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Scatter is caused by what type of introduction?
Scatter does what 2 things to the film?
- Adds unwanted density
- decrease contrast
T or F: Fog always decreases Contrast
Patient thickness and large open field size increase what?
Where is the Grid located?
between the patient and the film
When should you use a grid? 2 things
- parts greater that 10 cm
- Kvp above 60
Describe a grid..
- thing flat rectangular device
- contains lead strips separated by radiolucent enter space material
Who invented the Bucky and Explain it?
- Dr. Gustav Bucky
- Lead strips in checker board appearance
Describe Hollis Potters improvement to the Bucky?
- Lead strip run in the 1 direction
- strips move to blur during exposure
What are Strips like located with the grid?
Converted in foil, making them absorb more scatter because of high atomic number
interspace material allows_______photons to pass through?
The ratio of height of lead strips to the distance b/w them is_______
high grid ration= more or less scatter clean up?
How does the beam have to be for it to get through a grid with high ratio?
pretty darn straight
With a longer distance you want low grid ratio? T or F
Number of lead strips per inch is?
the higher the frequency the thicker the lead strips? T or F
F * Thinner
The most common Grid frequency used is?
85 - 103
what is total lead content? and how is it measured?
- amount of lead in grid
- mAs per unit area= g/cm2
what is the most important factor in determining scatter clean up?
- Grids with high grid ration (close strips)
- Grids with lower frequency (thicker)
what are the two types of grid ratio?
- criss cross/cross hatched
linear is the most common grid pattern? T or F
True.. can never angle against strips
can you angle the tube with a criss cross grid?
No, will = grid cut off
what is grid cut off
loss of density with in the film
Describe a parallel grid
- strips that run up and down will never touch
- longer SIDS= angle never strikes strips
Where do the angled strips meet in a focused grid in space ?
with a focused grid, is there more/less room for error and why?
less, bc less latitude (less space b/w)
The Bucky is a _______Grid?
the bucky moves the lead strips perpendicular to the way they run? T or F
in the table and upright Bucky do the strips run lengthwise or crosswise?
when using a grid, higher kvp or mAs?
what is GCF and what is the formula?
- Grid Conversion factor
- GCF= mAs1/mAs2 = GCF1/GCF2
What are the four Rules of Grids?
- 1) tube properly aligned to tube
- 2) correct focal range
- 3) correct angle with strips
- 4) tube side of Grid, facing the grid
What are 4 types of Grid errors and with what type of grid do they occur?
- off level- focused and parallel
- off center- focused
- off focus-focused
- upside down-focused
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