LECTURE II HIGH YIELD Flashcards
intensity of the x-ray beam is measured how?
quantity x quality
wha is the unit of the x-ray beam? what is the unit of this?
roentgen
coulombs/kg
what are the 4 factors that affect quantity of x-ray beam photons?
millamperage x time (mAs)
kilovoltage (kVp)
distance
filtration
this is the most common thing to tweak when changing x-ray beams
*this is a factor affecting quantity of x-ray beam photons
millamperage x time (mAs)
what is the affect of increasing mAs?
what is this directly proportional too?
it increases the area under the Bremsstrahlung curve, so it doubles the amount of x-rays and efficacy in breaking through structures, this increase in area doesn’t change energy distribution
beam intensity so:
2 mAs = 2 X-rays emission
what is the affect of increasing kVp?
increases beam intensity four-fold
so 2 x kVp=4 x X-ray emission
what is the 15% pulse in relation to the kVp?
maintains constant film density and accompanied by a decrease in mAs by 50%
so increase in kVp by 15% means, decrease in mAs by 50%
how does kVp affect film blackening? and affect of blackening?
film gets darker with increased radiation
the effect is equal to the 4th power
how is distance related to the radiation intensity of the x-ray beam intensity?
via inverse square law where the radiation intensity varies inversely with distance squared from the source
so 2 x distance means, 4 x the beam divergence
what is the effect of increasing filtration?
what shift direction is safer for patients?
decreases the area under the curve (x-ray intensity/emission) or attenuates it to increase effective beam energy
shift to the right, so the higher the atomic number the safer
what is the quality of x-ray beam photons affected by?
kVp and filtration as well
what is the meaning of a low HVL? what increases this? and what does this increase mean?
too many low energy photons
filtration
increases beam quality
how are kVp and HVL related?
at a certain kVp, a certain HVL or thickness of Al is important for safety
