X-RAY GRID BUCKY

X-RAY GRID
/BUCKY
REFERRED BY:
THAYALAN SIR
-BOOK AND
CHRISTENSEN’S BOOK

GRID
 GRID IS A DEVICE WHICH REDUCES THE AMOUNT OF SACTTERED
RADIATION REACHING THE FILM.
 THE GRID IS PLACED IN BETWEEN PATIENT AND THE FILM/DETECTOR
CONSTRUCTION OF GRID:
 GRID ARE MADE UP OF THIN LEAD STRIPS SEPERATED BY INTERSPACING MATERIAL.
 THE INTERSPACING MATERIAL IS USUALLY MADE UP OF ORGANIC
COMPOUND (CARBON BASEED).
 OR ALUMINIUM WHICH HAS LOW ATOMIC NUMBER.
 THIS WHOLE THING IS COVERED BY ALUMINIUM
ENVELOPE.

FUNCTION OR WORKING OF GRID:
THE WORKING OF GRID US EXPLAINED BY THE FIGURE
1. MOST OF THE PRIMARY RAY , LIKE RAY1,PASS THROUGH THE INTERSPACING MATERIAL
TO REACH FILM TO PRODUCE IMAGE
2.MOST OF THE SCATTERED RADIATION LIKE RAY 2 TRAVEL OBLIQUELY TO THE LEAD STRIP
AND ABSORBED BY THE LEAD STRIP
3.SOME OF THE PRIMARY RAY LIKE RAY 3 ARE ABSORED BY THE LEAD STRIP TO PRODUCE
WHITE LINE IN THE IMAGE BUT , THESE WHITE LINES ARE NOT SEEN BECAUSE THE LEAD
STRIP ARE SO THIN AND CLOSE TO EACH OTHER
4. SOME OH THE SCATTERED RAY LIKE RAY 4 WITH THIS SMALL ANGLE OF SCATTER ARE
PAREALLEL TO THE LEAD STRIP ARE NOT ABSORBED BY THE LEAD STRIP . THEY PASS
THROUGH THE INTERSPACING MATERIAL TO REACH THE FILM

 BUT THE GRID CUT OFF 80 TO 90 % OF SCATTERED RADIATION REACHING THE FILM
AND THERE BY INCREASES THE CONTRAST OF THE IMAGE
GRID CHARACTERISTICS:
SOME OF THE IMPORTANT CHARACTERISTICS OF THE GRID ARE DISCUSED BELOW;
1.GRID RATIO:
 GRID RATIO IS THE RATIO OF THE HEIGHT OF THE INTERSPACING MATERIAL TO
ITS WIDTH BETWEEN TWO LEAD STRIPS
GRID RATIO = h/d
AS GRID RATIO INCREASES , THE GRID REMOVES MORE SCATTERED RADIATION, THE
TYPICAL GRID RATIO RANGES FROM 4:1 TO 16:1

2. GRID FREQUENCY:
 IT IS DIFINED AS THE NUMBER OF LEAD LINES PER cm OR inch.
 THE GRID FREQUENCY RANGES FROM 25 TO 60 LEAD LINES PER cm
 IF THERE ARE MORE LEAD LINES , IT IS CALLED FINE GRID
 IF THERE ARE LESS LEAD LINES , IT IS CALLED COARSE GRID
3.CONTRAST IMPROVEMENT FACTOR:
 IF THE GRID IS USED THE CONTRAST IS IMPROVED .
 CIF IS DEFINED AS THE RATIO OF IMAGE CONTRAST WITH GRID TO IMAGE
CONTRAST WITHOUT GRID
CIF= IMAGE CONTRAST WITH GRID
IMAGE CONTRAST WITHOUT GRID
4. GRID FACTOR OR BUCKY FACTOR:
 GRID FACTOR IS DEFINED AS THE RATIO OF X-RAY EXPOSURE WITH GRID T
X-RAY EXPOSURE WITHOUT GRID

GRID FACTOR = X-RAY EXPOSURE WITH GRID
X-RAY EXPOSURE WITHOUT GRID
TYPES OF GRID:
THERE ARE DIFFERENT TYPES OF GRID USED IN RADIOLOGY .
THEY ARE:
1. PARALLEL GRID
2. FOCUSSED GRID
3. PSUDOFOCUSSED GRID STATIONARY GRID
4. CROSSED GRID
5. MOVING GRID (BUCKY)
PARALLEL GRID:
 IN PARALLEL GRID , THE LEAD STRIPS ARE PARALLEL TO EACH OTHER
 IT IS EASY TO MANUFACTURE BUT IT PRODUCE GRID CUT OFF
 SINCE X-RAY BEAM IS DIVERGENT , THE PRIMARY X-RAY OF THE EDGES
TRAVEL OBLIQUELY TO YHE LEAD STRIP
 AND ARE ABSOBED BY THE LEAD STRIP THIS IS CALLED “GRID CUT OFF”

