Grids Flashcards
Three things happen when the beam passes through the body
- Pass through unaffected
- Be absorbed
- Interact and change direction (scatter)
Which interaction is caused by scatter?
Compton interaction
Increasing kVp, ________ Compton interactions.
Increases
Interactions with the IR from scatter radiation will be of no
Diagnostic value
What controls the quantity of scatter produced?
The patient
The amount of scatter radiation _________ with increase in patient thickness, larger field sizes, and _________ with higher atomic number tissues/parts
Increases
Decreases
Thin, flat, rectangular device made by placing a series of radiopaque lead strips side by side and separating the strips by an interspace material that is radiolucent
Grids
The lead strips are very thin _____ and the interspace material is thicker and made of ______.
Aluminum
When should you use a grid?
Body part thickness exceeds 10cm
kVp is above 60
When was the grid invented and who invented it?
1913
Gustav Bucky
The lead strips are
Radiopaque
The radiopaque strips are made of
Lead
The interspace strips are
Radiolucent
What are the interspace strips made of
Aluminum of plastic fiber
The function of the grid involves the selection of
Material
Grid ratio
Grid frequency
the ratio of the height of the lead strips to the distance between the strips
Grid ratio
What is the grid ratio formula?
H/distance
_____ grid radios allow less scatter radiation to pass through to the IR
Higher
Number of grid lines per inch or centimeter
Grid frequency
By combining the info from grid ratio and grid frequency, the radiographer can determine the total _____ of lead in a grid.
Quantity
Grids with higher grid frequency have _______ lead strips
Thinner
______ content of the grid is what determines the grid’s efficiency at cleaning up scatter and improving contrast.
Lead
Lead strips running in only one direction
Linear grids
Lead lines running at right angles to one another
Criss-crossed or cross hatched grids
Linear grids are most common due to
Tube angulation
Angulation across the long axis would result in the beam hitting the lead strip and getting absorbed. This is known as _______.
Grid cutoff
Lead and interspace material run parallel to one another
Parallel grid
Lead lines are angled to match the angle of divergence of the primary beam
Focused grid
If the lines of a focused grid were extended, the strips would intersect along a line in space known as ________
Convergence line
________ grids also allow more transmitted photons to reach the IR
Focused
Parallel grids are best used with ____ SID’s.
Long
