X-RAY GRID BUCKY

This slide is very use full for study purpose

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

2. 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 ENVELO PE.

3. FUNCTION OR WORKING OF GRID: THE WORKING OF GRID US EXPLAINED BY THE FIGURE 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

4. 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

5. 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 TO X-RAY EXPOSURE WITHOUT GRID

6. 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: PARALLEL GRID FOCUSSED GRID PSUDOFOCUSSED GRID STATIONARY GRID CROSSED GRID MOVING GRID (BUCKY) PARALLEL GRID: IN PARALLEL GRID , THE LEAD STRIPS ARE PARALLEL TO EACH OTHER I T 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”

7. 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

8. 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

9. 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: SINGLE STROKE MOVEMENT OSCILLATING MOVEMENT RECIPROCATING MOVEMENT

10. 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

11. 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

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