1. Chapter 6, Fauber Supplement-Chapter 14, Bushong
SCATTER AND GRIDS
Chapter 6, Fauber
Supplement-Chapter 14, Bushong

2. REVIEW:MATTER OR TUBE INTERACTION?
Bremsstrahling
Characteristic
Coherent
Compton
Exit/remnant
Infrared
Photoelectric

3. Scatter Which interaction causes scatter?
What factors increase scatter?
If low kVp is used, what type of matter interaction increases?

4. REDUCING SCATTER Beam restriction
Collimation – as collimation increases what happens to patient’s dose?
Collimation – as collimation increases what happens to the production of scatter?
Collimation- as collimation increases what happens to the scale of contrast- shorter or longer?

5. Beam restricting devices
Aperture diaphragms
“hole”
Cones/Cylinders
Collimators
Two sets of adjustable lead shutters (pg 144)
PBL

6. REVIEW INHERENT FILTRATION? ADDED FILTRATION?
BY LAW, MINIMUM AMOUNT OF FILTRATION?
LONG SCALE CONTRAST AND SCATTER- IS THERE A RELATIONSHIP?

7. GRID
1913 Dr.Gustave Bucky.
1/4 inch thick and range from 8 x10 to 17 x17
Lead strips separated by interspaces
Center line directs the radiographer as to which way the lines are running.

8. WHEN TO USE A GRID Pt thickness kVp chosen (some argument here!!!)
What exactly does a grid do?
(see pg 147)
Absorbs scatter while allowing primary radiation to pass through

9. GRID CONSTRUCTION INTERSPACE MATERIAL GRID FREQUENCY MADE FROM?
Higher the Frequency, the thinner the interspace material
GRID RATIO
RATIO OF HEIGHT OF LEAD STRIPS TO THE DISTANCE BETWEEN THEM h/D
HIGHER THE RATIO, THE THE FREQUENCY
WATCH OUT FOR TESTING TRICKS- THE THICKNESS OF THE LEAD IS NOT USED TO CALCULATE GRID RATIO.

10. GRID PATTERNS Linear Cross or cross hatched
Parallel or non-focused grid
Focused grid
Focal distance and convergent point
Recommended SID
Wafer grid/grid cassette/grid cap

11. STATIONARY VS RECIPROCATING GRIDS
Potter Bucky diaphragm

12. Grid Conversion See page 154, table 6-2 Add 10:1 Bucky Factor/GCF = 5
Let’s discuss an easier way to increasing grid ratio and missing factor

13. GRID BOO BOOS Grid cut-off –FOUR TYPES
Upside down focused grid boo boo
Off level grid boo boo
Off center grid boo boo
Off focus grid boo boo

14. GRID BOO BOOS Grid cut-off -4 TYPES Upside down focused grid boo boo
Off level grid boo boo
Off center grid boo boo
Off focus grid boo boo
Loss of density, edges
Over all reduction of density
Loss of density, periphery

15. A typical grid is or has Linear Why? Focussed Why? Mid ratio Why?
Focal range of 40 or 72 inches Why?

16. AIR GAP (Works like a grid)
Increased OID
Less scatter reaching IR
Why is this limited in its usefulness?