output tray, dry and ready for viewing NB: Squuege rollers; which are sited between the tanks, help to remove solution from the emulsion as the film leaves one tank and enters another.3.The Temperature Control System 4.The Recirculation System Is a system which ensures that the developer solution is continuously on the move to enable adequate agitation. Adequate agitation of solution is important in achieving satisfactory mixing of the chemical solution and thereby obtaining correctly processed films. While the actual movement of the rollers does provide some movement of the solution, the principal contributor is the recirculation system.5.The Replenishment System The purpose of replenishment; (I) To maintain consistent developer and fixer solution activity. (2) To maintain a constant volume of developer and fixer solution In automatic processors there is little carry-over of chemical solution from one tank to the next because of the effectiveness of the squeegee rollers sited between solutions.• Thus, the principal reason for replenishment in an automatic processor is point (1) above. How replenishment takes place Each time a film is fed into the processor, the entry roller detection system triggers off the replenishment pumps, and replenisher solutions are pumped to the developer and fixer tanks in the processor. The fresh solutions are rapidly and thoroughly mixed with 'old' chemistry, partly due to the action of the rotating rollers but in particular due to the recirculation activity. Excess developer and fixer solution overflow to drain and silver recovery system, respectively. Thus, both solution activity and solution level are maintained. Factors which affect the replenishment rate. (1) Area of film processed. (2) The type of emulsion. (3) The type of image. (4) Aerial oxidation. (5) Orientation of film.6.The Dryer System In order to facilitate rapid film drying, squeegee rollers situated between the wash and drier sections first remove excess water from the emulsion surface. After, the film is transported through the drier section (typical temperature range for automatic processors is 40-65°C) where the film is commonly dried in one of two ways. Two ways a film can be dried Hot air drying Dust-free hot air is blown onto the surface of the film. ii. Infrared drying contains a range of electrically heated elements arranged so as to radiate heat onto both film surfaces as it passes through the heater section. Image Communication The end product of automatic processing is a radiograph. A radiograph can be taken to a radiologist or doctor for viewing and diagnosis. A radiograph can be best viewed with the help of a lightbox. Advantages of Automatic Processing over Manual Processing ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE artefacts in CR and DR CRT04105 · Radiographic Imaging Sciences START READING NOTES Study artefacts in CR and DR using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. Contents of This Topic Artifacts in CR and DR: Definition: Computed Radiography (CR) system X-ray unit Structure of the Imaging Plate Computed radiography Image acquisition Image plate cycle: 1.The cassette is opened in the CR reader with release of the imaging plate from the cassette CR artifacts are broadly classified into 1.Image acquisition artifacts Twin artifact (Double Exposure) Causes Uncollimated images : Delayed Scanning: Abdomen radiographs was also subject to delayed readout. Exposure through the Back of the Cassette This axillary shoulder was exposed through the back of a cassette. Inapropriate exposure factors Inapropriate exposure factor underexposure Underexposure Improper Grid usage: Moire Pattern artefacts in CR and DR Scatter Radiation No erasure of long storage Image plate. Care and Carelessness Light bulb effect 2.Image Processing Artifacts Hardware induced artifacts Thumb radiograph showing cracks (white arrow) that usually first become visible on the IP edges. Artifacts due to dust particles on image plate Disparity artifact Damage of imaging plate due to rollers Dust over rollers : Malfunctioning rollers Plate reader artifact Lateral knee radiograph shows horizontal thin radiopaque line (arrow) overlying supracondylar region. Chest radiograph shows vertical radiopaque line (arrow) cross the right lung region. Cassette related Artifact: Software Induced Artifacts Data cable malfunctioning artifact Artifact due to improper erasure setting This bilateral knee image was spoiled when the incorrect erasure setting was used to eliminate a previous femur image. Artifact of dry Laser Printer Direct Digital Radiography (DDR) 1.Is a cassette-less system Computer processing Noisy Detector Power supply Vertical lines, which are symmetrical around the center of the image, are caused by a noisy detector power supply Tomo Bar Artifact Fibre Optic Cable malfunction Latent Image Loose Cone Bar code artifact Bar artifact References: Artifacts in CR and DR: MODERATOR: PRESENTOR: PRAVEEN KUMAR M Definition: Artifacts are any undesirable objects or structures recorded on the radiograph Computed Radiography (CR) system CR Imaging Plate (IP) -Life is around 10000 exposures -Very sensitive to scattered radiation -The dynamic range is lower than DR -The DQE is lower than DR X-ray unit Image plates CR reader CR workstation Structure of the Imaging Plate There have different layers for different function Protective layer -Insulates IP from handling trauma Phosphor layer -Holds the photostimulable phosphor (PSP) Support layer made of polyester-The base on which the other layers are coated Conductor layer -Grounds the IP eliminating electrostatic problems Light shield layer -Prevents light from erasing data on the IP Computed radiography Image acquisition Image plate cycle: 1.When the exposure is taking, latent image will create in the image plate 2.CR reader will extract the latent image from the image plate 3.After readout the image, the image plate will erase the residual signal by the erasing light. And the plate can reuse again. 