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Introduction to Image Recording

Introduction to Image Recording. Lecture (2). Learning Objectives. By the end of this Lecture the student will be able to:. Explain how to produce x-rays and discuss its properties List the basic components of the radiographic machine and identify primary functions of each.

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Introduction to Image Recording

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  1. Introduction to Image Recording Lecture (2)

  2. Learning Objectives By the end of this Lecture the student will be able to: Explain how to produce x-rays and discuss its properties List the basic components of the radiographic machine and identify primary functions of each. Explain the exposure factors and the effect of each factor on image formation Understand the basic concept of recording the radiographic image on the image receptor List the Basics steps of image processing procedures

  3. References • S.C.Kapur, Basics in Medical Radiographic Imaging; King Fahad national Library,2004 • Useful Websites • http://www.e-radiography.net/

  4. Equipment Needed Image Recording • To produce x rays • To record the image • To control size & shape of beam • Accessories & patient comfort items • To process the image

  5. X-Ray Producing Equipment • x-ray tube • high voltage generator • control console

  6. X-Ray Tube Glass vacuum diode tube • cathode • negative electrode • source of electrons • 2 filaments (coils) cathode - anode + • anode • positive electrode • attracts & stops electrons

  7. X-ray Tube anode cathode

  8. High Electrical Potential Electrons + - Radiation Penetrate the Sample Exposure Recording Device What Happens in an X-Ray Tube: • Cathodesupplies e- • anodeattracts e- • Electronsmove at high speed (KE) to target • Collide with target • KE of e- changed to x rays & heat

  9. - + High Voltage Generator • Provides power to move (accelerate) electrons from cathode to anode • 40,000 to 150,000 volts (40 TO 150 KVp) 1,000 volts = 1 KVp V to kV  1000 kV to V 1000 • Connected to x-ray tube with high tension cables - + HV generator

  10. CONTROL CONSOLE or PANEL • MAIN ELEMENTS • main power switch (circuit breaker near console) • ON/OFF (on the console) • Technique controls (kV, mA, t, etc.) • Exposure controls • Equipment operation indicators

  11. KVp SELECTION • KVp used to control ENERGY LEVEL of x rays • PENETRATION (QUALITY)OF BEAM • main control for image CONTRAST • selection in unit value range from ~40 KVp to 150 KVp • Increments: major = 10 KVp minor = 1 KVp

  12. mA SELECTION • MILLIAMPERAGE 1A =1000 mA [A 1000 = mA] 1mA =0.001 A [mA 1000 = A] • Amperage # of e- flowing in a current • Controls # of x rays produced • QUANTITY OF X RAYS IN BEAM • Main control for image DENSITY

  13. TIME SELECTION • length of time machine produces x rays • range of selections usually at specific values • not same all machines

  14. mA & Time work together combined for total control on QUANTITY • mA = # of e- (per second of time) • time = duration Relative value for total # of x rays • mAs = mA X t • when émAs = similar éin # of x rays • 2x mAs = 2x # of x rays

  15. what is the mAs for 300 ma at 6 ms? mAs = mA x T T = 6 1000 = .006 s = 300mA x .006 s = 1.8 mAs

  16. IMAGE PRODUCTION EQUIPMENT • FILM -- SPEED • SLOW = éX RAYS & éDETAIL • FAST = êX RAYS & êDETAIL • numerical values indicating relative change in radiation needed (inverse relationship) 100200 300 400 -- SIZES 8X10, 10X12, 7X17, 14X17, . . . -- TYPES single vs. double emulsion

  17. CASSETTES • light tight holders for film • sized for film • FRONT vs. BACK • ID window • Types • cardboard vs. screen

  18. Film Processing • Exposed film must be processed • makes the image visible • makes the image permanent • Automated machines • “stand by” mode • replenishment inside darkroom outside darkroom feed 1-developer receiving 1 2 3 4 bin 2-fixer 3-wash 4-dry

  19. Properties of X Rays (1) Penetration • Able to pass through matter in varying degrees • METALS = MOST DIFFICULT • BONE = EASIER THAN METAL • MUSCLE = EASIER THAN BONE • AIR = EASIEST

  20. Properties (2) Photographic Effect • similar to light • exposes film by darkening it • many x rays = black • fewer x rays = gray • no x rays = white (clear) • examples: • AIR = BLACK • MUSCLE = DARKGRAY • BONE = LIGHT GRAY • METALS = WHITE

  21. e- ion pair ionized atom 11e- 12p+ Properties (3) Properties (4) Fluorescent Effect • causes certain materials to emit light original atom 12e- 12p+ X ray Ionization • able to free electrons from orbiting around the nucleus of an atom • energy of x ray used to "free" the electron • ionpair= ionized atom and freed e-

  22. Properties (5) Biologic effects • harmful effects caused by the ionization of atoms in living organisms • Examples • Cellular damage • Tissue damage (radiation burns, etc.) • Organ damage

  23. Radiography • PROCESS • Machine produced X RAYS are directed toward & through an object • X RAYS TRAVEL IN STRAIGHT LINES • INTERACT WITH OBJECT 1. PASS THROUGH UNAFFECTED 2. ARE ABSORBED BY STRUCTURES IN OBJECT 3. ARE SCATTERED BY THE OBJECT (CHANGE DIRECTION & LOSE ENERGY)

  24. Transmit vs.Absorb vs.Scatter

  25. Recording of the Image • Medical images are recorded either in • digital format on some form of digital media • or on photographic film. • The process of recording images on film.  • The active component of film is an emulsion of • radiation-sensitive crystals coated onto a transparent • base material. • The production of an image requires two steps. First, • the film is exposed to radiation, typically light, • which activates the emulsion material but produces • no visible change. • The exposure creates a so-called latent image. • Second, the exposed film is processed in a series • of chemical solutions that convert the invisible • latent image into an image that is visible as different • optical densities or shades of gray.

  26. Recording of the Image • Image receptor (sensors or film) records X RAYS that penetrate object & reach film • image based on the differences between the transmitted & absorbed x rays • image is processed to make it visible • Sensors – digital processing • Film – chemical processing

  27. Film Processing • Exposed film must be processed • makes the image visible • makes the image permanent • Automated machines inside darkroom outside darkroom feed 1-developer receiving 1 2 3 4 bin 2-fixer 3-wash 4-dry

  28. Radiograph • FILM = BLACK-GRAY-WHITE IMAGE OF THE OBJECT • scatter has a negative impact, causing • film fog (overall graying effect) • greatest cause of occupational exposure

  29. Digital Radiography • Emerging imaging method that uses • sensors used to digitize image information • computer storage and manipulation of the image rather than film processing • Images viewed on monitor or printed on film with a laser printer • PACS - Picture Archiving & Communication System • Computer network designed to connect imaging components throughout department and hospital also saves images produced or converted to a digital format

  30. IP reader & data entry workstation post-processing workstation laser printer digital archive • Digital Radiography • Image data captured on an imaging plate (IP) • IP read to produce a digital image • Patient data merged to digital image • Post-processing adjustments to image • Image sent to • Laser printer (hard copy) • Viewing station (PACS) • Digital archive (PACS)

  31. Thank you

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