Grid Conversion Factors & Equations Flashcards
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Questions and Answers

What does 'No grid =' equal?

  • 0
  • 1 (correct)
  • 3
  • 2

    • What is the value of 5:1?

  • 5
  • 2 (correct)
  • 3
  • 1

    • What is the value of 6:1?

  • 3 (correct)
  • 5
  • 2
  • 4

    • What is the value of 8:1?

    <p>4</p> Signup and view all the answers

    What is the value of 10:1?

    <p>5</p> Signup and view all the answers

    What is the value of 12:1?

    <p>5</p> Signup and view all the answers

    What is the value of 16:1?

    <p>6</p> Signup and view all the answers

    What is the grid ratio equation?

    <p>H/D</p> Signup and view all the answers

    If you're going from G to NG, what happens to your mAs?

    <p>Decrease</p> Signup and view all the answers

    If you're going from NG to G, what do you do to your mAs?

    <p>Increase</p> Signup and view all the answers

    If you're going from one grid ratio to a higher grid ratio, what do you do to your mAs?

    <p>Increase</p> Signup and view all the answers

    If you're going from one grid ratio to a lower grid ratio, what do you do to your mAs?

    <p>Decrease</p> Signup and view all the answers

    What is the equation for calculating new mAs when changing from one grid to another?

    <p>New grid multiplier/old grid multiplier x old mAs = new mAs</p> Signup and view all the answers

    If you're going from no grid to a grid, you __ mAs by the factor # for specific grid.

    <p>Multiply</p> Signup and view all the answers

    If you're going from a grid to no grid, you __ mAs by the factor # for specific grid.

    <p>Divide</p> Signup and view all the answers

    If you're just changing grids, what equation do you use?

    <p>NG multiplier/OG multiplier x old mAs = new mAs</p> Signup and view all the answers

    If the grid frequency has a higher number, there are more strips so it absorbs more scatter.

    <p>True</p> Signup and view all the answers

    What is the contrast improvement factor (k) equation?

    <p>k = contrast with grid/contrast without grid</p> Signup and view all the answers

    What is the inverse square law definition?

    <p>The intensity of the X-ray beam is inversely proportional to the square of the distance from the source.</p> Signup and view all the answers

    What is the inverse square law equation?

    <p>I1/I2 = D2^2/D1^2</p> Signup and view all the answers

    What is the direct square law definition?

    <p>Used to determine a new mAs when distance is changed</p> Signup and view all the answers

    What is the direct square law equation?

    <p>mAs1/mAs2 = D1^2/D2^2</p> Signup and view all the answers

    What is the equation for new time station?

    <p>mAs/mA = t</p> Signup and view all the answers

    What is the equation for new mA station?

    <p>mAs/t = mAs</p> Signup and view all the answers

    What is the recommended increase in mAs for a wet plaster cast?

    <p>150%</p> Signup and view all the answers

    What is the recommended increase in mAs for a dry plaster cast?

    <p>100%</p> Signup and view all the answers

    What is the recommended increase in mAs for a fiberglass cast?

    <p>50%</p> Signup and view all the answers

    What law applies to SID changes?

    <p>Direct square law</p> Signup and view all the answers

    For every 1 inch increase in SID, what should you do?

    <p>Increase mAs by 5%</p> Signup and view all the answers

    For every 2 inches decrease in SID, what should you do?

    <p>Decrease mAs by 5%</p> Signup and view all the answers

    At 34-38 inches SID, by what percentage should you decrease original mAs?

    <p>30%</p> Signup and view all the answers

    At 30-33 inches SID, by what percentage should you decrease original mAs?

    <p>50%</p> Signup and view all the answers

    For every 1 inch increase of OID, what should you do?

    <p>Increase mAs by 10%</p> Signup and view all the answers

    For every 2 inches decrease of OID, what should you do?

    <p>Decrease mAs by 10%</p> Signup and view all the answers

    For every 1 cm increase in tissue thickness, what should you do?

    <p>Increase mAs by 20%</p> Signup and view all the answers

    For every 1 cm decrease in tissue thickness, what should you do?

    <p>Decrease mAs by 10%</p> Signup and view all the answers

    What is the 15% rule?

    <p>Increasing kVp by 15% has the same effect as doubling mAs, or decreasing the kVp by 15% will have the same effect as halving the mAs.</p> Signup and view all the answers

    What kVp change is required to make a visual difference on a radiograph?

    <p>4-5</p> Signup and view all the answers

    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.

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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.

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