CRT04105 Radiographic Imaging Sciences

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Processing Chemicals CRT04105 · Radiographic Imaging Sciences START READING NOTES Study Processing Chemicals using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. Contents of This Topic PROCESSING CHEMICALS LATENT IMAGE LATENT IMAGE CONT. LATENT IMAGE FORMATION LATENT IMAGE FORMATION cont. Its primary purpose is convert latent image into visible image CHEMICAL ACTION OF DEVELOPER Chemical Action of Developer cont.. EFFECTS OF THE BY-PRODUCTS OF DEVELOPMENT CONSTITUTION OF DEVELOPER SOLUTION CONSTITUENTS OF DEVELOPER REPLENISHER SOLUTION SOLVENT – WATER DEVELOPING AGENTS DEVELOPING AGENTS Cont .. ADVANTAGES OF PQ DEVELOPER Advantages of PQ Developer cont… The shape of the characteristic curve is controlled by the two developing agents developer…. ACCELERATORS developer…. Accelerators cont… developer…. BUFFERS developer…. RESTRAINERS PRESERVATIVES SEQUESTERING AGENTS STARTER SOLUTION EFFICIENCY OF DEVELOPMENT & FACTORS AFFECTING DEVELOPMENT HOW CONSTITUTION OF THE DEVELOPER AFFECT DEVELOPMENT? HOW DOES DEVELOPER TEMPERATURE AFFECT DEVELOPMENT? EFFECT OF INCREASE OF TEMPERATURE EFFECT OF DECREASE OF TEMPERATURE DEVELOPER TEMPERATURE IN MANUAL PROCESSING DEVELOPMENT TIME DEVELOPMENT TIME IS DETERMINED BY: Development is the most important part of processing KEY POINTS FIXING (FIXATION) Fixing (fixation), cont… CONSTITUENTS OF FIXING SOLUTION Constituents of Fixing Solution cont… Constituents of Fixing Solution, Chemical reaction cont… Constituents of Fixing Solution cont…ACID Constituents of Fixing Solution cont…HARDENER Constituents of Fixing Solution, Hardener cont… Constituents of Fixing Solution, BUFFER Constituents of Fixing Solution, PRESERVATIVE Constituents of Fixing Solution, ANTI-SLUDGING AGENT Fixing, cont… FACTORS AFFECTING FIXATION Fixing, cont… FACTORS INFLUENCING QUANTITY & QUALITY OF FIXING Fixing…Factors Influencing Quantity & Quality of Fixing: 1.FIXER CONSTITUTION Fixing… Factors Influencing Quantity & Quality of Fixing…1.Constitution cont… Fixing… Factors Influencing Quantity & Quality of Fixing…2. FIXER TEMPERATURE Fixing… Factors Influencing Quantity & Quality of Fixing…3. FIXING TIME Fixing… Factors Influencing Quantity & Quality of Fixing…3. Fixing Time cont… Fixing… Factors Influencing Quantity & Quality of Fixing…3. Fixing Time , Determining Factors cont… Fixing… MAINTENANCE OF FIXER VOLUME Fixing… FACTORS AFFECTING FIXER REPLENISHMENT RATE RINSING, WASHING & DRYING RINSING, WASHING & DRYING: 1. RINSING Rinsing, Washing & Drying: Rinsing cont… Rinsing, Washing & Drying: 2. WASHING Rinsing, Washing & Drying: 2. Washing: FACTORS AFFECTING WASHING EFFICIENCY Rinsing, Washing & Drying: 3. DRYING Rinsing, Washing & Drying: 3. Drying, cont… Rinsing, Washing & Drying: 3. Drying, FACTORS ON DRYING TIME Rinsing, Washing & Drying: 3. Drying… Factors on Drying Time cont… PROCESSING STAGES MANUAL FILM PROCESSING Manual Film Processing, cont…. Manual Film Processing…THE CYCLE Manual Film Processing…The Cycle cont… Manual Film Processing…STOP BATH/RINSING Manual Film Processing…Rinsing/Stop Bath, cont… Manual Film Processing…REPLENISHMENT PROCESSING CHEMICALS PROCESSING CHEMICALS The primary purpose of a radiographic processing is to deposit enough black metallic silver at the latent image sites to permit a permanent visible image to form The development of latent image can be accomplished manually or with automatic processing equipment.The development and fixing are accomplished in a solution of numerous chemicals LATENT IMAGE The silver bromide crystals consist of positive silver and negative ions arranged in geometrical pattern known as a crystal lattice When silver bromide grain is exposed to light or x-ray some of the bromide ions in the lattice emit electrons Electrons are trapped in the electron- trap in the crystal An electron trap is a region of low energy called a sensitivity speck producing during manufacture Electrons tend to collect at sensitivity speck and they confer on speck a negative charge A crystal lattice LATENT IMAGE CONT. Silver ions in the crystal have a positive charge, the silver which are free to move are attracted to the negative charge electrons in a sensitivity speck The negative charge on the electrons neutralises the positive charge on the silver ions; hence forming silver atoms LATENT IMAGE FORMATION How the film works Latent: Hidden – as the silver halide crystals are exposed to electromagnetic radiation, they are ionized and conversion to metallic silver is begun. This is completed in the processor LATENT IMAGE CONT. HOW THE FILM WORKS CONT. Sensitization speck Impurities/imperfections intentionally introduced to crystals during manufacturing. Found on surface of crystal Acts as electron