BEAM RESTRICTOR DEVICES IS DESCRIBED IN DETAIL IN THIS PPT. CONTENT TAKEN FROM MULTIPLE BOOKS AND JOURNALS.

1. THE CONTROL OF
SCATTERED RADIATION
MR.ROHIT BANSAL
ASSISTANT PROFESSOR
(RADIOPHYSICS)

2. TOPICS INCLUDED :
•BASIC OVERVIEW OF X-RAY BEAM
•SCATTERED RADIATION & ITS TYPES
•BEAM LIMITING DEVICES
•BEAM CENTERING DEVICES
•GRIDS

3. BASIC OVERVIEW OF X-RAY BEAM
• X-RAY belongs to a group of radiation known as the
(ELECTROMAGNETIC RADIATIONS)
• All the electromagnetic radiations have dual
characteristics
• 1- Wave nature
• 2- Particle nature
• These are electromagnetic wave of high energy and
very short wavelength, which is able to pass through
many materials .

4. WAVELENGTH OF X RAY
Wavelength of X-RAY - 10−8 to 10−12 metre
Frequency ranges from -1016 to 1020 hertz (Hz)

5. SCATTERED RADIATION
• When useful beam interact with objects and then some of the
radiation reflects back that results in the production of
secondary beam called as scattered radiation

6. 1. OVERVIEW OF SCATTERING
•Scattering is mainly of 5 types
• Coherent scattering
• Compton scattering
• Photoelectric effect ( Mostly used in diagnostic
work)
• Photo disintegrating
• Pair productions

7. DISADVANTAGES OF
SCATTERED RADIATION :
• Basically, when X-RAY are penetrated then they cease to exit but
when they are scattered then they are deflected from there original
path and hence carry no useful information…
• At the end they only add up NOISE .
• And adds up the unwanted dose to the peoples present in the X-
RAY room .
• The end result is that the radiographic image is of a poor quality
which makes it difficult to diagnose it. Contrast of the film is also
degraded.

8. COMPARISON OF RADIOGRAPHIC IMAGES
Image without Image with
Scattered radiation Scattered radiation

9. MOST COMMON SOLUTION TO
DECREASE THE SCATTERED
RADIATION
• Filters
• Aperture diaphragms
• Cones and cylinders
• Collimators
• Beam centring devices
• Radiographic Grids
• Various devices used to reduce scattered radiation

10. FILTERS & FILTRATION
• FILTERS ARE THE DEVICES USED TO
ATTENUATE OR RESTRICTING THE BEAM
OF XRAY
• FILTRATION IS BASICALLY THE PROCESS
OF ATTENUATING OR SHAPING THE X -RAY
BEAM TO INCREASE THE AMOUNT OF
USEFUL PHOTONS AND DECREASE THE
LOW ENERGY PHOTONS SO THAT WE CAN
GET AN IMAGE WITH BETTER CONTRAST
• (FOR EXAMPLE – A STRAINER IS USED FOR
THE SEPARATION OF TEA PARTICLES AND
THE TEA )
• THIS ALSO DECREASE THE PATIENT
RADIATION DOSE AND OCCUPATIONAL
HAZARDS
• QUALITY OF X-RAY SPECTRUM SHIFTS TO
THE HIGHER ENERGY

11. HOW FILTRATION WORK
• W H E N E X P O S U R E I S D O N E T H E N B O T H H I G H A S W E L L
A S L O W E N E R G Y X - R AY P H O T O N S A R E P R O D U C E D .
• W H E N T H E S E X - R AY P H O T O N S I N T E R A C T W I T H T H E
H U M A N B O D Y, O N LY T H E H I G H E N E R G Y P H O T O N S
P E N E T R AT E W H I L E T H E L O W E N E R G Y P H O T O N S G E T
A B S O R B E D I N T H E B O D Y, H E N C E I N C R E A S I N G T H E
PAT I E N T R A D I AT I O N D O S E .
• F I LT R AT I O N B A S I C A L LY A B S O R B S T H E L O W E N E R G Y
P H O T O N S F R O M T H E B E A M A N D H E N C E I N C R E A S E S T H E
I M A G E C O N T R A S T.

13. LEVEL OF FILTRATION
• INHERENT FILTRATION
( X-RAY TUBE AND ITS HOUSING )
• ADDED FILTRATION
(SHEET OF METAL PIECE PLACED IN
THE PATH OF BEAM
• TOTAL FILTRATION
( TOTAL FILTRATION = INHERENT
FILTRATION + ADDED FILTRATION )

14. INHERENT FILTRATION
• THE ABSORPTION OF THE LOW ENERGY
X-RAY PHOTONS BY THE X-RAY TUBE
COMPONENTS ITSELF IS KNOWN AS THE
INHERENT FILTRATION.
• A GLASS HOUSING, METAL ENCLOSURE
AND THE ASSEMBLY OIL IS
RESPONSIBLE FOR INHERENT
FILTRATION.

