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 (B)</p> Signup and view all the answers

What is the value of 10:1?

<p>5 (A)</p> Signup and view all the answers

What is the value of 12:1?

<p>5 (A)</p> Signup and view all the answers

What is the value of 16:1?

<p>6 (A)</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 (A)</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% (A)</p> Signup and view all the answers

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

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

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

<p>50% (D)</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

Flashcards

Grid Ratio

The ratio of the height of the lead strips to the distance between them.

mAs Adjustment from Grid to No Grid

Decrease mAs when converting from Grid (G) to No Grid (NG).

mAs Adjustment from No Grid to Grid

Increase mAs when converting from No Grid (NG) to Grid (G).

Increasing mAs with Higher Grid Ratios

Increase mAs when moving to a higher grid ratio.

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Decreasing mAs with Lower Grid Ratios

Decrease mAs when moving to a lower grid ratio.

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New mAs Calculation

New mAs = (New grid multiplier/Old grid multiplier) x Old mAs.

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Grid Frequency

Higher grid frequency means more lead strips are present.

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Contrast Improvement Factor (k)

k = contrast with grid / contrast without grid.

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Inverse Square Law

Intensity decreases inversely with the square of the distance.

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Direct Square Law

Used for calculating new mAs when distance changes.

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New Time Station Equation

New mAs/mA = time (t).

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Adjustments for Wet Plaster Cast

Increase mAs by 150% for wet plaster casts.

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Adjustments for Dry Plaster Cast

Increase mAs by 100% for dry plaster casts.

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Adjustments for Fiberglass Cast

Increase mAs by 50% for fiberglass casts.

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SID Change Effects

Changes in SID use Direct Square Law for mAs adjustment.

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OID Adjustments

Increase mAs by 10% for every 1 inch of OID.

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Tissue Thickness Adjustments

Increase mAs by 20% for every 1cm increase in tissue thickness.

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15% Rule

Increasing kVp by 15% doubles mAs; decreasing by 15% halves mAs.

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Minimum kVp Change for Visual Difference

A change of 4-5 kVp is needed for a visual difference.

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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.

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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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