 WHEN THE GRID RATIO INCREASES , GRID CUT OFF INCREASES
FOCUSSED GRID:
 IN FOCUSSEDD GRID , THE LEAD STRIP ARE ARRANGED SUCH THAT , THEY FOCUS AT
PARTICULAR DIATANCE
 THIS DESIGN IS TO AVOID GRID CUT OFF
 THE FOCUS GRID DESIGNED FOR PARTICULAR FOCUS CAN BE USED FOR A RANGE OF
FOCUS
 IF FFD (FILM TO FOCUS DISTANCE) IS MORE THAN THE RANGE , THEN THERE WILL BE
GRID CUT OFF
 IN FOCUS GRID THE CENTRAL AXIS OF X-RAY , SHOULD PASS THROUGH THE CENTRE OF
THE GRID
 THE DISADVENTAGE OF FOCUSSED GRID IS, IT IS DIFFICULT TO MANUFACTURE

PSEUDOFOCUSSED GRID:
 IN THIS , THE THICKNESS OF THE LEAD STIP DECREASES FROM CENTRE TO EDGE
 THIS DESIGN IS TO PREVENT GRID CUT OFF AT THE EDGES
 BUT THE CONTRAST IMPROVEMENT WILL BE HIGHER IN THE CENTER AND REDUCES
FROM CENTER TO EDGE
CROSSED GRID:
 THE SCATTERED X-RAY BEAM TRAVELLING PARALLEL TO THE LEAD STRIP WILL NOT
BE ABSORBED BY PARALLEL GRID OR FOCAL GRID
 IN ORDER TO ABSORB THIS SCATTERED RADIATION , CROSSED GRIF ARE USED
 CROSSED GRID IS TWO PARALLEL GRID PLACED ONE THE OTHER SO THAT , THE LEAD
STRIP ARE PERPENDICULAR TO EACH OTHER (CROSSED)
 IT EFFECTIVELY ABSOR SCATTERED X-RAY IN ANY DIRECTION.
 THE DISADVANTAGE OF CEOSSED GRID IS , THE X-RAY BEAM SHOULD FALL
PERPENDICULAR TO THE GRID AND IF THE BEAM IS ANGULATED , IT WILL ABSORB
THE PRIMARY BEAM

MOVING GRID (POTTER – BUCKY):
 THE DESIGN OF STATIONARY FINE GRID IS DIFFICULT TO MANUFACTURE
 SO INSTEAD OF FINE , COARSE GRID IS USED
 IN COARSE GRID THE LEAD STRIP ARE THICK AND ARE SEPERATED BY LARGE DIATANCE
 BUT , IF THE COARESE GRID IS USED , THE GRID LINES ARE SEEN IN THE RADIOGRAPH
 HENCE , THE COARE GRID IS MOVED PERPENDICULAR TO THE LEAD STRIP TO AND
DUEING X-RAY EXPOSURE
 THE MOVING COARSE GRID IS EQUIVALENT TO FINE GRID
 GENERALLY , THE BUCKY IS PLACED BETWEEN PATIENT AND THE FILM
 THE GRID SHOULD MOVE AT LEAST 2-3 Cm ON EITHER SIDE
 THE SPEED OF GRID MOVEMENT IS SUCH THAT , IT BLURS THE GRID LINE IN
THE RADIOGRAPH
 GENERALLY , THE GRID STARTS TO MOVE , WHEN THE STAND BY SWITCH IS PRESSED
BEFORE EXPOSURE AND GRID MOVEMENT SHOULD BE STOPPED AFTER THE EXPOSURE
IS OVER
 THERE ARE 3 TYPES OF GRID MOVEMENT:
i. SINGLE STROKE MOVEMENT
ii. OSCILLATING MOVEMENT
iii. RECIPROCATING MOVEMENT

SINGLE STROKE MOVEMENT:
 IN THIS , THE GRID IS ATTACHED TO THE WOUND SPRING
 BEFORE EXPOSURE , THE WOUND SPRING IS TIGHTENED SO THAT THE GRID
MOVES WITH A SPRING ACTION
 THE SPEED OF GRID MOVEMENT DECREASES WITH TIME
 THE EXPOSURE SHOULD STOP , BEFORE THE GRID MOVEMENT STOP.
OSCILLATING MOVEMENT:
 IN THIS , THE GRID IS PLACED IN BETWEEN 2 PAIR OF ELECTROMAGNETES
 THE ELECTROMAGANETS 1 AND 2 ARE ACTIVATED ALTERNATIVELY BY APPLYING
THE CURRENT TO THE MAGNETS 1 AND 2 ALTERNATIVELY
 THE GRID OSCILLATE IN BETWEEN THE ELECTROMAGANET
 THE SPEED OF GRID MOVEMENT IS AS SHOWN IN FIGURE

RECIPROCATING MOVEMENT:
 IN THIS , THE SPEED OF GRID MOVEMENT IS FAST IN ONE DIRECTION AND RETURNS
SLOWLY IN OTHER DIRECTION
 THE SPEED OF GRID MOVEMENT IS AS SHOWN IN FIGURE

THE END
REFERRED BY:
THAYALAN SIR
-BOOK AND
CHRISTENSEN’S BOOK

X-RAY GRID BUCKY

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