X-ray emission Flashcards
The number of X-rays in the beam
quantity
the penetrability of the beam
quality
The primary beam is characterized by
Quantity and quality
quantity aka
Intensity and radiation exposure
Factors that affect quantity
mAs
X-ray quantity is ________ proportional to mAs
directly
Double the mAs =
double the intensity
Quantity is _______ to square of the ratio of the Kvp
proportional
distance: quantity varies _______as the quare of the distance from the target
inversely
Quantity is reduced by removing low-energy x-rays
filtration
The low-energy x-rays contribute
_______ useful to the image. They only ______ pt. dose unnecessarily
nothing; increase
Quality AKA
energy; penetrating ability
Distance and mAs
_____ affect quality
do not
Factors that affect x-ray beam quality also influence __________.
radiographic contrast
The quality of x-rays is measured by the _____.
half-value layer
the thickness of absorbing material necessary to reduce the x-ray intensity to 1/2 of its original value
HVL of an x-ray beam
A diagnostic x-ray beam usually has HVL in the range of _____mmAl or ____ of soft tissue
3-5mm Al; 3-6cm
HVL is normally determined _________
experimentally
Quality is increased as KVP is ____________
increased
Quality is increased with _____ filtration
increasing
primary purpose of filtration is to ______________
remove low energy x-rays
Aluminum is primarily used due to:
efficiency- photoelectric effect, avalibility and cost
Inherent filtation
glass or metal enclosure
Since x-ray tube window is very thin, this provides for __________
low inherent filtration
Tube starts out with _____mm Al equivalent and it increases with age due to_____
~.5; sunburning effect
added filtration
a thin sheet of Al between the tube housing nad the collimator
Added filtration shifts the emission spectrum to the _______________
high energy side
Added filtration attenuates x-rays of all energies, but lower energy rays are _______
attenuated more
used to produce a uniform intensity on the image receptor when imaging body parts that vary greatly in thickness
compensating filters
Wedge filter
the most common
Found by adding the thicknesses of the various filters in the tube, collimator housing, and compensating filters
total filtratration
The total number of xrays emitted is _________ to the area under the cure of the xray emission spectrum
equivalent
The general shape of the emission spectrum is always the _______. but the position along the _________ can change
same; energy axis
Factors that can change the shape of the curve are
Ma/mAs, KVP, added filtration
mA/mAs: the ________ the quantity of these, the __________will be all point on the curve.
Greater (less); higher (lower)
KVP: The higher the quantity, the area under the curve______. this will _______ both the quantity of xrays produced and the quality
Increases, increase
added filtration: This will ____ beam intensity while ________ average energy
reduce; increasing
Filtration more effectively absorbs low-energy xrays than high energy xrays: THe breams spectrum is ______ more on the left than the right
reduced
Target material
increasing target atomic number (Z) enhances the efficiency of x-ray production and the energy of characteristic and bremsstrahlung x-rays
Voltage waveform
Quantity and quality of the beam will both be affected by the type of voltage waveform used
