RADIOGRAPHIC GRIDS

INVENTED BY DR. GUSTAV BUCKY 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

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

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

LEAD

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

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

SCATTER RADIATION-PRODUCED WITHIN THE PATIENT THROUGH _______INTERATION CAMPTON

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SCATTER TUBE

SCATTER SCATTER

GRID CONSTRUCTION

GRID RATIO G.R.= H/D

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

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

GRID RATIO VS CLEANUP RATIO SCATTER CLEAN-UP

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

NEW MAS= ORIGINAL MAS X NEW GRID FACTOR/OLD FACTOR GRID CONVERSIONS 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 NEW MAS= ORIGINAL MAS X NEW GRID FACTOR/OLD FACTOR

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

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

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

P-B DIAPHRAGM

GRIDS:

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

FOCUSED GRID

CROSSHATCH GRID

LINEAR GRID

LINEAR GRID USED IN TOMOGRAPHY

BIGGEST DISADVANTAGE OF LINEAR & CROSS GRID GRID CUT-OFF

GRID CUT-OFF

FOCUSED GRID

GRIDS

GRIDS

GRID INFO

GRID EFFICIENCY CIF GS

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

GS=NONSCATTER TRANSMITTED/SCATTER TRANSMITTED GRID SELECTIVITY GS=NONSCATTER TRANSMITTED/SCATTER TRANSMITTED

GRID ERRORS OFF LEVEL OFF CENTER OFF FOCUS UPSIDE DOWN 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

GRID ERRORS

GRID ERRORS

OFF FOCUS

UPSIDE DOWN

GRID ARTIFACTS MOIRE EFFECT STROBOSCOPIC EFFECT DAMAGED GRID

MOIRE EFFECT-PLACING GRID IN BUCKY MECHANISM

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

AIR GAP TECHNIQUE