Beam Review
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| what makes up inherent filtration? what is total filtration? | envelope(pyrix glass) and oil(gets rid of heat).
inherent(0.5mm) + added Al Layer(1.0mm)
total equals 2.5mm Al with mirror (1.0mm)
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| what is advantage of filter? | lower patient dose
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| if we don't have enough oil what do we add? | ml of Aluminum
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| if we have filtration, true or false we eliminate a certain quantity of radiation from striking the patient image receptor | true
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| if we have filtration that stops radiation from striking patient image receptor, what happens to density | lower
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| when we harden the beam is equivalent to higher or lower Kvp | higher
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| what happens to contrast when we harden the beam | decreases
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| FDA requirements below 50 kvp | .5
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| FDA requirements 50-70 | 1.5
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| FDA requirements 70-100 Recommend? | 2.5
3.0
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| FDA requirements above 100 | 3.0
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| where is the filter located in the system | between the tube and the patient
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| what is the purpose of a compensating filter | to make up for lost of contrast and densities in certain areas, tissue difference densities.
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| what are two types of compensating filters | wedge- filter with foot or t-spine)
trough- filter with cxr(chest)
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| what is the purpose of beam restriction or collimation | lower patient dose, not letting as much radiation through, lessening the scatter
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| if we properly collimate and compensate with our techniques what does it do to contrast, what are some advantages | improves it. improve contrast, less scatter, reduce patient dose
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| what is the simplest type of filtration. could you vary field size | aperture, 1st kind used. No (disadvantage)
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| what is the filtration with the straight extension, Flared? | cylinder, Cone
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| what is pneumbra | blurring on the edge
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| what is shadowing or ghost beyond the collimating called | stem or off focus
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| if we properly use beam restriction, what do we improve on our image | contrast(improves image quality)
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| for a collimator what degree should the mirror sit, how can we test if mirror is off | 45 degrees, 8 penny test
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| if the mirror sat 15 mm from the focal spot how many mm would it have to sit from the light | 15 mm has to be equal
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| what is the purpose of entrance shutter? movable part? | eliminate off focus radiation.
collimator shutters
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| what does PBL stand for | Positive Beam Limitation device, an automatic collimator or beam restrictor that adjusts to the size of the image receptor for each x-ray.
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| if we collimate from a 14x17 to a 10x12 we? 8x10 | increase 40% Mass, increase 60% Mass
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| the standard for the 8 penny test is | the width of the penny which is 2% of SID, and at 40" SID
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| what is the purpose for filters | to harden the beam and reduce patient skin dose
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| what is HVL | half value layer-amount of absorber required to reduce initial beam intensity by 1/2 or 50%
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| what are the two types of filters | Aluminum and Copper
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| what decreases with collimation and what increases | scatter decreases, and contrast increases
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| why do you have to increase mAs with beam restriction | to prevent density decrease.
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| what are the components of collimator | 1.) Focal spot
2.)Filter( Entrance shutters)
3.)Mirror at 45 degrees
4.)light(lamp)
5.) Second stage shutters(cross shutters)
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