X-ray emission and Image Quality Flashcards
Xray quantity is:
The number of X-rays in the useful beam.
Radiation exposure =
xray intensity = xray quantity.
Radiation exposure, xray intensity and xray quantity are all measured in:
Roentgens (mR)
Roentgen:
a unit of radiation exposure - interaction of X-rays with air.
Factors affecting xray quantity are:
mAs
kVp
Distance
Filtration
The factors that affect X-ray quantity are similar to those affecting:
Optical density
Optical density:
degree of blackness on a film/image.
Optical density is also called:
radiographic density or simply density.
Milliampere (mA)
the unit used to measure the tube current.
Tube current measures:
number of electrons flowing per unit time between cathode and anode.
mA set by radiographer determines:
number of electrons flowing in tube and quantity of X-rays produced.
Higher mA results in:
more electrons that are available in tube current.
The more electrons in tube current:
The more X-rays will be produced.
Quantity of X-rays produced are directly proportional to:
the milliamperage. Therefore, the more mA, the darker the image. Also exposure time.
Longer exposure time results in:
more electrons that move in tube current from cathode to anode.
mA and time are ___________ when maintaining the same mAs.
inversely proportional.
The distance between the source of radiation and the image receptor affects the amount of ______ produced on a radiograph.
density
Xray quantity varies inversely with the
square of the distance from the source.
Inverse square law formula:
I one/I two = D two squared/D one squared.
What is the direct square law used for?
to calculate the new mAs when changing SID in order to maintain the same OD (kVp is constant.)
Direct square law:
When the SID is increased the mAs must be increased by SID squared to maintain constant optical density.
Direct square law formula
I one/ I two = D one squared/D two squared.
When increasing distance, mAs must be ______ to maintain same OD.
increased.
When decreasing distance, mAs must be ______ to maintain same OD.
decreased.