Ch12: Grids

Question 1

What are the benefits of a grid?

Answer 1

Cleans up scatter
Improves contrast

Question 2

Where is the grid located?

Answer 2

Between patient and IR in/above Bucky

Question 3

Define grid ratio

Answer 3

Height of lead strips / interspace width
H/D

Question 4

Define grid frequency

Answer 4

of lead strips per unit length
Most common is 85-103 lines/inch

Question 5

What is a grid pattern?

Question 6

List the different grid patterns

Answer 6

Linear - parallel or focused
Cross hatch

Question 7

List the grid conversion factors

Question 8

Why would you use a grid conversion factor?

Answer 8

to determine how you need to adjust technique to avoid overexposure/maintain good EI when adding/removing a grid

Question 9

List the different grid errors

Question 10

How do grids improve contrast?

Answer 10

By cleaning up scatter before it hits IR

Question 11

When would you use a grid?

Answer 11

Thicker body parts (more than 4in)
KVP over 60

Question 12

What is a grid made of?

Answer 12

Vertically placed lead strips with interspace material in between (usually made of aluminum)

Question 13

Why is it important to know the direction the lead strips are running in a grid?

Answer 13

So you know which direction to angle so you don’t angle the beam into the strips

Question 14

Why do grids vibrate/move?

Answer 14

to blur the lead strips in the grid so they don’t show up on the image