trap, trapping electrons released during ionization of crystals. Essential for development of black metallic silver LATENT IMAGE FORMATION The latent image is theorized as being formed in the following manner: Radiant energy (x-ray photon or light photon from screen) strike the crystal & liberates an electron from the valence shell of a bromide ion. This electron is then free to move about in the crystal. If it strikes a sensitivity speck, it may be trapped giving the speck a negative charge. When a positive silver ion comes within the negative field of the speck, it may be attracted to the speck & take on an electron thus forming an atom of metallic silver LATENT IMAGE FORMATION cont. Occurs many times within the same crystal when struck by radiant energy. Once the film has been exposed to radiant energy & a latent image has been formed, the film is capable of developing a radiographic image. Chemicals in the processor greatly enhance this chemical reaction converting a latent image to a visible image LATENT IMAGE FORMATION cont. IN SUMMARY Electrons (released by light from bromine ions) are trapped Positive silver ions are trapped at the sensitivity speck by the negative charges on the electrons Positive charges on the silver ions are neutralized by negative charges on the electrons and silver atoms form Processing Chemicals Film Processing is a predetermined sequence of chemical treatment of the exposed film whereby the latent image is transformed into a visible image in a dry film. CHEMICALS IN AUTOMATIC PROCESSOR Four stages in Automatic processing namely Development, Fixing, Washing and Drying Developing:- it is the first step in processing film, at this stage silver is deposited at the latent image site and an image becomes visible. Processing Chemicals The deposition of silver amplifies the density of the image, a modern x-ray developers are capable of amplifying the image by a factor of 108 to 10 9 within 3-4 mins . Its primary purpose

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Radiographic Imaging Science CRT04105 · Radiographic Imaging Sciences START READING NOTES Study Radiographic Imaging Science using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. Contents of This Topic DUPLITEZED FILM Advantages of duplitized fil Radiographic Imaging Science Disadvantage Photographic characteristics of x ray film Photographic density Radiographic Density Factors affecting density Contrast Film contrast Film contrast depends on four Characteristics curve Film density is plotted on the vertical axis and Film latitude Cross over exposure Spatial resolution Noise Density is expressed as a number that is actually a logarithm, using the common base 10. Refer to Figure 11-1. If ten arrows (photons) Higher density means a blacker film (less Typical characteristic curve of a Cross over exponsure The ideal way to reduce print-through RADIOGRAPHIC IMAGING SCIENCE DUPLITEZED FILM The duplitizing of film is a method of gaining the benefits of increased emulsion thickness with few of the drawbacks. Duplitized film is designed for use with two intensifying screens and is still the most commonly used type of X-ray film in the X-ray department. Advantages of duplitized fil (1) Increased sensitivity, i.e. adequate image density can be achie\'ed from a smaller radiation exposure. This has two important consequences: (a) Radiation doses to patients and staff are reduced; (b) Wear on the X-ray tubes is reduced, thus extending their working life. Radiographic Imaging Science Increased image contrast: the contribution made by film emulsion to the eventual contrast of the image is greater because of the greater effective emulsion thickness. Disadvantage (1) Loss of image quality: the use of a duplitized film and twin-screen system may introduce a loss of image quality compared with other image recording systems. For example, the crossover of light from each intensifying screen to the emulsion on the 'wrong' side of the film leads to a loss of sharpness in the image. Radiographic Imaging Science (2) Economic reasons: duplitized films use a higher coating weight of silver than single-coated films, and silver is an expensive and diminishing world resource. Photographic characteristics of x ray film Exposure is proportional to the product of the milliamperes of x-ray tube current and the exposure time. Thus, an exposure of 100 milliamperes for 1 second is expressed as 100 milliampere-seconds, usually written 100 mAs. Radiographic Imaging Science Exposure (mAs) of the x-ray film produces film blackening, or density. The quality of the x-ray beam (kVp) has more effect on image contrast. mAs controls film density kVp controls image contrast Photographic density When the x-ray beam passes through body tissues, variable fractions of the