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| What is Filtration? | The process of eliminating undesirable low-energy x-ray photons by the insertion of absorbing materials into the primary beam
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| Filtration is also called __________ because it removes the low energy photons. | Hardening the beam
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| 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.
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| At what keV does significant soft-tissue penetration occur? | between 30 and 40
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| Why is low energy photons insufficient energy? | Because they dont have enough energy to exit the patient and make any contribution to the image.
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| What is a filter? | Any material designed to selectively absorb photons from the x-ray beam.
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| What is the standard filtering material and what terms is it expressed in? | Aluminum...Thickness of aluminum equivalency (Al/Eq)
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| ___________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)
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| What are the types of filtration? | Inherent, Added, Compound, Compensation, and Total
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| Filtration that is a result of the composition of the tube and housing because it is a part of these structures. | Inherent Filtration
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| 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.
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| What is the range for total inherent filtration in mm of Al/Eq | 0.5-1.0mm Al/Eq
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| What causes an increase in inherent filtration? | pitted anode and the vaporized metal on the tube.
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| What is added filtration? | Any filtration that occurs outside the tube and housing and before the image receptor.
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| 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.
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| 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
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| 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.
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| Why are compound filters arranged this way? | So that each layer absorbs the characteristic photons created by the previous layer.
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| Give an example of a compound filter and in what area of radiology is it used? | Thoreaus filter. Radiation therapy.
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| 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.
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| Give examples of compensating filters | Wedge filter and trough filter
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| What are some materials used in compensating filters? | aluminum, lead plastic trademarked ClearPb, or plastic
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| What could a wedge filter be used for? | Procedures on the thoracic spine, feet, and lower extremities.
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| What could a trough filter be used for? | to even the density differences between the mediastinum and the lungs on a chest x-ray
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| What is total filtration? | The sum of inherent and added filtration. (This doesnt include any compound or compensating filter that may be added later)
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