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What is Filtration?
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Filtration is also called __________ because it removes the low energy photons.
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Chapter 10
Review
| Question | Answer |
|---|---|
| What is Filtration? | The process of eliminating undesirable low-energy x-ray photons by the insertion of absorbing materials into the primary beam |
| Filtration is also called __________ because it removes the low energy photons. | Hardening the beam |
| What is the primary reason for filtration? | Elimination of photons that would cause increased radiation dose to the patient but would not enhance the radiographic image. |
| At what keV does significant soft-tissue penetration occur? | between 30 and 40 |
| Why is low energy photons insufficient energy? | Because they dont have enough energy to exit the patient and make any contribution to the image. |
| What is a filter? | Any material designed to selectively absorb photons from the x-ray beam. |
| What is the standard filtering material and what terms is it expressed in? | Aluminum...Thickness of aluminum equivalency (Al/Eq) |
| ___________is that amount of absorbing material that will reduce the intensity of the primary beam to one-half its original value and its an indirect measure of the total filtration in the path of the x-ray beam. | Half-value layer (HVL) |
| What are the types of filtration? | Inherent, Added, Compound, Compensation, and Total |
| Filtration that is a result of the composition of the tube and housing because it is a part of these structures. | Inherent Filtration |
| What structures of the tube and housing contributes to inherent filtration? | thickness of the glass envelope of the tube, the dielectric oil that surrounds the tube, and the glass window of the housing. |
| What is the range for total inherent filtration in mm of Al/Eq | 0.5-1.0mm Al/Eq |
| What causes an increase in inherent filtration? | pitted anode and the vaporized metal on the tube. |
| What is added filtration? | Any filtration that occurs outside the tube and housing and before the image receptor. |
| What is the collimators average filtration and where does it come from? | 1.0 mm Al/Eq. Comes from the silver on the mirror situated in the beam. |
| What is a compound filter? What is another name for this? | Two or more materials to complement one another in their absorbing abilites. K-edge filter |
| What materials are used in compound filtering and how are they arranged? | Tin, copper, and aluminum. In that order with highest atomic number closest to the tube and lowest atomic number closer to the pt. |
| Why are compound filters arranged this way? | So that each layer absorbs the characteristic photons created by the previous layer. |
| Give an example of a compound filter and in what area of radiology is it used? | Thoreaus filter. Radiation therapy. |
| What is the purpose of compensating filters? | to add an absorber to compensated for unequal absorption with the subject, thus making the over all absorption of the primary beam more equal. |
| Give examples of compensating filters | Wedge filter and trough filter |
| What are some materials used in compensating filters? | aluminum, lead plastic trademarked ClearPb, or plastic |
| What could a wedge filter be used for? | Procedures on the thoracic spine, feet, and lower extremities. |
| What could a trough filter be used for? | to even the density differences between the mediastinum and the lungs on a chest x-ray |
| What is total filtration? | The sum of inherent and added filtration. (This doesnt include any compound or compensating filter that may be added later) |
Created by:
MissPiggy