beam will be absorbed, depending on the composition and thickness of the tissues and on the quality (kVp) of the beam. defines an image as "a mental representation of anything not actually present to the senses." Radiographic Density Density is the amount of the overall blackness produced on the image after processing A radiograph that is too light has insufficient density to visualize anatomic structures while if its too dark, has excessive density and anatomic parts can not be visualized. Factors affecting density X-ray Absorption: Dense structures like bones absorb more X-rays, resulting in brighter areas on the image. In contrast, softer tissues absorb fewer X-rays and appear darker. Exposure Settings: The amount of radiation exposure (controlled by mAs – milliampere-seconds) directly affects image density. Higher mAs produces darker images, while lower mAs produces lighter images. Radiographic Imaging Science the degree of film blackening is directly related to the intensity of radiation reaching the film or intensifying screen. The measurement of film blackness is called "photographic density“ Radiographic Imaging Science Higher density means a blacker film (less light transmission). In routine x-ray work, a density of 2 (1% of light transmitted) is black when viewed on a standard view box, and a density of 0.25 to 0.3 (50% of light transmitted) is very light. Radiographic Imaging Science The important part of them characteristic curve is between the toe and shoulder, and in this region the curve is almost a straight line. In this "straight line“ portion the density is approximately proportional to the log relative exposure. Contrast Contrast is the degree of difference between adjacent densities. It is the photographic density difference between two adjacent areas on a film/image The ability to distinguish between densities enables differences in anatomical tissues to be visualized. Contrast can be evaluated best when the radiographic density is adequate to visualize density differences Radiographic Imaging Science Radiographic contrast depends on subject contrast and on film contrast. Subject contrast depends on the differential attenuation of the x-ray beam as it passes through the patient. Subject contrast was seen to be affected by the thickness, density, and atomic differences of the subject, the radiation energy (k V p ), contrast material, and scatter radiation. Radiographic Imaging Science The radiographer is required to understand the anatomic structure to be radiographed for him/her to determine the factors required to achieve desired level of radiographic contrast. Factors affecting contrast; Kilovoltage Grids Collimation Object to Image receptor distance Anatomic part Contrast media Processing Film contrast Radiographic contrast is the density difference between image areas in the radiograph. There are many definitions of contrast, but we will use the simple definition that contrast is the difference in density existing between various regions on the film. Film contrast depends on four factors: characteristic curve of the film film density screen or direct x-ray exposure film processing Characteristics curve Is the relationship between the exposure a film receives and the density produced by the exposure. Radiographic Imaging Science The relationship between exposure and density is plotted as a curve, known as the "characteristic curve" or "H and D curve" (named after F. Hurter and V.C. Driffield, who first published such a curve in England in 1890). The concept of the characteristic curve of an x-ray film exposed by light from x-ray intensifying screens is illustrated in Figure 11-4. Film density is plotted on the vertical axis and film

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Radiographic Imaging Sciences CRT04105 · Radiographic Imaging Sciences START READING NOTES Study Radiographic Imaging Sciences using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. Contents of This Topic Image formation and characteristics FILM CONSTRUCTION Base: A polyester material that provides support.- Radiographic Imaging Sciences When x-rays gamma rays, or light strike the grains Exposure to X-rays Interaction with Silver Halide Crystals Sensitivity Speck and Electron Capture Formation of Metallic Silver Invisible Until Developed Film storage and handling • Skin gets dry and brittle in low humidity and cold; so does film. Keeping your raw stock and exposed film safe Exposed Unprocessed: Use of envelope-packed films avoids many of these problems until the envelope is opened for processing. RADIOGRAPHIC IMAGING SCIENCES Image formation and characteristics Film construction Types of Film Latent image formation The duplication film process Film storage and handling Film identification X-ray Cassettes FILM CONSTRUCTION X-ray films for general radiography consist of an emulsion-gelatin containing radiation sensitive silver halide crystals, such as silver bromide or silver chloride, and a flexible, transparent, blue-tinted base. The emulsion is different from those used in other types of photography films to account for the distinct characteristics of gamma rays and x-rays but X-ray films are sensitive to light. Usually, the emulsion is coated on both sides of the base in layers about 0.0005 inch thick Duplitized film Single sided – film Base: A polyester material that provides support.