Final answer:
To convert the required mAs from a 16:1 grid ratio to an 8:1 grid ratio, divide the original 60 mAs by the old grid conversion factor (4) and multiply by the new grid conversion factor (2) to get the new mAs, which is 30 mAs.
Step-by-step explanation:
When changing from a 16:1 grid ratio to an 8:1 grid ratio, the amount of mAs (milliampere-seconds) required will decrease because a lower grid ratio means less radiation is absorbed by the grid, hence less mAs is needed for the same image quality. The exact amount of mAs to be used can be determined using the grid conversion factor (GCF), which for 16:1 is typically around 4 and for 8:1 is typically around 2. Therefore, calculating the new mAs involves dividing the original mAs by the old GCF and multiplying by the new GCF. In this case:
- Original mAs: 60
- Old grid ratio GCF (16:1): 4
- New grid ratio GCF (8:1): 2
The formula for the new mAs would be: New mAs = (Original mAs / Old GCF) × New GCF
Thus:
New mAs = (60 / 4) × 2 = 30
So, if an exposure with a 16:1 grid ratio requires 60 mAs, then an exposure with an 8:1 grid ratio would require 30 mAs.