15. CONT…
• BUT DISADVANTAGE OF INHERENT
FILTRATION IS THAT IT CAUSES A
SIGNIFICANT REDUCTION IN THE IMAGE
CONTRAST.
• AT SOME PLACES WHERE UNFILTERED X -
RAY BEAM IS REQUIRED THERE
BERYLLIUM FILTERS ARE MOSTLY USED.

17. ADDED FILTRATION
• A D D E D F I LT R AT I O N I S A R E S U LT O F A N Y B E A M
A B S O R B E R W H I C H I S P L A C E D I N T H E PAT H O F T H E X -
R AY B E A M , T H I S A B S O R B E R A B S O R B S T H E L O W O R
H I G H E N E R G Y P H O T O N S .
• T H I C K N E S S O F F I LT E R
B E L O W 5 0 K V P - 0 . 5 M M
5 0 - 7 0 K V P – 1 . 5 M M
A B O V E 7 0 - 2 . 5 M M )
• S O L U T I O N - W E A LWAY S U S E A D D E D F I LT E R S
M O S T LY I N A G R O U P O F A L U M I N I U M ( 1 3 ) +
C O P P E R ( 2 9 ) .

18. • T H E Y A R E A R R A N G E D A S T H E H I G H AT.
N O . ( C O P P E R )
E L E M E N T FA C E S T H E X - R AY T U B E W H I L E T H E
O T H E R ( A L U M I N I U M ) O N E FA C E S T H E PAT I E N T.
• M O S T O F T H E F I LT R AT I O N I S D O N E B Y C O P P E R .
• T H E Y C A N ' T B E U S E D S E PA R AT E LY.
• PAT I E N T R A D I AT I O N D O S E A S W E L L A S T H E I M A G E
C O N T R A S T I S R E D U C E D .
• T H I S C O M B I N AT I O N O F T W O L AY E R S O F F I LT E R S
I S A L S O K N O W N A S C O M P O U N D F I LT E R S .
CONT…….

20. TOTAL FILTRATION
• TOTAL FILTRATION REFERS TO THE SUM OF THE BOTH FILTRATION
DONE BY INHERENT FILTER & ADDED FILTER
SOME OTHER FILTERS ARE
ALSO COMMONLY USED ARE
:
• WEDGE FILTER
• K-EDGE FILTER

21. WEDGE FILTER
• Wedge filters are mostly used at places where the body
part to be radiographed varies greatly in densities.(thick
from one side and thin from another side)
• Wedge filters are like the shape of a wedge, the thin part is
placed under thick body part while thick part is placed
under thin body part.
• Result is that ,beam attenuation by thick part is more
hence less radiation reaches the part and beam
attenuation by thin part is less hence more radiation
reaches thick part.
• Therefore a radiograph of uniform density is got.

22. EG : DURING SPINE WHERE SPINE DENSITY VARY GREATLY
SO WEDGE FILTERS ARE USED
Real image of wedge filter

23. THICKNESS OF FILTER
• More will be the thickness of filters more will
be the attenuation of X-RAY by it.
• In other words;-
• ATTENUATION 0< FILTER
THICKNESS

24. K-EDGE FILTERS
• FILTERS WITH METALS OF
HIGH ATOMIC NUMBER.
• USUALLY USED WITH X-RAY
TUBES OF HIGH CAPACITY AND
HIGH SPEED INTRIGUING
SCREEN.
• THESE FILTERS BASICALLY
USE THE K-EDGE ABSORPTION
OF ELEMENT

25. X-RAY BEAM RESTRICTING
DEVICES
• BEAM RESTRICTION DEVICES INCLUDE: -
• APERTURE DIAPHRAGMS
• CONES AND CYLINDERS
• COLLIMATORS

26. A P E R T U R E D I A P H R A G M S
• T H E S E A R E B A S I C A L LY T H E S I M P L E S T X - R AY B E A M
R E S T R I C T O R S .
• I T I S M A D E O F A S H E E T O F L E A D W H I C H I S H AV I N G A
H O L E AT I T S C E N T R E .
• I T S A D VA N TA G E I S I T S S I M P L I C I T Y, I T C A N B E A LT E R E D
T O A N Y S H A P E O R S I Z E B E C A U S E L E A D I T I S S O F T.
• I T S D I S A D VA N TA G E I S T H AT I T P R O D U C E S A FA I R LY
L A R G E P E N U M B R A ( U N E X P O S E D A R E A O R S H A D O W )
• P E N U M B R A C A N B E R E D U C E D B Y P L A C I N G T H E
D I A P H R A G M FA R AWAY F R O M T H E X - R AY T U B E .
• T H E C E N T R E O F T H E X - R AY F I E L D I S E X P O S E D B Y T H E
C I R C U L A R A R E A .

27. APERTURE DIAPHRAGM

28. C O N E S A N D C Y L I N D E R S
• THESE RESTRICTORS ARE THE SHAPE OF CONES
AND CYLINDERS.
• THEY REDUCE THE UNEXPOSED AREA AT EDGES
BY REDUCING PENUMBRA
• THE FLARE OF THE CONE IS SIMILAR TO THE
GEOMETRIC SHAPE OF THE X-RAY BEAM, BUT IT
IS GREATER THAN THE FLARE OF THE X-RAY
BEAM.
• THEY ARE ATTACHED TO THE FRONT OF THE X -
RAY TUBE AND MAY ALSO BE EQUIPPED WITH
EXTENSIONS TO GIVE EVEN BETTER
RESTRICTION.