- Adhesive Layer/Subbing layer : Binds the emulsion to the base.- Emulsion Layer: Contains silver halide crystals suspended in gelatin; this is where the image is formed.- Protective Layer: A thin coating to protect the emulsion from physical damage Radiographic Imaging Sciences Putting emulsion on both sides of the base doubles the amount of radiation-sensitive silver halide, and thus increases the film speed .The emulsion layers are thin enough so developing, fixing, and drying can be accomplished in a reasonable time. A few of the films used for radiography only have emulsion on one side which produces the greatest detail in the image. When x-rays gamma rays, or light strike the grains of the sensitive silver halide in the emulsion, some of the Br- ions are liberated and captured by the Ag+ ions. This change is of such a small nature that it cannot be detected by ordinary physical methods and is called a "latent (hidden) image Radiographic Imaging Sciences " However, the exposed grains are now more sensitive to the reduction process when exposed to a chemical solution (developer), and the reaction results in the formation of black, metallic silver. It is this silver, suspended in the gelatin on both sides of the base, that creates an image. Exposure to X-rays When the X-ray beam passes through the patient, it reaches the intensifying screen.- The screen converts X-rays into visible light (or sometimes direct X-rays hit the film in non-screen systems). Interaction with Silver Halide Crystals Interaction with Silver Halide Crystals:- The light (or X-rays) interacts with silver halide crystals (mainly silver bromide) in the emulsion layer of the film.- The energy from this interaction excites electrons within the crystals Sensitivity Speck and Electron Capture The free electron migrates to a sensitivity speck (a defect or impurity in the crystal) The speck becomes negatively charged and attracts positive silver ions (Ag⁺) Formation of Metallic Silver The silver ions gain electrons and are reduced to metallic silver (Ag).- This forms a small cluster of metallic silver atoms at the sensitivity speck — this is the latent image center. Invisible Until Developed These tiny metallic silver clusters are not yet visible.- During chemical processing, they are amplified to form a visible (manifest) image Film storage and handling Film seems to be derived from an old word for skin. Skin and film can be mistreated in similar ways: Skin can be scratched; so can film. Skin can be blistered by chemicals or heat; so can film. Skin can be damaged by prolonged exposure to the sun; so can film. • Skin gets dry and brittle in low humidity and cold; so does film. Skin is susceptible to fungus in excessive heat and relative humidity; so is film. Skin can be burned; so can film. Keeping your raw stock and exposed film safe Unprocessed film must be kept cool to preserve quality, ideally at 55°F / 13°C Keep film cool until just before shooting For storage of film for longer than 6 months, store at 0°F / -18°C Allow frozen film to warm up gradually before opening can, to avoid condensation Avoid prolonged exposure of film cans or camera magazines to sunlight Avoid storing film in hot vehicles Exposed Unprocessed: Process film promptly after exposure Avoid “Latent Image Regression” Keep film cool after exposure If processing is delayed, put film in refrigerator Allow frozen film to warm up gradually before opening can for processing Film storage and handling X-ray film should always be handled carefully to avoid physical strains, such as pressure, creasing, buckling, friction, etc Marks resulting from contact with fingers that are moist or contaminated with processing chemicals, as well as crimp marks, are avoided if large films are always grasped by the edges and allowed to hang free Use of envelope-packed films avoids many of these problems until the envelope is opened for processing. Another important precaution is to avoid drawing film rapidly from cartons, exposure holders, or cassettes. Such care will help to eliminate circular or treelike black markings in the radiograph that sometimes result due to static electric discharges. Film fog ← 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 