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45 Cards in this Set
- Front
- Back
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what are the 3 prime factors under direct control of the radiographer? |
mAs .. miliampreage/second kVp .. kilovoltage Distance |
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Describe Quantity |
number of x-ray photons in the beam |
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what is quantity also referred to as? |
intensity, x-ray output, exposure |
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how is quantity measured? |
Roentgens or Gray |
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what affects Quantity? |
mAs, kVp, distance, and filtration. |
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Define quality |
measurement of the penetrating ability of the x-ray beam |
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what is quality affected by? |
kvp, filtration |
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what is the primary controller or quantity? |
mAs
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what is the primary controller of quality |
kVp |
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what is mA the measurement of? |
tube current. the number of electrons crossing the tube per second |
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if you increase the mA what happens to the number of electrons corssing the tube and hitting the target? |
increase |
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mA is ___________ to e- in the tube (tube current) |
directly proportional |
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define mAs |
the product of the number of e- crossing the tube and the length of time |
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mAs is ______ to quantity |
directly proportional |
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define density |
degree of blackening |
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_____ is the primary controller of density |
mAs |
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if you double the mAs you ____ the density |
double |
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kVp controls the _______ and _____ of th electrons crossing the tube |
speed and energy |
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Kvp primarily effect quantity or quality? |
quality |
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kVp has a _________ relationship to quantity and quality |
direct |
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True/False: changes in kVp will impact density |
true |
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if we increase the quantity of the photons what will it do to the density? |
increase |
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_____ is the primary controller of contrast |
kVp |
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Define contrast |
black and white |
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what does high contrast look like |
very black and white |
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what does low contrast look like |
many many shades of gray |
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if we increase kVp by 15% what will it cause in the exposure? |
doubling |
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If we increase the kVp by 15% we must ____ the mAs by ____. |
decrease the mAs by half |
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______ is the primary controller or density |
mAs |
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_____ is the primary controller of contrast |
kVp |
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Intensity is measured in .. |
roentgens (R) |
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distance has an ____ relationship with exposure |
inverse |
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why does distance have an inverse relationship with exposure? |
farther from the source the lower the quantity of photons within the area.
think of a flashlight .. the farther away it is, the less intense the light is. |
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what equation is used for the inverse square law |
I 1 D2^2 ___ = ______ I2 D1^2
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increase the distance = ______ intensity of the beam |
decrease |
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decrease distance = _____ intensity of the beam |
increase |
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doubling of distance = ___ the intensity |
1/4 |
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halving the distance = ___ the intensity |
4x |
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what is the exposure maintenance formula or the direct square law formula? |
mAs1 D1^2 _____ = ______ mAs 2 D2^2 |
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more distance = ____ mAs |
more |
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if you are going to adjust kVp, for an exam that is over-exposed you would |
decrease the kVp by 15%
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if you are going to adjust kVp, for an exma that is under-exposed you would |
increase kVp by 15% |
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an exam that is under-exposed what would you do to the mAs? |
double |
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an exam that is over-exposued what would you do to the mAs? |
halving |
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if you double the distance, the exposure at the IR will be _____. |
reduced by 1/4 |
