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1. { MODERATOR: DR.RAMAKANTH
PRESENTOR : DR.PREETHI
SCATTER RADIATION,
FILTERS,
GRIDS

2.  WHEN A PHOTON BEAM INTERACTS
WITH MATTER, SOME PHOTON GETS
ABSORBED, SOME DEFLECTED, AND REST
IS TRANSMITTED TO PRODUCE A
RADIOGRAPHIC IMAGE
 THE PART WHICH IS DEFLECTED FROM ITS
ORIGINAL PATH TO A NEW DIRECTION IS
SCATTER RADIATION
INTRODUCTION

3.  SCATTER RADIATION ONLY ADDS UP TO UNWANTED DENSITIES
(NOISE) IN FILM
 THE END RESULT IS THAT THE RADIOGRAPHIC IMAGE IS OF A
POOR QUALITY WITH DECREASED CONTRAST
DISADVANTAGES

5.  INCREASE IN FIELD SIZE
 INCREASE IN PART THICKNESS
 INCREASE IN KVP
CAUSE OF INCREASE IN
SCATTER RADIATION

6.  WHEN FIELD SIZE IS NARROW, ONLY A
SMALL VOLUME OF TISSUE IS
IRRADIATED AND SO IT GENERATES A
SMALL NUMBER OF SCATTER
RADIATION
 WHEN THE FIELD SIZE INCREASES,
SCATTER RADIATION TOO INCREASES
INITIALLY THEN REACHES A PLATEAU
 THIS SATURATION POINT FOR SCATTER
RADIATION OCCURS WITH A FIELD OF
APPROX. 30 * 30 CM
FIELD SIZE

7.  AS THE PART THICKNESS
INCREASES SCATTER RADIATON
TOO INCREASES UPTO A CERATAIN
EXTENT AND THEN SATURATION
OCCURS
 THIS SATURATION IS BECAUSE
PHOTONS ORIGINATING IN THE
UPPER LAYERS OF THE PATIENT DO
NOT HAVE SUFFICIENT ENERGY TO
REACH THE FILM
PATIENT THICKNESS

8.  IN A LOW ENERGY RANGE-
PHOTOELECTRIC EFFECT
PREDOMINATES- LITTLE
SCATTER RADIATION IS
PRODUCED
 AS ENERGY INCREASES
COMPTON EFFECT
PREDOMINATES- SCATTER
RADIATION INCREASES
KVP

10.  FILTERS
 APERTURE DIAPHRAMS
 CONES AND CYLINDERS
 COLLIMATORS
 BEAM CENTERING DEVICES
 RADIOGRAPHIC GRIDS
WAYS TO DECREASE
SCATTER RADIATION

11.  FILTRATION IS A PROCESS OF SHAPING
THE X RAY BEAM TO INCREASE THE
PHOTONS USEFUL FOR IMAGING.
 IT ALSO DECREASES THE PATIENT DOSE
AND FILTERS THE LOW ENERGY
PHOTONS IN ORDER TO IMPROVE THE
IMAGE CONTRAST.
FILTERS

12.  DIAGNOSTIC X RAY BEAMS ARE POLYCHROMATIC.
 HIGH ENERGY PHOTONS PENETRATE THE BODY PART TO
PRODUCE A RADIO GRAPHIC IMAGE WHILE LOW ENERGY
PHOTONS GETS ABSORBED IN THE BODY, THUS INCREASING
THE PATIENT RADIATION DOSE.
 FILTRATION ABSORBS THIS LOW ENERGY PHOTONS AND
INCREASES THE IMAGE CONTRAST.
HOW FILTRATION WORKS