1.The cassette is opened in the CR reader with release of the imaging plate from the cassette 2.The image plate is moved by the rollers for scanning by the laser beam 3.The laser light stimulates the trapped electrons to become free and release of light photons 4.The light released from the imaging plate is collected by the fiber-optic light guide and strikes a photomultiplier tube (PMT) where it produces an electronic signal 5.The electronic signal is digitized and stored in a display monitor 6.The image plate is then exposed to a high-intensity halogen lamp which erases any residual energy remaining from a prior exposure 7.The image plate is returned to the cassette which is ready for reuse CR artifacts are broadly classified into 1.Image acquisition artifacts 2.Image processing artifacts 1.Image acquisition artifacts 1.Twin Artifacts (Double Exposure) 2.Uncollimated Images 3.Delayed Scanning 4.Exposure Though the Back of the Cassette 5.Inappropriate Exposure Factors 6.Improper grid usage 7.Scatter Radiation 8.Care and Carelessness 9.Light Bulb Effect Twin artifact (Double Exposure) Postprocedure radiography of KUB with double-J stent shows two double-J stents (arrows) resulting from double exposure, one during inspiration and other during expiration. Repeat radiography taken to reconfirm shows single double-J (arrows) Chest radiography show double exposure due to IP unloading Causes -Two subsequent exposure on same imaging plate Appearance -Duplication of images Remedy -Proper knowledge of using of X-ray equipment Uncollimated images : Uncollimated image resulting from lack of primary beam collimation. Radiograph of pelvis shows increased density over midportion and to right side of pelvis because of improper collimation. Subsequent pelvis radiograph with proper collimation shows uniform density over pelvis. Causes -Improper collimation Appearance -Unsharp images Remedy -Proper collimation in accordance with cassette size and body part Delayed Scanning: Neck radiographs was subject to delayed readout (after 48 hours). It show decreased density in periphery as compared with center of images, as fading of image starts from periphery (arrows) Abdomen radiographs was also subject to delayed readout. It show decreased subject contrast Causes -Delayed between acquisition and processing of image Appearance -Fading of image Remedy -Proper knowledge of radiographers to check that no delay occurs between acquisition and processing. Exposure through the Back of the Cassette Radiograph of neck shows rounded radiopaque ring shadow (arrow) on the right lower part of the neck, which if overlooked, can be wrongly diagnosed as tracheostomy tube This axillary shoulder was exposed through the back of a cassette. A different pattern to the prevision radiography because of different design of the cassette. Causes -Poor basic knowledge of construction of cassettes Appearance -Various patterns of image according to cassette design Remedy -Proper education of radiographers in handling of cassettes Inapropriate exposure factors Overexposure Radiograph of hands shows darkening of image that obscures image details. Artifact is result of overexposure. It occurs over the latitude of the image plate Causes -Improper exposure setting Appearance -Darkening of image Remedy -Proper exposure factors to be used based on body part and patient size Inapropriate exposure factor underexposure Image shows underexposed grainy radiograph

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Chapter 3 Intensifying screen CRT04105 · Radiographic Imaging Sciences START READING NOTES Study Chapter 3 Intensifying screen using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. Chapter 3 Intensifying screen RADIOGRAPHIC IMAGING SCIENCES INTENSIFYING SCREENS An intensifying screen; is a special sheet used to convert xrays into light. When x-rays alone are used to create radiographic images, most pass straight through the films without causing any film blackening (radiographic density). This is because x-rays are so penetrative. Only 1% of x-rays are absorbed by emulsion layers. In order to create adequate film blackening (radiographic density), comparatively large exposures have to be made. This is overcome by the use of an intensifying screen which works to convert small x-ray radiation into large amount of light for image formation. About 30% of the x-rays striking the screen interact with the screen to produce a large number of visible light photons. The use of intensifying screen result in considerable lower radiation dose to the patient but has the disadvantage of causing a slight blurring of the image. Important terminologies Luminescence; refers to the emission of light from a substance bombarded by radiation. Luminescence includes two effects; fluorescence and phosphorescence Fluorescence; refers to the emission of light from a substance bombarded by radiation lasting as soon as radiation exposure is terminated. intensifying screens undergo this phenomena. Phosphorescence; refers to the emission