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RADIOGRAPHIC GRIDSRADIOGRAPHIC GRIDS
GRIDSGRIDS
INVENTED BY DR. GUSTAV INVENTED BY DR. GUSTAV BUCKYBUCKY
GRIDSGRIDSDEVICES THAT REDUCE DEVICES THAT REDUCE
THE AMOUNT OF THE AMOUNT OF SCATTERED RADIATION SCATTERED RADIATION REACHING THE IMAGE REACHING THE IMAGE
RECEPTORRECEPTOR
GRIDS DO NOT REDUCE GRIDS DO NOT REDUCE THE AMOUNT OF THE AMOUNT OF
SCATTER RADIATION SCATTER RADIATION REACHING THE REACHING THE
IMAGING PERSONNELIMAGING PERSONNEL
GRIDS DO INCREASE GRIDS DO INCREASE RADIATION EXPOSURE RADIATION EXPOSURE
OF PATIENTSOF PATIENTS
FACTORS AFFECTING FACTORS AFFECTING SCATTER PRODUCTION SCATTER PRODUCTION WITHIN THE PATIENTWITHIN THE PATIENT
KILOVOLTAGEKILOVOLTAGE BEAM SIZEBEAM SIZE THICKNESS OF IRRADIATED TISSUETHICKNESS OF IRRADIATED TISSUE COMPOSITION OF IRRADIATED COMPOSITION OF IRRADIATED
TISSUETISSUE Z# OF IRRADIATED TISSUEZ# OF IRRADIATED TISSUE
GRIDS STRIPS GRIDS STRIPS ARE MADE OF ARE MADE OF
LEAD (Pb)LEAD (Pb) LEAD HAS Z#LEAD HAS Z#
AND ABSORBS SCATTER AND ABSORBS SCATTER RADIATION THROUGH RADIATION THROUGH
______ INTERACTION ______ INTERACTION PHOTOELECTRIC
LEADLEAD
GRIDSGRIDS
CONSCONS HIGHER PATIENT HIGHER PATIENT
DOSEDOSE
PROSPROS HIGHER HIGHER
CONTRASTCONTRAST INCREASED INCREASED
VISIBILITY OF VISIBILITY OF DETAIL DETAIL (CONTRAST (CONTRAST RESOLUTION)RESOLUTION)
GRID RADIOGRAPHY IS GRID RADIOGRAPHY IS RECOMMENDED FOR:RECOMMENDED FOR:
ANATOMICAL PARTS > 10 cmANATOMICAL PARTS > 10 cm WITH HIGH kVp ( NOT ALWAYS—WITH HIGH kVp ( NOT ALWAYS—
MAMMO)MAMMO) SOFT TSSUE STRUCTURES TO SOFT TSSUE STRUCTURES TO
INCREASE CONTRASTINCREASE CONTRAST STRUCTURES AFFECTED BY STRUCTURES AFFECTED BY
PATHOLOGICAL CONDITION THAT PATHOLOGICAL CONDITION THAT WOULD INCRESE SCATTER WOULD INCRESE SCATTER PRODUCTION PRODUCTION
SCATTER RADIATION-SCATTER RADIATION-PRODUCED WITHIN PRODUCED WITHIN
THE PATIENT THROUGH THE PATIENT THROUGH _______INTERATION_______INTERATION
CAMPTON
--
-- --
SCATTERSCATTERTUBE
SCATTERSCATTER
SCATTER
GRID CONSTRUCTIONGRID CONSTRUCTION
GRID RATIOGRID RATIO
G.R.= H/DG.R.= H/D
GRID SURFACE X-RAY GRID SURFACE X-RAY ABSORPTION—TYPICAL ABSORPTION—TYPICAL
GRID STRIPS-50 GRID STRIPS-50 MICROMETERSMICROMETERS
INTERSPACE –350 INTERSPACE –350 MICROMETERSMICROMETERS
X-RAY ABSORPTION (%)= X-RAY ABSORPTION (%)= WIDTH OF STRIPS X WIDTH OF STRIPS X 100100
WIDTH OF STRIPS + WIDTH OF INTERSPACEWIDTH OF STRIPS + WIDTH OF INTERSPACE
HIGH QUALITY GRIDS HIGH QUALITY GRIDS CAN ATTENUATE 80%-CAN ATTENUATE 80%-
90% OF SCATTER 90% OF SCATTER RADIATIONRADIATION
GRID RATIO VS GRID RATIO VS CLEANUPCLEANUP
RATIORATIO SCATTER CLEAN-SCATTER CLEAN-UPUP
BUCKY FACTORBUCKY FACTOR
BF=I.R./T.R.BF=I.R./T.R.
