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RADIOGRAPHIC GRIDS

RADIOGRAPHIC GRIDS. GRIDS. INVENTED BY DR. GUSTAV BUCKY. GRIDS. DEVICES THAT REDUCE THE AMOUNT OF SCATTERED RADIATION REACHING THE IMAGE RECEPTOR. GRIDS DO NOT REDUCE THE AMOUNT OF SCATTER RADIATION REACHING THE IMAGING PERSONNEL. GRIDS DO INCREASE RADIATION EXPOSURE OF PATIENTS.

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RADIOGRAPHIC GRIDS

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  1. RADIOGRAPHIC GRIDS

  2. GRIDS INVENTED BY DR. GUSTAV BUCKY

  3. GRIDS DEVICES THAT REDUCE THE AMOUNT OF SCATTERED RADIATION REACHING THE IMAGE RECEPTOR

  4. GRIDS DO NOT REDUCE THE AMOUNT OF SCATTER RADIATION REACHING THE IMAGING PERSONNEL

  5. GRIDS DO INCREASE RADIATION EXPOSURE OF PATIENTS

  6. FACTORS AFFECTING SCATTER PRODUCTION WITHIN THE PATIENT • KILOVOLTAGE • BEAM SIZE • THICKNESS OF IRRADIATED TISSUE • COMPOSITION OF IRRADIATED TISSUE • Z# OF IRRADIATED TISSUE

  7. GRIDS STRIPS ARE MADE OF LEAD (Pb) PHOTOELECTRIC LEAD HAS Z# AND ABSORBS SCATTER RADIATION THROUGH ______ INTERACTION

  8. LEAD

  9. CONS HIGHER PATIENT DOSE PROS HIGHER CONTRAST INCREASED VISIBILITY OF DETAIL (CONTRAST RESOLUTION) GRIDS

  10. GRID RADIOGRAPHY IS RECOMMENDED FOR: • ANATOMICAL PARTS > 10 cm • WITH HIGH kVp ( NOT ALWAYS—MAMMO) • SOFT TSSUE STRUCTURES TO INCREASE CONTRAST • STRUCTURES AFFECTED BY PATHOLOGICAL CONDITION THAT WOULD INCRESE SCATTER PRODUCTION

  11. SCATTER RADIATION-PRODUCED WITHIN THE PATIENT THROUGH _______INTERATION CAMPTON

  12. -- -- --

  13. SCATTER TUBE

  14. SCATTER SCATTER

  15. GRID CONSTRUCTION

  16. GRID RATIOG.R.= H/D

  17. GRID SURFACE X-RAY ABSORPTION—TYPICAL GRID STRIPS-50 MICROMETERSINTERSPACE –350 MICROMETERS X-RAY ABSORPTION (%)= WIDTH OF STRIPS X 100 WIDTH OF STRIPS + WIDTH OF INTERSPACE

  18. HIGH QUALITY GRIDS CAN ATTENUATE 80%-90% OF SCATTER RADIATION

  19. RATIO SCATTER CLEAN-UP GRID RATIO VS CLEANUP

  20. BUCKY FACTORBF=I.R./T.R.

  21. NO GRID 5:1 8:1 12:1 16:1 1 X MAS , KVP X 1 2 X MAS , + 8-10 KVP 4 X MAS , + 12-15 KVP 5 X MAS , + 20-25 KVP 6 X MAS , + 30-40 KVP GRID CONVERSIONS NEW MAS= ORIGINAL MAS X NEW GRID FACTOR/OLD FACTOR

  22. GRID FREQUENCY# OF LEAD STRIPS PER INCH OR CM G.F.= 10,000 MICROMETERS/CM T + D MICROMETER/LINE PAIR T-STRIP WIDTH D-INTERSPACE WIDTH

  23. GRID TYPES • STATIONARY • MOVING-SINGLE STROKE&RECIPROCATING • LINEAR • CROSSHATCH • FOCUSED

  24. MOVING GRID DR. HOLLIS POTTER MODIFIED BUCKY DIAPHGRAMPOTTER-BUCKY DIAPHGRAM

  25. P-B DIAPHRAGM

  26. GRIDS:

  27. CANTING TILTING OF THE LEAD STRIPS TO CREATE FOCUSED GRID

  28. FOCUSED GRID

  29. CROSSHATCH GRID

  30. LINEAR GRID

  31. LINEAR GRID USED IN TOMOGRAPHY

  32. BIGGEST DISADVANTAGE OF LINEAR & CROSS GRID GRID CUT-OFF

  33. GRID CUT-OFF

  34. FOCUSED GRID

  35. GRIDS

  36. GRIDS

  37. GRID INFO

  38. GRID EFFICIENCY • CIF • GS

  39. CONTRAST IMPROVEMENT FACTOR CIF= CONTRAST WITH GRID/CONTRAST WITHOUT GRID

  40. GRID SELECTIVITY GS=NONSCATTER TRANSMITTED/SCATTER TRANSMITTED

  41. OFF LEVEL OFF CENTER OFF FOCUS UPSIDE DOWN OFF FOCUS & OFF CENTER CUTOOF ACROSS ENTIRE IMAGE, LIGHT IMAGE CUTOOF ACROSS ENTIRE IMAGE, LIGHT IMAGE CUTOFF TOWARD THE EDGE OF THE IMAGE SEVERE CUTOFF TOWARD THE EDGE OF THE IMAGE DARK ON ONE SIDE & LIGHT ON THE OTHER GRID ERRORS

  42. GRID ERRORS

  43. GRID ERRORS

  44. OFF FOCUS

  45. UPSIDE DOWN

  46. GRID ARTIFACTS • MOIRE EFFECT • STROBOSCOPIC EFFECT • DAMAGED GRID

  47. MOIRE EFFECT-PLACING GRID IN BUCKY MECHANISM

  48. STROBOSCOPIC EFFECT (MOVING GRIDS) -MOTION OF THE GRID IS FROZEN • WHEN USING SHORT EXPOSURE TIME ( SHORTER THAN MOVEMENT OF THE GRID) • RECIPROCATING MECHANISM IS BROKEN

  49. AIR GAP TECHNIQUE

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