14.  INHERENT FILTRATION
 ADDED FILTRATION
 THE PATIENT
LEVELS OF FILTRATION

15.  ABSORPTION OF LOW ENERGY X RAY PHOTONS BY THE X
RAY TUBE COMPONENTS ITSELF IS INHERENT FILTRATION.
 MATERIALS: GLASS ENVELOPE, INSULATING OIL, WINDOW
IN TUBE HOUSING.
 MEASURED IN : ALUMINIUM EQUIVALENT ( 0.5 TO 1 MM ).
 DISADVANTAGE : INCREASES THE MEAN ENERGY,
DECREASE THE TISSUE CONTRAST.
 BERYLLIUM IS USED AS A EXIT PORTAL IN SOME
CIRCUMSTANCES WHERE UNFILTERED RADIATION IS
DESIRABLE
INHERENT FILTRATION

17.  ADDED FILTRATION IS A RESULT OF ANY BEAM ABSORBER
THAT IS PLACED IN THE PATH OF THE XRAY BEAM
 IDEAL FILTER DOES NOT EXIST
 MATERIALS: ALUMINUM AND COPPER.
 ALUMINIUM (13) ABSORBS LOW ENERGY PHOTONS AND
FACES THE PATIENT
 COPPER (29) ABSORBS HIGH ENERGY PHOTONS AND FACES
XRAY TUBE
ADDED FILTRATION

18.  MOST FILTRATION OCCURS IN COPPER
 WHY ALUMINUM ? IT ABSORBS CHARACTERISTIC
RADIATION OF 8 KEV PRODUCED BY PHOTO ELECTRIC
EFFECT IN COPPER.
 THICKNESS : 2 MM THICKNESS ABSORBS ALL PHOTONS WITH
ENERGY < 20 KEV.
 AS FURTHER THICKNESS INCREASES EVEN HIGH ENERGY
PHOTONS ARE ABSORBED RESULTING IN DECREASED
INTENSITY AND MORE EXPOSURE TIME.

20.  THEY ARE USED AT
PLACES OF DIFFERING
BODY PART THICKNESS
IN ORDER TO PRODUCE
A RADIO GRAPHIC
IMAGE OF UNIFORM
DENSITY.
WEDGE FILTERS

21.  THESE ARE METALS WITH HIGH ATOMIC NUMBER > 60
EXCEPT Mo.
 THESE FILTERS USE THE K- EDGE ABSORPTION OF THE
ELEMENT.
 USE : IT ALLOWS ONLY THE XRAY BEAM WITH SPECIFIC
ENERGY RANGE.
 THERE IS PRODUCTION OF A NARROW SPECTRUM, WITH
REDUCTION OF BOTH LOW AND HIGH ENERGY PHOTONS.
HEAVY METAL FILTERS ( K
EDGE FILTERS)

22.  USED IN MAMMOGRAPHY AS A TARGET
AND FILTER.
 AS A TARGET IT PRODUCES 17.5 KEV K
ALPHA AND 19.6 KEV K BETA
CHARACTERISTIC RADIATION.
 ALSO PRODUCES X RAY RADIATION WITH
ENERGIES MORE THAN 20 KEV, WHEN LOW
KVP ( 30 -40) TECHNIQUE IS USED.
 TO ABSORB THIS HIGH ENERGY
RADIATION, MOLYBDENUM IS USED AS A
FILTER.
MOLYBDENUM

23.  GRIDS CONSISTS OF A SERIES OF LEAD FOIL STRIPS
SEPARATED BY XRAY TRANSPARENT SPACERS
 INVENTED BY DR. GUSTAVE BUCKY
 THE INTERSPACES ARE FILLED WITH ALUMINUM OR SOME
ORGANIC COMPOUND.
 GRID IS POSITIONED BETWEEN THE PATIENT AND THE
IMAGE RECEPTOR.
 THE GRID ID DESIGNED TO TRANSMIT ONLY THOSE X RAYS
WHOSE DIRECTION IS ON STRAIGHT LINE FROM SOURCE TO
IR.
GRIDS

26.  LINEAR GRID
 CROSSED GRID
 PARALLEL GRID
 FOCUSED GRID
PATTERNS OF GRID

27.  LEAD STRIPS ARE PARALLEL TO EACH
OTHER IN LONGITUDINAL AXIS
 ADVANTAGE : THEY ALLOW US TO
ANGLE THE XRAY TUBE ALONG THE
LENGTH OF THE GRID WITHOUT THE
LOSS OF PRIMARY RADIATION.
LINEAR GRID

