Card Set Information
Scatter is caused by what type of introduction?
Scatter does what 2 things to the film?
Adds unwanted density
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