X-ray imaging teacher notes CRT04105 · Radiographic Imaging Sciences START READING NOTES Study X-ray imaging teacher notes using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. X-ray imaging teacher notes Copyright Institute of Physics 2012 Page 1 Teaching Medical Physics X-ray imaging Curriculum links Electromagnetic spectrum Background radiation Introduction X-ray imaging utilises the ability of high frequency electromagnetic waves to pass through soft parts of the human body largely unimpeded. For medical applications, X-rays are usually generated in vacuum tubes by bombarding a metal target with high-speed electrons and images produced by passing the resulting radiation through the patient’s body on to a photographic plate or digital recorder to produce a radiograph, or by rotating both source and detector around the patient’s body to produce a “slice” image by computerised tomography (CT). Although CT scans expose the patient to higher doses of ionising radiation the slice images produced make it possible to see the structures of the body in 3D. Lesson notes Radiography In X-ray radiography images are produced by casting an Xray shadow onto a photographic film or digital detector: Like gamma rays, X-rays can travel through soft tissues in body with little attenuation and are only “stopped” by high density tissues such as bone. Radiograph: Fully exposed areas of film/detector appear black. Dense objects block more X-rays and so appear white. Soft tissues like fat and muscle result in intermediate exposure and so appear grey. X-rays In the high- frequency/short-wavelength part of the electromagnetic spectrum the distinction between X-rays and gamma-rays is made by the origin of the waves: X-rays are emitted (by definition) by electrons outside the nucleus, while gamma rays are emitted by the nucleus. For most medical application X-rays are produced using evacuated tubes in which the electrons are accelerated up to high speed using large voltages. The X-rays are produced when the electrons hits a metal target.Copyright Institute of Physics 2012 Page 2 Teaching Medical Physics X-ray imaging Computerised tomography (CT) X-ray source and detector rotated around body as patient moves through scanner The data collected can be processed using a computer to produce a slice or 3D image. Compared to radiography, CT imaging better for: imaging of soft tissues differentiating between overlying structures in the body. PLAY: Scan of person moving through scanner (head to legs). Lungs and other major organs can be seen. X-ray dose CT scans require exposing the patient to higher dose of ionising radiation than radiographs which increases patient risk of cancer. Consequently, the additional risk associated with a CT scan must be weighed up against benefits of enhanced diagnostic capabilities (e.g. the ability to manipulate the data to produce 3D simulations) Exposure is measured in milliSievert (mSv) and is often expressed in equivalent background-radiation exposure time. Over a lifetime, medical X-rays contribute approximately 20 % of background level for the average person in UK. Chapter 3: launch chapter 3 of schools lecture 2011 on X-rays. Chapter 5: launch chapter 5 of schools lecture 2011 on CT scanning.Copyright Institute of Physics 2012 Page 3 Teaching Medical Physics X-ray imaging Worksheet Mark scheme 1. black; white Any one from: Images can be produced and checked immediately; OR There is no need for a developing film and disposing of expensive chemicals; OR Image can be manipulated to get the clearest possible picture; OR Image can be stored easily. 2. X-rays can pass through (soft tissues in) the body/have different frequency (high-speed) electrons (hit) metal target ultraviolet/UV [accept gamma-rays] 3. (X-rays cause) ionisation/changes in cells/damage DNA/ cancer. (CT scans) better at mapping soft tissues/ differentiating between overlying structures in the body/making 3D images Radon gas/ground/food/drink/cosmic rays Calculation of daily or annual background count rate: 0.0057 (mSv/day) or 2.1 (mSv/year) Answer: 246 days/0.67 years Total 10 marks ← PREVIOUS TOPICVIEW 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 CRT04105 Radiographic Imaging Sciences Notes Browse 14 study topics in Radiographic Imaging Sciences, NTA Level 4, Semester 1. Chapter 1 Intro to Imaging Sciences Chapter 2 Film construction Chapter 3 Intensifying screen artefacts in CR and DR Automatic Processing Developer V Fixer Film Processing Image Artifacts – Imaging Imaging Process Imaging Science Session Processing Chemicals Radiographic Imaging Science Radiographic Imaging Sciences X-ray imaging teacher notes ← PREVIOUS MODULENEXT MODULE →SEMESTER NOTESNTA LEVEL 4 NOTESALL 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