If a change from an 8:1 grid to a 12:1 grid is made, what should the new mAs be if the original exposure used 12 mAs?

When transitioning from an 8:1 grid ratio to a 12:1 grid ratio, it is important to understand how grid ratios affect exposure. The primary purpose of a grid is to reduce the amount of scatter radiation that reaches the film or detector, which in turn improves image quality. However, higher grid ratios require higher exposure due to their increased ability to absorb scatter radiation.

The 8:1 grid has a certain level of efficiency in managing scatter radiation, while the 12:1 grid is more efficient. This means that when moving to a grid with a higher ratio, you need to increase the milliampere-seconds (mAs) to compensate for the increased absorption of scatter.

To determine the new mAs required when changing from an 8:1 grid to a 12:1 grid, you can use a commonly accepted guideline: increasing the mAs by a factor of about 1.5 to 2 times when going from an 8:1 grid to a 12:1 grid.

Starting with 12 mAs for the original exposure, if we apply a multiplier of 1.5, the calculation would be:

Original mAs (12) × 1.5 = 18 m