Milliamperes / Time Flashcards
Milliamperes (mA)
controls the current flow to the cathode filament at the time of exposure
As mA is __________, filament temperature rises increasing the number of electrons released through ____________.
- increased
- thermionic emission
An increase in mA will _______ the number of x-ray photons in the primary beam (quantity)
increase
A doubling of mA will _________ radiographic density
double
The relationship of mA selected and overall image density is __________
directlyproportional
Ex)
if mA is doubled from 200 to 400, amount of density is also doubled
A minimal change in mA of ________ is needed to visually see a change in density
30-35%
mA and time does not affect _________
scatter radiation
What happens to patient exposure when mA is doubled?
doubling patient exposure
Time (s)
Factor that controls length of exposure
Milliamperes and time are combined and recognized as a single quantitative factor:
(mAs) milliampere seconds
Maintaining the Same Radiographic Density
kV and mAs relationship
A _______ in kV by 15% may be compensated for ___________ the mAs
- decrease
- doubling
_________ in kV by 15 % may be compensated for by _________ the mAs by half
- increase
- decreasing
Maintaining the Same Radiographic Density
mA and time relationship
mA and time is ____________
inversely proportional
Because mAs is considered as ________, an increase or decrease in one will require a decrease or increase in the other to maintain the same radiographic density.
one value
Reciprocity Law
indicates that blackening (density) of the image will remain constant as long as the total energy (total mAs) exposing the image receptor is constant
____________ are necessary to prevent patient motion during exposure, which is detrimental to image quality
short exposure times
