Questions and Answers
What does 'No grid =' equal?
What is the value of 5:1?
What is the value of 6:1?
What is the value of 8:1?
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What is the value of 10:1?
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What is the value of 12:1?
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What is the value of 16:1?
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What is the grid ratio equation?
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If you're going from G to NG, what happens to your mAs?
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If you're going from NG to G, what do you do to your mAs?
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If you're going from one grid ratio to a higher grid ratio, what do you do to your mAs?
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If you're going from one grid ratio to a lower grid ratio, what do you do to your mAs?
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What is the equation for calculating new mAs when changing from one grid to another?
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If you're going from no grid to a grid, you __ mAs by the factor # for specific grid.
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If you're going from a grid to no grid, you __ mAs by the factor # for specific grid.
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If you're just changing grids, what equation do you use?
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If the grid frequency has a higher number, there are more strips so it absorbs more scatter.
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What is the contrast improvement factor (k) equation?
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What is the inverse square law definition?
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What is the inverse square law equation?
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What is the direct square law definition?
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What is the direct square law equation?
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What is the equation for new time station?
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What is the equation for new mA station?
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What is the recommended increase in mAs for a wet plaster cast?
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What is the recommended increase in mAs for a dry plaster cast?
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What is the recommended increase in mAs for a fiberglass cast?
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What law applies to SID changes?
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For every 1 inch increase in SID, what should you do?
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For every 2 inches decrease in SID, what should you do?
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At 34-38 inches SID, by what percentage should you decrease original mAs?
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At 30-33 inches SID, by what percentage should you decrease original mAs?
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For every 1 inch increase of OID, what should you do?
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For every 2 inches decrease of OID, what should you do?
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For every 1 cm increase in tissue thickness, what should you do?
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For every 1 cm decrease in tissue thickness, what should you do?
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What is the 15% rule?
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What kVp change is required to make a visual difference on a radiograph?
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Study Notes
Grid Conversion Factors
- No grid is denoted as 1.
- Common grid ratios include:
- 5:1
- 6:1
- 8:1
- 10:1
- 12:1
- 16:1, with increasing ratios requiring adjustments to mAs.
Grid Ratio Equation
- The grid ratio is calculated using the formula: H/D (height/distance).
mAs Adjustment Rules
- Decrease mAs when converting from Grid (G) to No Grid (NG).
- Increase mAs when converting from No Grid (NG) to Grid (G).
- Increase mAs when moving to a higher grid ratio.
- Decrease mAs when moving to a lower grid ratio.
- To calculate new mAs when changing grid types: New grid multiplier/Old grid multiplier x Old mAs = New mAs.
- When moving from no grid to a grid, multiply mAs by the factor corresponding to the specific grid.
- When moving from a grid to no grid, divide mAs by the factor corresponding to the specific grid.
Grid Frequency
- Higher grid frequency indicates more strips, thus absorbing more scatter.
Contrast Improvement Factor
- The equation for contrast improvement factor (k) is: k = contrast with grid/contrast without grid.
Inverse Square Law
- Definition: Intensity of the X-ray beam decreases inversely with the square of the distance from the source.
- Equation: I1/I2 = D2^2/D1^2.
Direct Square Law
- Definition: Used to determine new mAs when the distance changes.
- Equation: mAs1/mAs2 = D1^2/D2^2.
New mAs Equations
- New time station: mAs/mA = t.
- New mA station: mAs/t = mA.
Adjustments for Casting
- Wet plaster cast: Increase mAs by 150%.
- Dry plaster cast: Increase mAs by 100%.
- Fiberglass cast: Increase mAs by 50%.
SID Changes
- Changing SID will use the Direct Square Law.
- For every 1 inch increase in SID, increase mAs by 5%.
- For every 2 inches decrease in SID, decrease mAs by 5%.
- At 34"-38" SID, decrease original mAs by 30%.
- At 30"-33" SID, decrease original mAs by 50%.
OID and Tissue Thickness Adjustments
- For every 1 inch increase of OID, increase mAs by 10%.
- For every 2 inches decrease of OID, decrease mAs by 10%.
- For every 1cm increase in tissue thickness, increase mAs by 20%.
- For every 1cm decrease in tissue thickness, decrease mAs by 10%.
15% Rule
- Increasing kVp by 15% has the same effect as doubling mAs.
- Decreasing kVp by 15% has the same effect as halving mAs.
Minimum kVp Change for Visual Difference
- A 4-5 kVp change is required to achieve a visual difference on a radiograph.
Studying That Suits You
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Description
This quiz features flashcards focused on grid conversion factors and their corresponding equations. Each card provides a specific grid ratio and its numerical value, helping reinforce understanding of key mathematical concepts in this area. Perfect for students needing to master grid ratios for various applications.
