5. Radiographic grids and anti scatter grids

Question 1

What is Compton scatter?

Answer 1

When the primary beam interacts with electrons in the body and causes photons to change position

Question 2

What would a higher grid ratio do to scatter?

Answer 2

It would decrease the scatter reaching the IR

Question 3

How much scatter radiation do grids reduce to the IR

Answer 3

85-97%

Question 4

What would increasing the height and decreasing the width demonstrate in a grid?

Answer 4

A higher grid ratio

Question 5

What is grid frequency? What is the unit?

Answer 5

It is the # of grid strips or lines per cm (pb)-there’s 25-45 grid strips/cm

Question 6

What is the contrast improvement factor? What is it usually stated with?

Answer 6

How much the grid increases the contrast on average, stated with either kVp, patient thickness or field size

Question 7

What 3 factors does the contrast improvement factor depend on?

Answer 7

1. kVp
2. Patient thickness
3. Field size

Question 8

What is the bucky factor?

Answer 8

It tells us how much of an increase in technique will be required for a particular exposure compared to a non grid exposure.

Question 9

What prime factor do we have to change when using grids?

Answer 9

mAs

Question 10

What is the grid ratio when there’s no grid?

Answer 10

1

Question 11

What is the grid ratio when using a 5:1 grid

Answer 11

2

Question 12

What is the grid ratio when using a 6:1 grid

Answer 12

3

Question 13

What is the grid ratio when using a 8:1 grid?

Answer 13

4

Question 14

What is the grid ratio when using a 12:1 grid?

Answer 14

5

Question 15

What is the grid ratio when using a 16:1 grid?

Answer 15

6

Question 16

What are the 4 grid types?

Answer 16

1. Linear parallel
2. Crossed
3. Linear focused
4. Crossed focused

Question 17

What are the pros and cons of linear focused grids?

Answer 17

Pros: loosing less good radiation
Cons: Have to centre in the middle of IR

Question 18

What are the pros and cons of linear parallel grids?

Answer 18

Pros: Can center anywhere on IR
Cons: Loosing more good radiation at the peripheries

Question 19

What is grid cut off?

What is it caused by?

Answer 19

An undesirable absorption of primary x-ray beams by grid strips, which prevents the useful x-rays from reaching the image receptor. Caused by grid errors or not being in detent

Question 20

What are the benefits to grid line suppression software?

Answer 20

You only have to use a low grid ratio, and do not have to use a higher technique