of light from a substance bombarded by radiation which continues for some time (afterglow) even after radiation exposure is terminated. NB; Phosphorescence is an undesirable phenomenon in radiography due to afterglow. Intrinsic/photographic unsharpness; refers to radiographic unsharpness which arises as a consequence of using film and screen material. There are three causes of intrinsic/photographic unsharpness. Divergence of light Poor screen/film contact Cross-over effect Divergence of light; this refers to outward spread of light in all directions from its source. Any point of light arising from the intensifying screen, will no longer be a point by the time it reaches the film emulsion. Poor film/screen contact; loss of close and uniform contact between the screen and film. Cross-over effect; it is the exposure of the emulsion by the light from the opposite intensifying screen. Screen Construction A magnified cross section through an intensifying screen is shown below. (i)Base; is made from paper, cardboard, or more usually a clear plastic such as polyester. Its function is to provide a strong, smooth but flexible support for the fluorescent layer. Thickness of the base is about 0.18mm.Desirable characteristics of base Strong but flexible. Chemically inert/inactive Uniformly radiolucent Moisture resistant Not discolour with age or on exposure to x-rays (ii) Substratum layer; this is the bonding layer between the base and the phosphor layer. It may be reflective, absorptive or simply transparent in nature depending on manufacturer’s intended characteristics for the screen. Reflective substratum layer; it maximizes the effect of the screen by reflecting the light which would be lost through the film, back towards the film emulsion. Absorptive substratum layer; this layer absorbs any light travelling backwards towards the screen base. (iii) Phosphor layer (fluorescent layer); this is the active layer of the screen where fluorescence occurs. It consists of fluorescent crystals (phosphor crystals) which emit light when struck with x-radiation. Phosphor crystals are suspended in a transparent binder such as polyurethane. The binder may also contain carbon granules or acutance dye (coloured pigments) whose function is to absorb any laterally scattered light within the fluorescent layer. →The use of carbon granules minimizes photographic unsharpness but reduces speed of the screen. NB; Coating weight; refers to the quantity of phosphor grains incorporated in a phosphor layer. Factors affecting coating weight; Grain size; it is inversely proportional to coating weight. Coating thickness; it is directly proportional to coating weight. (iv)Supercoat; this is a protective layer and is made up from acetate. It helps to assist surface abrasion. Types of Phosphor Phosphors; are materials which emit visible light when exposed to radiation. Out of many phosphors available, only a few qualify to be used in radiography. The two common qualities of phosphors used in radiography; They are very efficient at x-ray absorption They fluoresce strongly, with little afterglow. There are two main types of phosphors. Conventional phosphors; were common in old screens; e.g. calcium tungstate, barium fluorochloride and barium strontium sulphate. Rare earth phosphors; are common in modern day screens; e.g. gadolinium, lanthanum and yttrium.Advantages of rare earth phosphors over conventional phosphors; They are more efficient at absorbing x-ray photons (absorption efficiency or quantum detection efficiency) They are more efficient at converting x-ray photons to light (conversion efficiency) Quantum Detection Efficiency (QDE) QDE; refers to the ability to absorb incident radiation. Rare earth screens are more efficient in this factor compared to conventional screens of calcium tungstate. Conversion Efficiency This refers to the ability to convert x-ray photon into light. Rare earths are more efficient in this factor as well, e.g. 15- 20% light conversion efficiency compared to calcium tungstate 3-5% Activators Activators; these are small quantities of some foreign materials added to phosphor during manufacture. The phosphor-activator combination determines the intensity of luminescence and colour of light emitted from the screen. Matching film to intensifying screen This involves matching films to the colour of intensifying screen emission. This helps to obtain optimum speed for the film-screen system i.e. maximum film blackening for the least radiographic exposure.e.g. →a screen phosphor emitting light towards the green end of the spectrum is best matched with an orthochromatic film also calcium tungstate (blue emitter) and a monochromatic film. In case of mismatch, the light emission from the screen would have a much diminished effect on the film. Types of screen and their application Screen manufacturers are able to produce a variety of screen speeds by the choice of phosphor and size of the phosphor grain, the addition/exclusion of absorptive/ reflective layers and by varying the amount of reflective/absorptive material used in screen construction. High resolution screen; are

