RADD 2501 Radiographic Grids - Flash Cards

RADD 2501 Radiographic Grids - Flash Cards - minimize grid...

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Grids Reduce scatter radiation, used when part thickness is 10cm (4") or greater, and high kVp is needed Principle function improve image contrast Grid Frequency expresses the number of lead lines per unit length (inches and cm) Grid Frequency Range 25 - 45 line/cm 60 - 110 lines/inch Most common Grid Range 103 lines/inch
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High Frequency requires high radiographic technique, and results in higher pt. dose Grid Ratio height of lead strips divided by the distance between them GR=h/D Grid Ratio Range 4:1 - 16:1 Portable Exams 4:1 GCF mAs2=mAs1xGCF2/GCF1
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High Ratio increase pt. dose, and has lesser latitude Low Ratio wider latitude High Ratio Grids high contrast improvements High frequency grids low contrast improvements Linear (parallel strips) grid lead strips run in one direction, most common grid cutoff
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Criss-Cross or Cross Hatched Grid lead strip run at right angles, remove more scatter, x-ray tube cannot be angled Non-focused grid strips run parallel, fluorscopy, unlimited SID Focused grid lead strips match beam, allow more photons,
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Unformatted text preview: minimize grid cutoff Grid radius height of converge Grid convergence line length of where the meet Specific convergence line 36"-44" or 48"-72" Grid cutoff decrease # of photons reaching the film b/c of misalignment of grid resulting in decrease of density Upside down grid cutoff dark strip down center and grid cutoff on either side of central ray Off center align x-ray tube across the grid or angling the grid producing an overall decrease in density on radiograph Off focus Using SID outside of the focal range creating a loss of density at periphery Reciprocating grids Most common type of grid, moves back and forth laterally High speed bucky reciprocates fast enough to remove grid lines w/ exposure time as fast as 0.0083 (1/20) seconds Oscillating grids moves in circular motion Air Gap used for the same purpose as grids and requires OID increase 5" OID 8:1 grid 10" OID 15:1 Compensate for every cm of OID, mAs increase by 10%...
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RADD 2501 Radiographic Grids - Flash Cards - minimize grid...

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