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RADIOGRAPHIC GRIDS. GRIDS INVENTED BY DR. GUSTAV BUCKY.

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Presentation on theme: "RADIOGRAPHIC GRIDS. GRIDS INVENTED BY DR. GUSTAV BUCKY."— Presentation transcript:

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 KILOVOLTAGE BEAM SIZE BEAM SIZE THICKNESS OF IRRADIATED TISSUE THICKNESS OF IRRADIATED TISSUE COMPOSITION OF IRRADIATED TISSUE COMPOSITION OF IRRADIATED TISSUE Z# OF IRRADIATED TISSUE Z# OF IRRADIATED TISSUE

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

8 LEAD

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

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

11 SCATTER RADIATION- PRODUCED WITHIN THE PATIENT THROUGH _______INTERATION CAMPTON

12

13 --

14 SCATTER TUBE

15 SCATTER SCATTER

16 GRID CONSTRUCTION

17 GRID RATIO G.R.= H/D

18 GRID SURFACE X-RAY ABSORPTIONTYPICAL GRID STRIPS-50 MICROMETERS INTERSPACE –350 MICROMETERS GRID SURFACE X-RAY ABSORPTIONTYPICAL GRID STRIPS-50 MICROMETERS INTERSPACE –350 MICROMETERS X-RAY ABSORPTION (%)= WIDTH OF STRIPS X 100 WIDTH OF STRIPS + WIDTH OF INTERSPACE WIDTH OF STRIPS + WIDTH OF INTERSPACE

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

20 GRID RATIO VS CLEANUP RATIO RATIO SCATTER CLEAN-UP

21 BUCKY FACTOR BF=I.R./T.R.

22 GRID CONVERSIONS NO GRID NO GRID 5:1 5:1 8:1 8:1 12:1 12:1 16:1 16:1 1 X MAS, KVP X 1 2 X MAS, KVP 4 X MAS, KVP 5 X MAS, KVP 6 X MAS, KVP NEW MAS= ORIGINAL MAS X NEW GRID FACTOR/OLD FACTOR

23 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

24 GRID TYPES STATIONARY STATIONARY MOVING- SINGLE STROKE & RECIPROCATING MOVING- SINGLE STROKE & RECIPROCATING LINEAR LINEAR CROSSHATCH CROSSHATCH FOCUSED FOCUSED

25 MOVING GRID DR. HOLLIS POTTER MODIFIED BUCKY DIAPHGRAM POTTER-BUCKY DIAPHGRAM

26 P-B DIAPHRAGM

27 GRIDS: GRIDS:

28 CANTING TILTING OF THE LEAD STRIPS TO CREATE FOCUSED GRID

29 FOCUSED GRID

30 CROSSHATCH GRID

31 LINEAR GRID

32 LINEAR GRID USED IN TOMOGRAPHY

33 BIGGEST DISADVANTAGE OF LINEAR & CROSS GRID GRID CUT-OFF

34

35 FOCUSED GRID

36 GRIDS

37 GRIDS

38 GRID INFO

39 GRID EFFICIENCY CIF CIF GS GS

40 CONTRAST IMPROVEMENT FACTOR CIF= CONTRAST WITH GRID/CONTRAST WITHOUT GRID

41 GRID SELECTIVITY GS=NONSCATTER TRANSMITTED/SCATTER TRANSMITTED

42 GRID ERRORS OFF LEVEL OFF LEVEL OFF CENTER OFF CENTER OFF FOCUS OFF FOCUS UPSIDE DOWN UPSIDE DOWN OFF FOCUS & OFF CENTER OFF FOCUS & OFF CENTER 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

43 GRID ERRORS

44

45 OFF FOCUS

46 UPSIDE DOWN

47 GRID ARTIFACTS MOIRE EFFECT MOIRE EFFECT STROBOSCOPIC EFFECT STROBOSCOPIC EFFECT DAMAGED GRID DAMAGED GRID

48 MOIRE EFFECT- PLACING GRID IN BUCKY MECHANISM

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

50 AIR GAP TECHNIQUE


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