GRID CONVERSIONSGRID CONVERSIONS
NO GRIDNO GRID 5:15:1 8:18:1 12:112:1 16:116:1
1 X MAS , KVP X 11 X MAS , KVP X 1 2 X MAS , + 8-10 2 X MAS , + 8-10
KVPKVP 4 X MAS , + 12-15 4 X MAS , + 12-15
KVPKVP 5 X MAS , + 20-25 5 X MAS , + 20-25
KVPKVP 6 X MAS , + 30-40 6 X MAS , + 30-40
KVPKVPNEW MAS= ORIGINAL MAS X NEW GRID FACTOR/OLD FACTOR
GRID FREQUENCYGRID FREQUENCY
# OF LEAD STRIPS PER # OF LEAD STRIPS PER INCH OR CMINCH OR CM
G.F.= 10,000 MICROMETERS/CM
T + D MICROMETER/LINE PAIR
T-STRIP WIDTHD-INTERSPACE WIDTH
GRID TYPESGRID TYPES
STATIONARYSTATIONARY MOVING-MOVING-SINGLE STROKESINGLE STROKE && RECIPROCATINGRECIPROCATING
LINEARLINEAR CROSSHATCHCROSSHATCH FOCUSEDFOCUSED
MOVING GRID DR. MOVING GRID DR. HOLLIS POTTER HOLLIS POTTER
MODIFIED BUCKY MODIFIED BUCKY DIAPHGRAMDIAPHGRAM
POTTER-BUCKY POTTER-BUCKY DIAPHGRAMDIAPHGRAM
P-B DIAPHRAGMP-B DIAPHRAGM
GRIDS:GRIDS:
CANTINGCANTINGTILTING OF THE LEAD TILTING OF THE LEAD
STRIPS TO CREATE STRIPS TO CREATE FOCUSED GRIDFOCUSED GRID
FOCUSED GRIDFOCUSED GRID
CROSSHATCH GRIDCROSSHATCH GRID
LINEAR GRIDLINEAR GRID
LINEAR GRID USED IN LINEAR GRID USED IN TOMOGRAPHYTOMOGRAPHY
BIGGEST BIGGEST DISADVANTAGE DISADVANTAGE
OF LINEAR & OF LINEAR & CROSS GRIDCROSS GRID
GRID CUT-OFFGRID CUT-OFF
GRID CUT-OFFGRID CUT-OFF
FOCUSED GRIDFOCUSED GRID
GRIDSGRIDS
GRIDSGRIDS
GRID INFOGRID INFO
GRID EFFICIENCYGRID EFFICIENCY
CIFCIF GSGS
CONTRAST IMPROVEMENT CONTRAST IMPROVEMENT FACTORFACTOR
CIF= CONTRAST WITH GRID/CONTRAST WITHOUT GRID
GRID SELECTIVITYGRID SELECTIVITY
GS=NONSCATTER TRANSMITTED/SCATTER TRANSMITTED
GRID ERRORSGRID ERRORS OFF LEVEL OFF LEVEL
OFF CENTEROFF CENTER
OFF FOCUSOFF FOCUS
UPSIDE DOWNUPSIDE DOWN
OFF FOCUS & OFF CENTEROFF FOCUS & OFF CENTER
CUTOOF ACROSS ENTIRE CUTOOF ACROSS ENTIRE IMAGE, LIGHT IMAGEIMAGE, LIGHT IMAGE
CUTOOF ACROSS ENTIRE CUTOOF ACROSS ENTIRE IMAGE, LIGHT IMAGEIMAGE, LIGHT IMAGE
CUTOFF TOWARD THE CUTOFF TOWARD THE EDGE OF THE IMAGEEDGE OF THE IMAGE
SEVERE CUTOFF TOWARD SEVERE CUTOFF TOWARD THE EDGE OF THE IMAGETHE EDGE OF THE IMAGE
DARK ON ONE SIDE & DARK ON ONE SIDE & LIGHT ON THE OTHERLIGHT ON THE OTHER
GRID ERRORSGRID ERRORS
GRID ERRORSGRID ERRORS
OFF FOCUSOFF FOCUS
UPSIDE DOWNUPSIDE DOWN
GRID ARTIFACTSGRID ARTIFACTS
MOIRE EFFECTMOIRE EFFECT STROBOSCOPIC EFFECTSTROBOSCOPIC EFFECT DAMAGED GRIDDAMAGED GRID
MOIRE EFFECT-MOIRE EFFECT-PLACING GRID PLACING GRID IN BUCKY MECHANISMIN BUCKY MECHANISM
STROBOSCOPIC EFFECT STROBOSCOPIC EFFECT (MOVING GRIDS) -MOTION (MOVING GRIDS) -MOTION OF THE GRID IS FROZENOF THE GRID IS FROZEN
WHEN USING SHORT EXPOSURE TIME ( SHORTER THAN WHEN USING SHORT EXPOSURE TIME ( SHORTER THAN
MOVEMENT OF THE GRIDMOVEMENT OF THE GRID) )
RECIPROCATING MECHANISM IS BROKENRECIPROCATING MECHANISM IS BROKEN
AIR GAP TECHNIQUEAIR GAP TECHNIQUE
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