Term
| _________ is not part of the useful beam |
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Definition
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Term
| Scatter degrades the image by __________ the scale of contrast |
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Definition
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Term
| Scatter places _________ on the image which are unrelated to patient anatomy. |
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Definition
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Term
| ______________ reduces the total amount of tissue irradiated and improves image quality and reduces patient dose |
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Definition
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Term
| As kVp increases, what happens to the # of Compton interations and scatter? |
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Definition
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Term
| An increase in kVp has what affect on patient dose? |
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Definition
decrease dose:
-decreased photoelectric absorption
-increase in kvp is usually accompanied by a reduction in mAs |
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Term
| increasing kVP has what affect on image quality? |
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Definition
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Term
| decreasing kVp has what affect on interactions? |
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Definition
decreased transmission
increased photoelectric absorption (at patient level)
decreased compton scatter |
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Term
| decreasing kVp has what affect on patient dose |
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Definition
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Term
| decreasing kvp has what affect on image quality |
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Definition
| shorter scale of contrast |
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Term
| Volume of irradiated material is controlled by: |
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Definition
| Field size and patient thickness |
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Term
| ______ and ______ body parts produce more scatter |
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Definition
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Term
| control of scatter using beam restricting devices - decrease field size to anatomy of interest |
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Definition
Benefits:
-unnecessary tissue exposure decreases
-scatter decreases
-scale of contrast shortens
-visibility of detail increases |
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Term
| 3 basic types of beam restrictors: |
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Definition
1. aperture diaphragm
2. cone or cylinders
3. collimators |
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Term
beam restricting device w/ very simple design: flat sheet of metal; usually made of lead or lead lined; opening cut in center
-lead lined or lead plate attached to the x-ray tube
-Shape of hole: any size, but square or circular is most common |
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Definition
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Term
Designed for use in fixed applications with a fixed IR and fixed SID:
-dedicated chest or head units
-trauma units
-dental equipment |
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Definition
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Term
| Disadvantage of the Aperture Diaphragm |
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Definition
Penumbra: Due to proximity to tube port; decreases the closer the beam restrictor is to the object being imaged
Increased off-focus radiation: due to distance from focal spot |
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Term
| _________ is the same size all the way down while __________ flares out and allows divergence |
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Definition
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Term
| These are most commonly employed in imaging of the skull, spine, gallbladder, and breast |
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Definition
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Term
| _______ are no better than aperture diaphragms when reducing penumbra |
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Definition
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Term
| _________ do reduce penumbra and off-focus radiation. They also provide better better beam restriction at a greater distance from the focal spot. |
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Definition
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Term
Used for greater detail in small areas
-the reduction in scatter makes images appear sharper |
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Definition
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Term
| the process of eliminating undesirable low energy photons by the insertion of absorbing materials into the primary beam |
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Definition
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Term
| _________ is standard filtering material |
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Definition
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Term
| filtration needed to reduce the beam to one half of its original intensity |
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Definition
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Term
| typical thickness of inherent filtration |
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Definition
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Term
| Inherent materials include: |
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Definition
-glass envelope
-dielectric oil bath
-glass window of the housing |
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Term
| Tube aging increases inherent filtration because: |
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Definition
| Vaporized tungsten coats the tube window |
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Term
| Any filtration outside the tube and housing is known as: |
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Definition
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Term
| The collimator typically provides ____mm Al/Eq, of added filtration due to silver on the collimator mirror |
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Definition
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Term
| Compound filtration made of two or more materials; each layer absorbs the characteristic photons created in the previous layer |
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Definition
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Term
| filter that evens the radiographic density with parts that have uneven tissue thickness or densities |
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Definition
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