Image Quality Control--Quiz 2 Flashcards
What does changing the mAs alter? How does it do this?
alters film DENSITY
by directly changing number of ELECTRONS and therefore photons
What does changing the kVp do to the image? How?
changes CONTRAST
makes image darker–> b/c more x-rays pass through the patient and more are created
Does kVp or mAs alter density of the film?
mAs
Does kVp or mAs alter contrast of the film?
kVp
How does a higher kVp alter the contrast of the film?
lower contrast higher gray scale)
How does a lower kVp alter the contrast of the film?
higher contrast (lower gray scale)
On a good film, when we are looking at a bone, what should we be able to tell the difference between?
the cortical bone and the trabecular bone
What do we have an issue with if we cannot tell the difference between cortical bone and trabecular bone?
have a kVp problem
If we cannot tell the difference between cortical and trabecular bone, and the image is white and chalky, what must we do?
increase kVp by 15%
in order to decrease contrast
If we cannot tell the difference between cortical and trabecular bone, and the image is foggy, gray, hazy, and smoky, what must we do?
decrease kVp by 15%
in order to increase contrast
On a good film, when we look at trabecular bone, what should we “see”, what about for soft tissue?
should be able to see “through” trabecular bone, but still see soft tissue shadow
What if on a film we cannot see through overlapping bones? What should we do?
underexposed
need to double mAs
What if on a film we can’t see soft tissues? What should we do?
overexposed
need to halve mAs
What is the mAs rule?
2x Reciprocal Rule (Doubling Rule)
2x mAs = 2x density
1/2 mAs = 1/2 density
What is the rule if we want to change kVp?
15% change rule to kVp
BUT if we increase kVp, we must decrease mAs by 1/2
if we decrease kVp, we must increase mAs by 1/2
