Question

Exposure factors of 110 kVp and 12 mAs are used with an 8:1 grid for a particular exposure. What should be the new mAs if a 12:1 grid is substituted?

15

Answer 1

To calculate the new mAs when a 12:1 grid is substituted, use the formula: mAs(new) = mAs(old) x (grid factor(new) / grid factor(old)). Substituting the values, the new mAs should be approximately 11.2 mAs.

Step-by-step explanation:

To calculate the new mAs when a 12:1 grid is substituted, we can use the formula:

mAs(new) = mAs(old) × (grid factor(new) / grid factor(old))

First, let's calculate the grid factors:

Grid factor(old) = (1 / grid ratio(old)) + 1 = (1 / 8) + 1 = 1.125

Grid factor(new) = (1 / grid ratio(new)) + 1 = (1 / 12) + 1 = 1.083

Now, we can substitute the values into the formula:

mAs(new) = 12 mAs × (1.083 / 1.125) ≈ 11.2 mAs

Therefore, the new mAs should be approximately 11.2 mAs.