RSAP 180 Learning Outcome #6 Review

What is the purpose of a radiographic grid?

• A device used to improve the contrast on an X-ray image

• Allows for a small effective focal spot size to be achieved

• Stops a radiation exposure at a predetermined time

• Increases incoming line voltage

True or False: A grid should be used when imaging thicker body parts and when using high kVp techniques

• True

• False

Answer explanation

When the body part exceeds 10cm

When the kVp is above 60 kVp

The grid ratio is the ratio of the:

• Height of the plastic strips to the width of the plastic strips

• Height of the lead strips to the distance between the lead strips

• Height of the lead strips to the width of the lead strips

• Thickness of the grid to the width of the cassette

When a grid with a higher grid ratio is used, the radiation dose to the patient will ______ and the radiographic contrast will ________.

• Increase; decrease

• Increase; increase

• Decrease; increase

• Decrease; decrease

What is the grid ratio of a grid with strips that are 4 mm in height and spaced 0.5 mm apart?

Grid Ratio  = h/D

• 16:1

• 12:1

• 8:1

• 5:1

Answer explanation

4mm/0.5mm  = 8:1 grid

How does grid ratio affect scatter absorption?

• The lower the grid ratio, the greater scatter absorption

• Grid ratio has no affect on scatter absorption

• The higher the grid ratio, the less scatter absorption

• The higher the grid ratio, the greater scatter absorption

The bucky factor:

• Indicates how much contrast will increase when comparing non-grid and grid exposures

• Indicates how fast the grid is moving

• Indicates how much mAs must be increased compared to non grid techniques

• Indicates how much scatter radiation is present

A _________ grid has central grid strips that run parallel and as the strips move away from the central axis, they become more and more inclined.

• Focused

• Cross Hatched

• Parallel

• Horizontal

The distance (SID) within which the grid can be used without a significant loss of primary radiation is called __________.

• Grid frequency

• Focal Range

• Grid Ratio

• Bucky Factor

The number of grid strips or grid lines per inch or centimeter is called ________.

• Grid Ratio

• Grid Frequency

• Line Pair

• Line Focus Principle