Grid Study sheet
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
Help!
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| Define grid. | Device used to improve contrast of the radiographic image.
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| When is a grid used? | Body thickness exceeds 10 cm or kVp is above 60
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| When did Gustav Bucky invent the grid? | 1913
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| When did Hollis Potter invent the moving grid? | 1920
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| Radiolucent interspace materials are usually made out of what 2 materials? | Aluminum and plastic fibers
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| What is the formula for grid ratio? | Grid ratio = h/d
(h = height of lead strips, d = interspace width)
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| Define grid frequency. | Number of grid lines per inch or centimeter.
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| As the lead content of a grid increases, the ability of the grid to remove scatter and improve ____ ______. | contrast, increases
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| Name the 3 grid patterns. | Linear, Criss-cross, Rhombic (LCR)
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| Name the 2 grid types. | Parallel (Lead and interspace materials running parallel), and focused (central grid strips parallel and other strips are inclined.)
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| What is the formula for grid selectivity? | Selectivity = % primary radiation transmitted DIVIDED by
% scatter radiation transmitted
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| What symbol identifies selectivity? | Greek letter Sigma
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| What is the formula for Contrast Improvement Factor K? | K = Radiographic contrast with the grid DIVIDED by
Radiographic contrast without the grid
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| Define off-level. | The tube is angled across the long axis of the strips.
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| Define off-center. | The tube must be centered along the central axis of a focus grid.
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| Define off-focus. | The proper SID is not used.
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| Define upside down. | Occurs if proper distance is not used with the specified distance.
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| What are the 2 types of grid movement? | Reciprocating (back & forth); Oscillating (circular movement)
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| Define air-gap technique. | An alternative to the use of a grid.
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| When is the air-gap technique used? | Magnification radiography
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| What is the disadvantage to using the air-gap technique? | The loss of sharpness that results from increased OID.
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| What is the Moire effect? | Grid error that occurs with digital image receptor systems when grid lines are captured and scanned parallel to the scan lines in the imaging plate readers.
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| An __________ relationship exists between the distance between lead strips and grid ratio when the height of the grid strips remains the same. | Inverse
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| As the lead content of a grid increases, the ability of the grid to remove scatter and improve contrast ____________. | Increases
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| __________ grids are more commonly used in clinical practice because they can be used when performing procedures requiring tube angulation. | Linear
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| The distance from the face of the grid to the points of convergence of the lead strips is called the ___________ __________. | Grid radius
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| For the grid to be properly focus, the x-ray tube must be located along the _________ __________. | Convergence line
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| ______ _______ _________ girds are made for use in mammography. | Short focal range
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| ________ _________ ________ are used for chest radiography. | Long focal range
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| Focused grids with ________ _____ ____ allow for greater latitude in alignment of the tube with the grid. | Lower grid ratios
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| Grid conversion factors __________ with higher grid ratios and increasing kVp. | Increase
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| The grid with the higher lead content would have a ___________ selectivity. | Greater
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