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

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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