Principles of Radiographic Imaging 5th Edition Chapter 18
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| Two Linear grids placed on top of one another so that the lead strips form a criss-cross pattern | Criss-Cross Grid
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| Two linear grids placed on top of one another so that the lead strips form a criss-cross pattern | Cross-Hatched Grid
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| A grid created with the central grid strips parallel with the strips and becoming more inclined as they move away from the central axis; the lines would intersect along a point in space called the line of convergence | Focused Grid
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| A device used to improve contrast of the radiographic image | Grid
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| The result of the primary beam being angled into the lead strips | Grid Cutoff
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| The number of grid lines per inch or centimeter | Grid Frequency
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| The ratio of the height of the lead strips to the distance between the strips | Grid Ratio
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| A grid with lead strips running in only one direction | Linear Grid
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| A grid created with the lead and interspace strips running parallel to one another; the lines will never intersect | Parellel Grid
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| Why does a grid improve contrast? | Grids absorb scattered radiation before it can reach the image receptor
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| As a general rule, when should a grid be used? | Body part thickness exceeds 10 cm, and kVp is above 60
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| How is a grid constructed? | Selection of materials, grid ratio, and grid frequency
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| Define Grid Ratio: | The ratio of the height of the lead strips to the distance between the strips
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| What type of grid pattern has lead strips running in only one direction? | Linear Grid
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| How is a focused grid designed? | The central grid strips are parallel and as the strips move away from the central axis they become more and more inclinded
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| As the ability of a grid to clean up scatter increases, what is the effect on patient dose and image receptor exposure? | The more efficient a grid is at absorbing scatter, the less image receptor exposure. To compensate for the loss of exposure there is an increase in mAs, which increases patient dose.
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| How is the contrast improvement of a grid measured? | The contrast improvement factor. K=radiographic contrast with the grid, over radiographi. The higher the K factor, the greater the contrast.
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| How does an off-level grid error occur? | When the tube is angled across the long axis of the grid strips
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| How does the air-gap technique improve contrast? | The technique involves placing the patient at a greater object IR eistance, that creating an air grap between the patient and IR
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