28.  MADE OF 2 SUPER IMPOSED LINEAR
GRIDS THAT HAVE THE SAME FOCUSING
DISTANCE.
 GRID RATIO OF CROSSED GRIS IS EQUAL
TO THE SUM OF 2 LINEAR GRIDS.
 DISADVANTAGE : CANNOT BE USED
WITH OBLIGE TECHNIQUES REQUIRING
ANGULATION OF THE X RAY TUBE
CROSSED GRID

29.  GRID MADE UP OF LEAD STRIPS THAT ARE
SLIGHTLY ANGLED SO THAT THEY FOCUS
IN SPACE
 MAY BE EITHER LINEAR OR CROSSED
 LINEAR GRIDS FOCUS AT CONVERGENT
LINE
 CROSS GRIDS FOCUS AT CONVERGENT
POINT
FOCUSED GRID

30.  LEAD STRIPS ARE PARALLEL WHEN VIEWED IN
CROSS SECTION
 FOCUSED AT INFINITY
 USED IN FLUOROSCOPY
PARALLEL GRID

31. GRID RATIO

32.  NUMBER OF LEAD STRIPS PER
INCH OF THE GRID
 CALCULATED BY ADDING THE
THICKNESS OF THE LEAD
STRIPS AND INTER SPACES AND
DIVIDING THIS SUM INTO 1
LINES PER INCH

33.  PRIMARY TRANSMISSION
 BUCKY FACTOR
 CONTRAST IMPROVEMENT FACTOR
EVALUATION OF GRID
PERFORMANCE

34.  MEASUREMENT OF PERCENTAGE OF PRIMARY RADIATION
TRANSMITTED THROUGH THE GRID.
 Tp = lp/lp' x 100
PRIMARY TRANSMISSION

35.  RATIO OF THE INCIDENT RADIATION ON THE
GRID TO THE TRANSMITTED RADIATION
PASSING THROUGH THE GRID
 MEASURE OF THE GRIDS ABILITY TO ABSORB
SCATTER RADIATION
 UNLIKE PRIMARY TRANSMISSION, BUCKY
FACTOR INDICATES THE ABSORPTION OF
BOTH PRIMARY AND SECONDARY RADIATION
BUCKY FACTOR

36.  RATIO OF THE CONTRAST WITH A GRID TO THE CONTRAST
WITHOUT A GRID
 MEASURE OF THE GRIDS ABILITY TO IMPROVE CONTRAST
 IT DEPENDS ON
-KVP
-FIELD SIZE
-PHANTOM THICKNESS
CONTRAST
IMPROVEMENT FACTOR

37.  LOSS OF PRIMARY RADIATION THAT OCCURS WHEN THE
IMAGES IF THE LEAD STRIPS ARE PROJECTED WIDER THAN
THEY WOULD BE WITH ORDINARY MAGNIFICATION
 RESULT OF A POOR GEOMETRIC RELATIONSHIP BETWEEN
THE PRIMARY BEAM AND THE LEAD FOIL STRIPS OF THE
GRID
 CUTOFF IS COMPLETE AND NO PRIMARY RADIATION
REACHES THE FILM WHEN THE PROJECTED IMAGES OF THE
LEAD STRIPS ARE THICKER THAN THE WIDTH OF THE
INTERSPACES
GRID CUT OFF

38. AMOUNT OF CUTOFF IS ALWAYS GREATEST WITH HIGH RATIO
GRIDS AND SHORT GRID FOCUS DISTANCES
SITUATIONS THAT PRODUCE GRID CUTOFF
 FOCUSSED GRIDS USED UPSIDE DOWN
 LATERAL DECENTERING(GRID ANGULATION)-OFF CENTER
 FOCUS GRID DISTANCE DECENTERING- OFF FOCUS
 COMBINED LATERAL AND FOCUS GRID DISTANCE
DECENTERING

