# exposures

The flashcards below were created by user acmolt on FreezingBlue Flashcards.

1. Scatter is caused by what type of introduction?
Compton
2. Scatter does what 2 things to the film?
• decrease contrast
3. T or F: Fog always decreases Contrast
True
4. Patient thickness and large open field size increase what?
Scatter
5. Where is the Grid located?
between the patient and the film
6. When should you use a grid? 2 things
• parts greater that 10 cm
• Kvp above 60
7. Describe a grid..
• thing flat rectangular device
8. Who invented the Bucky and Explain it?
• Dr. Gustav Bucky
• Lead strips in checker board appearance
9. Describe Hollis Potters improvement to the Bucky?
• Lead strip run in the 1 direction
• strips move to blur during exposure
10. What are Strips like located with the grid?
Converted in foil, making them absorb more scatter because of high atomic number
11. interspace material allows_______photons to pass through?
Primary
12. The ratio of height of lead strips to the distance b/w them is_______
grid ratio
13. high grid ration= more or less scatter clean up?
more
14. How does the beam have to be for it to get through a grid with high ratio?
pretty darn straight
15. With a longer distance you want low grid ratio? T or F
True
16. Number of lead strips per inch is?
Grid frequency
17. the higher the frequency the thicker the lead strips? T or F
F * Thinner
18. The most common Grid frequency used is?
85 - 103
19. what is total lead content? and how is it measured?
• amount of lead in grid
• mAs per unit area= g/cm2
20. what is the most important factor in determining scatter clean up?
21. General Rules
• Grids with high grid ration (close strips)
• Grids with lower frequency (thicker)
22. what are the two types of grid ratio?
• linear
• criss cross/cross hatched
23. linear is the most common grid pattern? T or F
True.. can never angle against strips
24. can you angle the tube with a criss cross grid?
No, will = grid cut off
25. what is grid cut off
loss of density with in the film
26. Describe a parallel grid
• strips that run up and down will never touch
• longer SIDS= angle never strikes strips
27. Where do the angled strips meet in a focused grid in space ?
convergence line
28. with a focused grid, is there more/less room for error and why?
less, bc less latitude (less space b/w)
29. The Bucky is a _______Grid?
reciprocating
30. the bucky moves the lead strips perpendicular to the way they run? T or F
True
31. in the table and upright Bucky do the strips run lengthwise or crosswise?
Lenghthwise
32. when using a grid, higher kvp or mAs?
mAs
33. what is GCF and what is the formula?
• Grid Conversion factor
• GCF= mAs1/mAs2 = GCF1/GCF2
34. 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
35. 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
 Author: acmolt ID: 8177 Card Set: exposures Updated: 2010-02-26 04:39:53 Tags: ch 18 Folders: Description: exposures Show Answers: