It's all about the grid and Types of grid

1. ZAID BIN HASSAN

2. GRIDS
INVENTED BY
DR. GUSTAV
BUCKY
IN THE YEAR
1913
Bucky’s Original Grid

3. GRIDS :
• Consist of a series of lead foil
strips
• Separated by x-ray-transparent
spacers
• Remove scatter radiation from
large radiographic fields

4. SCATTER
• Scatter radiation arises from many
points within the pt. & is
multidirectional ,so most of it is
absorbed by the lead strips & only a
small amt. passes between them

5. GRIDS DO NOT REDUCE THE
AMOUNT OF SCATTER
RADIATION REACHING THE
IMAGING PERSONNEL
GRIDS DO INCREASE
RADIATION EXPOSURE OF
PATIENTS

6. GRIDS STRIPS ARE MADE OF
LEAD (Pb)
LEAD HAS HIGH Z#
AND ABSORBS SCATTER
RADIATION THROUGH
PHOTOELECTRIC
INTERACTION

7. Grid Interspaces:
Filled with aluminium or organic
compounds
• Support the thin lead foil strips
Aluminium
• Manufactured precisely
• Structurally stronger
• Absorbs more of the 1o radiation in
higher patient exposure
• Better contrast improvement

8. Grid ratio
 Ratio of height of lead strips and
the distance b/w them.
G.R. = h/D
 Express grid’s ability to remove
scatter radiation
 Usually ranges from 4:1 to 16:1
 Higher the ratio; better the grid
function.
 G. R. is indicated at the top of
the grid by manufacturers.

9. GRID RADIOGRAPHY IS
RECOMMENDED FOR:
• 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

10. GRID PATTERN
Orientation of lead strips in their
longitudinal axis,
Two basic patterns are-
1. Linear grids
2. Crossed grids

11. Linear Grid
• Strips parallel to
each
other in the
longitudinal axis
• Allow angulation of
tube
along length of grid
• Crossed Grid
• 2 superimposed
linear grids
• Same focusing
distance
• Cannot be used for
oblique /angulation
techniques

12. GRID TYPES
• STATIONARY
1) PARALLEL
2) CROSSHATCH
3) FOCUSED
• MOVING - SINGLE STROKE & RECIPROCATING

13. Stationary grids
• 60 – 110 lines per inch.
ADVANTAGE –
Improve radiographic contrast.
DISADVANTAGE –
Lead strips cast shadows on the radiograph as thin lines.

14. Parallel Grid
• Lead strips parallel to each
other
• Strips are never aligned
with primary beam since
all are vertical (except for
strips directly under
central ray)
• Used in fluoroscopic spot
film devices.

15. Cross Grid (cross hatch)
• 2 grids on top of each other with lead strips of one
perpendicular to other

16. FOCUSED GRID
• Lead strips are angled slightly; so
that they focus in space.
Linear focused grid:
converge at a line
space convergent line
Crossed focused grid:
converge at a point in

17. MOVING GRID
• Dr. Hollis Potter in 1920 used moving grid ; and
named it as
• – BUCKY DIAPHRAGM
• Most of the moving grids are focused.
ADVANTAGE –
Removal of more scattered radiation
Removal of grid lines in IR

18. Moving grid : Potter-Bucky grid
• The movements of the grid blurs out the
shadow of the lead strips
• Starts moving when x-ray tube begins to
rotate
• Eliminates grid-lines from the film

19. • To avoid grid lines :
• grid must move fast enough to cause blurring of
the lead strip
- too slow  random density variations
grid lines visible
• Transverse motion of grid must be synchronous
with the pulses of the x-ray generator
- causes shadows to be superimposed on the
shadow of its neighbour
*1-3 cm back & forth movement

20. • Disadvantage:
• Costly
• Fault will result in vibration of the whole x-
ray table
• Limit the minimum exposure time
• Increases patient exposure

21. P-B DIAPHRAGM

22. • Reduce scatter radiation in two direction as
they have crossed grid alignment.
• It has copper as grid strip material and air
for the interspaces.
• Results in 3.8:1 ratio.
• Not used in magnification mammography
where the scattered radiation is removed by
air gap.