40.  THIS OCCURS WHEN A FOCUSSED GRID IS PLACED UPSIDE
DOWN ON THE IMAGE RECEPTOR, RESULTING IN THE GRID
LINES GOING OPPOSITE THE ANGLE OF DIVERGENCE OF THE
XRAY BEAM
 RADIOGRAPHICALLY, THERE IS SIGNIFICANT LOSS OF
EXPOSURE ALONG THE EDGES OF THE IMAGE
UPSIDE DOWN FOCUSSED
GRIDS

41.  PHOTONS EASILY PASS THROUGH THE
CENTER OF THE GRID BECAUSE THE
LEAD LINES ARE PERPENDICULAR TO
THE IMAGE RECEPTOR SURFACE
 THE TILTED STRIPS NEAR THE EDGES
OF THE GRID WILL ABSORB
PROGRESSIVELY MORE RADIATION
CAUSING SEVERE PERIPHERAL CUTOFF
 HOWEVER WITH PARALLEL GRIDS
EITHER SIDE MAY FACE THE TUBE OR
FILM

42.  IT OCCURS WHEN THE CENTRAL RAY OF XRAY BEAM
IS NOT ALIGNED FROM SIDE TO SIDE WITH THE
CENTER OF FOCUSSED GRID
 ALL THE LEAD STRIPS CUTOFF THE SAME AMOUNT
OF PRIMARY RADIATION
 HENCE THERE IS UNIFORM LOSS OF RADIATION
OVER THE ENTIRE SURFACE OF THE GRID,
PRODUCING A UNIFORMLY LIGHT RADIOGRAPH
LATERAL DECENTERING-
OFF CENTER

43.  TARGET OF THE XRAY TUBE IS
CORRECTLY CENTERED TO THE GRID
BUT IS POSITIONED ABOVE OR BELOW
THE CONVERGENT LINE
FOCUS GRID DISTANCE
DECENTERING- OFF FOCUS

44.  CAUSES AN UNEVEN EXPOSURE , RESULTING IN A FIL THAT
IS DARK ON ONE SIDE AND LIGHT ON THE OTHER SIDE
COMBINED OFF CENTER
AND OFF FOCUSSED

45.  OFF LEVEL GRID CUTOFF RESULTS
WHEN THE XRAY BEAM IS ANGLED
ACROSS THE LEAD STRIPS
 OCCUR FROM EITHER A TUBE OR
THE GRID BEING ANGLED
 OFTEN SEEN WITH PORTABLE
RADIOGRRAPH OR HORIZONTAL
BEAM EXAMINATIONS
 OCCURS ONLY WITH BOTH
FOCUSSED AND PARALLEL GRIDS
OFF LEVEL GRIDS

46.  FOCUSSED GRIDS ARE USUALLY USED
 PLACED IN HOLDING MECHANISM THAT
BEGINS MOVING JUST BEFORE XRAY EXPOSURE
AND CONTINUES MOVING AFTER END OF
EXPOSURE
 MOVES 1-3 INCHES
 MOTION BLURS OUT THE GRID STRIPS
MOVING GRIDS

47.  SINGLE STROKE: GRID HAD TO BE COCKED WITH A SPRING
MECHANISM
 RECIPROCATING GRID: A MOTOR DRIVES THE GRID BACK
AND FORTH DURING THE EXPOSURE
 OSCILLATING GRID: MOVES IN A CIRCULAR MOTION
AROUND THE GRID FRAME. DELICATE , SPRING LIKE
DEVICES LOCATED IN THE FOUR CORNERS HOLD THE GRID
CENTERED WITHIN THE FRAME
TYPES OF MOVING GRIDS

48. ADVANTAGES:
 NO GRID LINES ARE SEEN
 MOTION BLUR IS
UNDETECTABLE
DISADVANTAGES:
 COSTLY
 MECHANICAL PROBLEMS
MAY OCCUR
 INCREASE THE PATIENT
RADIATION DOSE