Final answer:
To compensate for the higher absorption of a 12:1 grid compared to a 6:1 grid in an X-ray tube, the milliampere-seconds value should be increased. By using the grid conversion factors, the new mAs value is calculated to be 10 mAs for the 12:1 grid.
Step-by-step explanation:
The student's question involves changing the grid ratio on an X-ray tube from a 6:1 to a 12:1 grid and determining the new milliampere-seconds value. When changing from a lower ratio grid to a higher ratio grid, more radiation is absorbed by the grid, so the mAs must be increased to maintain the same exposure. The formula to calculate the new mAs when changing grids is: mAs1/mAs2 = GCF1/GCF2, where GCF is the grid conversion factor.
For a 6:1 grid, the GCF is typically 3, and for a 12:1 grid, the GCF is usually 5. Using the initial mAs (6 mAs) with a 6:1 grid, we can find the new mAs needed for a 12:1 grid. (6 mAs / New mAs) = (3 / 5). Solving for New mAs, we find it equals 10 mAs.
In this scenario, the exposure factors are 100 kVp (kilovoltage peak) and 6 mAs (milliampere-seconds) using a 6:1 grid. By substituting a 12:1 grid, the mAs should be increased to 10 mAs to maintain the same level of exposure.