Rules Flashcards
How do you adjust the radiograph if it’s too dark but the structures are visible?
Decrease kV 15% OR decrease mAs 50% (50% mAs rule)
How do you adjust the radiograph if it’s too light and the structures are visible?
Increase kV 15% OR increase mAs 2x
How do you adjust the radiograph if it’s too dark and the structures are not visible?
Decrease kV 15% AND increase mAs 50% (50% mAs rule)
Optimal kV range for cervical spine?
75-85 kV
Optimal kV range for AP thoracic?
75-85 kV
Optimal kV range for lateral thoracic?
85-95 kV
Optimal kV range for AP lumbar?
80-90 kV
Optimal kV range for lateral lumbar?
85-95 kV
Optimal range for AP full spine?
80-100 kV
Optimal kV range for pelvis/hip?
75-85 kV
What’s the significance of mAs?
It controls film density
What is the reciprocal rule?
Doubling the mAs doubles density of the film
What increases the density of the film 2x?
Increase kV 15%
What cuts the film density in half?
Decrease kV 15%
High contrast is also known as…
Short scale (black/white with few shades of gray)
Low contrast is also known as…
Long scale (many shades of gray)
If film is too dark or light but still shows structures…
Use 15% rule
If film is too gray but density is good…
Decrease kV 15% AND double mAs
If film does not have enough gray but density is good…
Increase kV 15% AND cut mAs 50%
How do you adjust the radiograph if it’s too light and the structures are not visible?
Increase kV 15% AND increase mAs 2x
If density is good but film does not have enough gray…
Increase kV 15% and decrease mAs 50%
If density of the film is good but is too gray…
Decrease kV 15% AND increase mAs 2x
In order to make a long scale film (gray) look like a short scale film…
Decrease kV 15% and increase MAs 2x (double it)
Underexposed versus long scale…
Underexposed is too light and fuzzy
Overexposed versus long scale…
Overexposed is splotchy, some parts are too white and some too dark
Slight change, if film is slightly too dark compared to slightly lighter film…
Darker film has 30% more mAs
Lighter film has 30% less mAs
*30% rule
What two densities make up the Cornu of the thyroid cartilage (on lateral cervical)
Water
Calcium
How do we make the film look better if its gray and fuzzy? (Kvp is set at 80 for cervical)
Double mAs
What is dark on the ilia on an AP pelvic? What natural densities makes it up?
Gas/air
Air makes it up
Why do we see rib cartilages?
Water and natural metal
In order to make a short scale film look like a long scale film…
Increase kV 15% AND cut mAs 50%
