Download 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
FACTORS AFFECTING SCATTER
PRODUCTION WITHIN THE
PATIENT
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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 ______
PHOTOELECTRIC
INTERACTION
LEAD
GRIDS
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CONS
HIGHER PATIENT
DOSE
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PROS
HIGHER CONTRAST
INCREASED
VISIBILITY OF
DETAIL (CONTRAST
RESOLUTION)
GRID RADIOGRAPHY IS
RECOMMENDED FOR:
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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 RADIATIONPRODUCED WITHIN THE
PATIENT THROUGH
_______INTERATION
CAMPTON
--
--
--
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
WIDTH OF STRIPS + WIDTH OF INTERSPACE
X 100
HIGH QUALITY GRIDS CAN
ATTENUATE 80%-90% OF
SCATTER RADIATION
GRID RATIO VS CLEANUP
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RATIO
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SCATTER CLEAN-UP
BUCKY FACTOR
BF=I.R./T.R.
GRID CONVERSIONS
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NO GRID
5:1
8:1
12:1
16:1
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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
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STATIONARY
MOVING-SINGLE STROKE & RECIPROCATING
LINEAR
CROSSHATCH
FOCUSED
MOVING GRID DR. HOLLIS
POTTER MODIFIED BUCKY
DIAPHGRAM
POTTER-BUCKY
DIAPHGRAM
P-B DIAPHRAGM
GRIDS:
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
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CIF
GS
CONTRAST IMPROVEMENT
FACTOR
CIF= CONTRAST WITH GRID/CONTRAST WITHOUT GRID
GRID SELECTIVITY
GS=NONSCATTER TRANSMITTED/SCATTER TRANSMITTED
GRID ERRORS
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OFF LEVEL
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OFF CENTER
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OFF FOCUS
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UPSIDE DOWN
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OFF FOCUS & OFF CENTER
CUTOOF ACROSS ENTIRE
IMAGE, LIGHT IMAGE
CUTOOF ACROSS ENTIRE
IMAGE, LIGHT IMAGE
CUTOFF TOWARD THE EDGE OF
THE IMAGE
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SEVERE CUTOFF TOWARD THE
EDGE OF THE IMAGE
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DARK ON ONE SIDE & LIGHT
ON THE OTHER
GRID ERRORS
GRID ERRORS
OFF FOCUS
UPSIDE DOWN
GRID ARTIFACTS
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MOIRE EFFECT
STROBOSCOPIC EFFECT
DAMAGED GRID
MOIRE EFFECT-PLACING GRID IN
BUCKY MECHANISM
STROBOSCOPIC EFFECT
(MOVING GRIDS) -MOTION OF
THE GRID IS FROZEN
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WHEN USING SHORT EXPOSURE TIME ( SHORTER THAN MOVEMENT
OF THE GRID
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)
RECIPROCATING MECHANISM IS BROKEN
AIR GAP TECHNIQUE