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Chapter 2 Film construction CRT04105 · Radiographic Imaging Sciences START READING NOTES Study Chapter 2 Film construction using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. Chapter 2 Film construction RADIOGRAPHIC IMAGING SCIENCES FILM CONSTRUCTION A film; is a special sheet used to display a radiographic image. There are two main groups of films Direct exposure films (x-ray films) Light only films Direct exposure films; these are films exposed to x-rays alone or to a combination of both x-rays and light. e.g. intra-oral films dental films and radiation monitoring film Light only films; these are films which are sensitive to light only. A film is a made up of several layers as shown below. (i)Film base; made up of cellulose triacetate or polyester. Polyester being the most common. Functions of film base Provides support and stability to emulsion layer Transmits light so that the image can be viewed. Desirable characteristics of film base Transparent and free of any defect Strong but flexible. Uniform in thickness Dimensionally stable throughout processing. Non-flammable. Chemically inactive. Uniform in colour. What is the thickness of film base? Thickness of film base depends on type of film and its use. Medical x-ray film needs a film base of 0.18mm.(ii)Subbing/adhesive layer; it is situated between the base and emulsion layer. Functions It ensures that the emulsion layer adheres to the base material. To prevent any separation of the emulsion from the base during processing. (iii)The emulsion layer; it is the layer in which a radiographic image is formed. It consists of photosensitive materials suspended in gelatin. Types of films according to film construction Duplitized films; these are films with an emulsion layer on both sides of the base. Single sided film; these are films with one emulsion layer only on one surface of the base.(iv)The supercoat; this is a thin layer of clear gelatin. Functions To protect the sensitive emulsion. To provide suitable surface characteristics. (iv)Non-curl backing; this is a layer which prevents curling in single-sided emulsion films. Since emulsion layer usually swells during processing, it gives single-sided emulsion films a tendency to curl.→ Duplitized films have no tendency to curl due to presence of emulsion layer on each side of the film base hence they have no non-curl backing layer. (iii)Anti-halation layer; it is the layer which prevents reflection of light from the film base back to the emulsion. When light is reflected from the film base back to the emulsion it causes halation. Halation refers to production of diffuse image or ‘halo’ around a proper image.Manufacturers use the following methods of preventing halation. Adding a dye to the non-curl backing. Adding a dye to the base. NB; → Crossover effect; is the type of halation which occurs when a film is used with intensifying screen. Irradiation; is the sideways scattering of light within the emulsion itself. Just like halation, irradiation is another source of image unsharpness.Light-sensitive and X-ray sensitive emulsions There are two fundamentally different conditions of exposure for the films used in an x-ray department. They may be exposed to visible light emitted by fluorescent intensifying screen. They may be exposed solely to radiation. Light-sensitive film Light sensitive films are films in which production of an image is through exposure to visible light.NB; All films are light sensitive but this group of films refers to those films whose image has been formed after exposure to light. The emulsion layer of the film must absorb the energy of the visible light photons incident on it in order to form an image. Silver halide grains in the emulsion layer do absorb visible light photons particularly light in the blue-violet part of the spectrum. But for a photon to be absorbed, there must be a silver halide grain in its path. Therefore, to ensure efficient absorption, the emulsion must contain high concentration of silver halide. The following are ways to increase concentration of silver halide in order to ensure efficient absorption of light photons. Close parking of the silver halide grains Increasing the size of the silver halide grains Increasing the thickness of the emulsion layer Modifying the shape of the halide grains However, emulsion thickness must be limited to optimum thickness for several reasons; Image resolution tends to reduce as emulsion thickness increases. Thick emulsion layers require longer processing times. Most absorption of light occurs in the upper layers of the emulsion. Duplitized films Duplitizing of film is a method of gaining the benefits of increased emulsion thickness with few of the drawbacks. Duplitized film is designed to be used with two intensifying screens. It is the most commonly used type of x-ray film in a radiology department. After processing, a duplitized film has two identical images, one on each side of the film base. When a radiograph is viewed, the two images are superimposed and observed as one. Only on a very close observation it is possible to detect the dual imaged due to parallax effect.Advantages of duplitized films Increased sensitivity; adequate image density can be achieved from a smaller radiation exposure. Increased image contrast; contrast is the ability to distinguish between two different densities on the image. Disadvantages of duplitized films Loss of image quality; due to incidences like crossover effect. Economic reasons; they require a high coating weight of silver than single emulsion films. Silver is an expensive resource. ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Chapter 1 Intro to Imaging Sciences CRT04105 · Radiographic Imaging Sciences START READING NOTES Study Chapter 1 Intro to Imaging Sciences using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. Chapter 1 Intro to Imaging Sciences RADIOGRAPHIC IMAGING SCIENCES Introduction to Radiographic and Imaging Sciences What is an image? An image is a recognizable pattern carrying useful information. An images can be; Real images; those having a real, physical existence e.g. photographic and radiographic images (x-ray images). Mental image; those generated as mental pictures. Production of an x-ray image Production of a radiograph (x-ray image on a film) involves three stages; The formation of an invisible x-ray image (latent image) The conversion of the invisible x-ray image into a visible light image. ‒ This is done through chemical processing of the film. The viewing, perception and interpretation of the visible image. ‒ This is done by the aid of a lightbox. How is an image recorded on a film? The traditional way in which x-rays images are recorded is by using photographic effect of X-radiation on sensitive emulsion.What is photographic effect? Photographic effect refers to the structural changes of some chemical compounds when they are exposed to electromagnetic radiation. The electromagnetic radiation can be visible light, ultraviolet light or x-rays. These chemical changes are usually invisible but they are made visible through chemical processing. NB; Photographic development; is the chemical processing necessary to make the invisible changes visible on a photosensitive material.What is a photosensitive material? Photosensitive material refers to any material which undergoes chemical changes when exposed to electromagnetic radiation. The photosensitive materials used in radiography are known as silver halides. Silver Halides The silver halides are a group of chemical compounds consisting of atoms of the element silver combined with atoms of the halogen elements; bromine, iodine and chlorine. The compounds thus formed are silver bromide, silver iodide and silver chloride respectively. These compounds are used because they are sensitive to light and x-rays. When they are exposed to radiations they undergo changes which enable them to form a photographic or radiographic image. Physical properties of silver halides They are white or pale yellow crystalline salts similar in appearance to common salt. The links between silver and halogen atoms are ionic bonds. NB; Ionic bonds occur when positive (+) and negative (-) ions are locked together by electric forces. In silver halides, the silver ions are positively charged (+) and the halide ions are negatively charged (-).The electric forces fix the positions of silver and halide ions in a regular three dimensional crystal structure or lattice.Chemical properties of silver halides Pure silver halide crystals are chemically stable and do not easily suffer chemical breakdown. Under certain conditions, it is possible to neutralize all the positively charged silver ions in a crystal and convert them to atoms of metallic silver. This conversion is achieved by donating –vely charged electrons to the silver ions. A chemical which provide a supply electrons for this purpose is called a reducing agent. NB; A reducing agent; is a chemical which provides a supply of electrons in order to reduce silver halide to metallic silver. The chemical reduction of a silver halide sample which has been exposed to radiation takes place much more rapidly (because of weakened bonds) than the reduction of an unexposed sample.NB; In photographic development, what actually takes place is chemical reduction of silver halide to metallic silver. ⸫ Photographic development is primarily a process of chemical reduction. What happens when a silver halide is irradiated? Invisible structural changes occur in silver halide crystals when exposed to radiation. The following image shows a regular arrangement of silver and bromine ions in a crystal. What is a sensitivity speck? A sensitivity speck refers to a low energy electron trap in a silver halide crystal. It is where electrons collect after exposing the halide crystal to radiation. NB; Sensitivity specks are formed by deliberate introduction of ‘impurities’ into the crystal during its manufacture. What is a latent image? A latent image is an invisible image formed on a film after exposure to radiation. A latent image is later made visible through photographic development. In a latent image, very few exposed silver halide crystals have been completely reduced to metallic silver. To complete the process, photographic development is required. Only after completing this process can the image become visible. Differences between silver halides and metallic silver NB; the conversion from silver halide to metallic silver in exposed part is important because the two substances have different properties; Silver halides are sensitive to light while metallic silver is not. Metallic silver is opaque to light and is seen as a darkened area. The blackened parts of a radiographic image are due to metallic silver. Silver halides can be converted into soluble compounds by the action of chemicals known as fixing agents. NB; an image which contains silver halide can undergo changes whenever exposed hence it cannot be a permanent image. An image formed only by metallic silver cannot undergo any changes even when exposed again hence it is a permanent image. Light sensitive and X-ray sensitive films Light sensitive films are films in which production of an image is through exposure to visible light. X-ray sensitive films are films in which production of an image is through exposure to x-rays. NEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES