Filtration Chapter 11 Flashcards
What is FILTRATION?
Process of eliminating unwanted low energy Xray photons by insertion of absorbing materials into the primary beam
What is the PURPOSE of filtration?
-To protect the patient by removing low energy photons that would of otherwise contribute to patient dose
Do low energy photons contribute to image quality?
No
After filtering an emission spectrum chart what is the after effect?
-Peak energy did not change
-Low energy photons removed
-Decrease in total amount of photons
-Average energy increased
-Made it harder and stronger
What is another definition for flirtation?
A process of increasing the average energy of Xray beam by taking out low energy xrays (hardening)
What is poly-energetic x ray beam?
its beam of many different energies
Why is an xray beam hetergenous?
because not all xrays are the same energies. Thats why they are Poly energetic
Why do we insert filtration into the primary beam?
To protect the patients by removing low energy photons
The number of photons is what?
the intensity or quantity
How can filtration material be expressed as?
Aluminum Equivalent (AL/Eq)
What is the standard filtering material?
Aluminum
What is Half-Value Layer?
the amount of filtration needed to reduce the beam to one half of its original intensity
What is the amount of filtration required by law with a operating range BELOW 51?
0.5mm aluminum
What is the amount of filtration required by law with a operating range of 51 to 70?
1.5mm aluminum
What is the amount of filtration required by law with a operating range ABOVE 70?
2.5mm aluminum
What are the types of filtration? (5)
Inherent
Added
Compound
Compensating
Total
What is inherent filtration?
A filtration that is the result of composition of the tube and housing
What contributes to the inherent filtration?
-thickness of the glass envelope
-dielectric oil
-the glass window of the xray tube housing
What is the typical x-ray tube total inherent filtration?
0.5-1mm AL/Eq
Why does tube aging increase inherent filtration?
because of vaporized tungsten
What is ADDED FILTRATION?
Any filtration outside of the tube and housing
NOTE
(Added filter)
Material are selected to absorb as many low energy photons as possible while transmitting maximum number of high energy photons
NOTE
(Added filter)
-Collimator averages about 1mm AL/Eq that most comes from sliver in the mirror
-1mm AL/Eq is added to exit port
What is TOTAL FILTRATION?
Its the sum of inherent and added filtration