29. COMMANLY USED IN :- DENTAL AND
SKULL RADIOGRAPHS

30. ADVANTAGES
• INEXPENSIVE
• SIMPLE TO USE
• REDUCE PENUMBRA AND
OR FOCAL RADIATION
• PROVIDE BETTER BEAM
RESTRICTION AT A
GREATER DISTANCE AT A
FOCAL SPOT
DISADVANTAGE
• FIXED VIEWING AREA
• FLARED CONES ARE NO
BETTER AT REDUCING
PENUMBRA THAN
APERTURE DIAPHRAGMS

31. IMAGE WITHOUT CONE USE. IMAGE WITH CONE USE

32. C O L L I M AT O R S
C OLLIMATOR S AR E C ON SID ER ED TH E BEST BEAM
R ESTR IC TOR D EVIC ES.
IT IS HAVING TWO ADVANTAGES:
- IT PR OVID ES AN IN FIN ITE VAR IETY OF R EC TAN GU LAR
X- R AY FIELD S.
- IT ALSO SHOWS THE CENTRE POINT OF THE X - RAY
BEAM.
IT C ON SISTS OF TW O SETS OF SH U TTER S ( S1 & $2)
W H IC H MOVE IN OPPOSITE D IR EC TION S TO R EMOVE
TH E PEN U MBR A PR OD U C ED BY EAC H OTH ER .

33. S1
S2

35. GRIDS
GRIDS WERE INVENTED BY DR GUSTAVE BUCKY
IN 1913.
GRIDS ARE USED TO DECREASE THE
SCATTERED RADIATION.
GRIDS BASICALLY CONSISTS OF LEAD STRIPS
&
INTERSPACING MATERIAL (INTERSPACE IS
MADE UP OF
ORGANIC MATERIAL OR ALUMINIUM)
WHICH IS ALIGNED WITH THE GEOMETRY OF X -
RAY BEAM OF A PARTICULAR TUBE.

36. Outer top
View of
Grid
(Outer covering
of grid is made
up of aluminium)

38. GRID RATIO
• GRID RATIO IS DEFINED AS THE RATIO OF THE
HEIGHT OF THE LEAD STRIPS TO THE DISTANCE
BETWEEN THE LEAD STRIPS.
• GRID RATIO IS ALWAYS EXPRESSED AS E.G.
8:1(WHERE 8 IS THE ACTUAL RATIO AND THE
SECOND NO. IS ALWAYS ONE).
• IN RADIOLOGICAL GRIDS OF RATIO BETWEEN 4:1
TO 16:1
ARE GENERALLY USED.
• USUALLY THE THICKNESS OF LEAD STRIPS IS
ABOUT
O.05MM.

40. GRID PATTERNS / GRID TYPES
ON THE BASIS OF
MOVEMENT:
• STATIONARY GRID.
• AKA "Wafer" grids
• Produce x-rays that have very fine white
lines on them. These are the area of the
film that are blocked from receiving any
x-ray by the lead strips.
• To eliminate these grid lines" the
moving grid or Potter-Bucky diaphragm
was developed by Potter in 1913.
MOVING GRID
• THESE ARE THE
MODIFIED FOR OF
STATIONARY GRID
WITH A MOTOR
ATTACHED WITH THEN
WHICH ROTATE OR
MAKE THEM MOVE
ARE MOVING GRIDS

42. TYPES OF GRIDS
B A S I C A L LY T H E R E A R E T H R E E T Y P E S O F G R I D O N
T H E B A S I S O F S T R I P PAT T E R N :
1 - L I N E A R G R I D / PA R A L L E L G R I D
2 - C R O S S E D G R I D
3 - F O C U S E D G R I D
L I N E A R G R I D I S A G R I D I N W H I C H T H E L E A D S T R I P S
A R E P L A C E D PA R A L L E L TO E A C H O T H E R .
I T S A D VA N TA G E I S T H AT W H E N U S I N G L I N E A R G R I D
, T H E N W E C A N A N G L E T H E T U B E A L S O .
C R O S S E D G R I D I S F O R M E D W H E N T W O L I N E A R
G R I D S A R E O V E R L A P P E D W I T H E A C H O T H E R . I T
C A N N O T B E U S E D W I T H O B L I Q U E T E C H N I Q U E S .

44. FOCUSED GRID
• A FOC U SED GR ID IS A GR ID W H IC H IS MAD E U P OF
LEAD STR IPS W H IC H AR E AN GLED SLIGH TLY SO TH AT
TH EY FOC U S IN SPAC E.
• D ISTAN C E B/W TH E FOC U S AN D TH E LEAD STR IPS IS
KN OW N AS TH E FOC AL LEN GTH OF TH E GR ID

46. THANK YOU