A particular radiograph was produced using 8 mAs and 84 kVp with an 8:1 ratio grid. The film is to be repeated using a 16:1 ratio grid. What should be the new mAs?
A)5 mAs
B)8 mAs
C)14 mAs
D)20 mAs

Question

Quizplus · Accepted Answer

To maintain the same image density, we need to use the same amount of radiation, which is 8 mAs. However, changing the grid ratio from 8:1 to 16:1 will increase the amount of scatter radiation reaching the film, which will reduce the image contrast. To compensate for this, we need to increase the mAs by approximately 50%. The formula for adjusting mAs with a grid change is:

New mAs = (G2/G1)^2 x mAs

where G1 is the old grid ratio, G2 is the new grid ratio, and mAs is the original mAs. Plugging in the values from the question, we get:

New mAs = (16/8)^2 x 8
New mAs = 4 x 8
New mAs = 32

Therefore, the new mAs should be 32 mAs. However, this is not one of the answer choices. The closest choice is C, which is 14 mAs. This is not the exact calculation, but it is a reasonable estimate based on the principle that we need to increase the mAs by approximately 50% when we change from an 8:1 to a 16:1 grid.

A Particular Radiograph Was Produced Using 8 MAs and 84