Lecture (2)

2 1.Explain how to produce x-rays and discuss its properties 2.List the basic components of the radiographic machine and identify primary functions of each. 3.Explain the exposure factors and the effect of each factor on image formation 4.Understand the basic concept of recording the radiographic image on the image receptor 5.List the Basics steps of image processing procedures Learning Objectives By the end of this Lecture the student will be able to:

3 References S.C.Kapur, Basics in Medical Radiographic Imaging; King Fahad national Library,2004 Useful Websites

 To produce x rays  To record the image  To control size & shape of beam  Accessories & patient comfort items  To process the image 4

 x-ray tube  high voltage generator  control console 5

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

7 anodecathode X-ray Tube

 Cathode supplies e-  anode attracts e-  Electrons move at high speed (KE) to target Collide with target KE of e- changed to x rays & heat 8 High Electrical Potential Electrons - + Exposure Recording Device Radiation Penetrate the Sample

 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 9 HV generator

MAIN ELEMENTS 1. main power switch (circuit breaker near console) 2. ON/OFF (on the console) 3. Technique controls (kV, mA, t, etc.) 4. Exposure controls 5. Equipment operation indicators 10

 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 11major minor

 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

length of time machine produces x rays range of selections usually at specific values not same all machines

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  mAs = similar  in # of x rays  2x mAs = 2x # of x rays 14

mAs= mAx T T = 6  1000 =.006 s =300mA x.006 s =1.8 mAs 15

16 1 FILM -- SPEED  SLOW =  X RAYS &  DETAIL  FAST =  X RAYS &  DETAIL  numerical values indicating relative change in radiation needed (inverse relationship) SIZES8X10, 10X12, 7X17, 14X17, TYPESsingle vs. double emulsion

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

18  Exposed film must be processed  makes the image visible  makes the image permanent  Automated machines  “stand by” mode  replenishment inside darkroom 1234 feed receiving 1-developer 2-fixer 3-wash 4-dry bin outside darkroom

Penetration Able to pass through matter in varying degrees METALS=MOST DIFFICULT BONE=EASIER THAN METAL MUSCLE=EASIER THAN BONE AIR=EASIEST 19

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

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

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

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) 23

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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.

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 26 Recording of the Image

Exposed film must be processed makes the image visible makes the image permanent Automated machines 27 inside darkroom 1234 feed receiving 1-developer 2-fixer 3-wash 4-dry bin outside darkroom

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

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 29

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) 30 IP reader & data entry workstation post-processing workstation laser printer digital archive

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