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Beam Restriction
Beam Review
| Question | Answer |
|---|---|
| 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) |
| what is advantage of filter? | lower patient dose |
| if we don't have enough oil what do we add? | ml of Aluminum |
| if we have filtration, true or false we eliminate a certain quantity of radiation from striking the patient image receptor | true |
| if we have filtration that stops radiation from striking patient image receptor, what happens to density | lower |
| when we harden the beam is equivalent to higher or lower Kvp | higher |
| what happens to contrast when we harden the beam | decreases |
| FDA requirements below 50 kvp | .5 |
| FDA requirements 50-70 | 1.5 |
| FDA requirements 70-100 Recommend? | 2.5 3.0 |
| FDA requirements above 100 | 3.0 |
| where is the filter located in the system | between the tube and the patient |
| what is the purpose of a compensating filter | to make up for lost of contrast and densities in certain areas, tissue difference densities. |
| what are two types of compensating filters | wedge- filter with foot or t-spine) trough- filter with cxr(chest) |
| what is the purpose of beam restriction or collimation | lower patient dose, not letting as much radiation through, lessening the scatter |
| 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 |
| what is the simplest type of filtration. could you vary field size | aperture, 1st kind used. No (disadvantage) |
| what is the filtration with the straight extension, Flared? | cylinder, Cone |
| what is pneumbra | blurring on the edge |
| what is shadowing or ghost beyond the collimating called | stem or off focus |
| if we properly use beam restriction, what do we improve on our image | contrast(improves image quality) |
| for a collimator what degree should the mirror sit, how can we test if mirror is off | 45 degrees, 8 penny test |
| 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 |
| what is the purpose of entrance shutter? movable part? | eliminate off focus radiation. collimator shutters |
| 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. |
| if we collimate from a 14x17 to a 10x12 we? 8x10 | increase 40% Mass, increase 60% Mass |
| the standard for the 8 penny test is | the width of the penny which is 2% of SID, and at 40" SID |
| what is the purpose for filters | to harden the beam and reduce patient skin dose |
| what is HVL | half value layer-amount of absorber required to reduce initial beam intensity by 1/2 or 50% |
| what are the two types of filters | Aluminum and Copper |
| what decreases with collimation and what increases | scatter decreases, and contrast increases |
| why do you have to increase mAs with beam restriction | to prevent density decrease. |
| 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) |
Created by:
johnsoni1986
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