If a radiograph was taken without a grid and then repeated using an 8:1 grid, how many times should the milliampere-seconds (mAs) be adjusted to maintain the same image receptor exposure?

When a radiograph is taken without a grid, the exposure to the image receptor is generally higher due to the lack of a grid, which reduces scatter radiation. When an 8:1 grid is introduced, it absorbs a significant portion of scatter radiation that would otherwise reach the image receptor. As a result, to maintain the same image receptor exposure when using a grid, the milliampere-seconds (mAs) must be increased.

The adjustment factor for an 8:1 grid is typically around 4 times the original mAs used without the grid. This is based on the grid's efficiency in reducing scatter. Therefore, by increasing the mAs by a factor of 4, the radiologic technologist compensates for the reduction in exposure caused by the grid's absorption of scatter.

This understanding allows for maintaining consistent image receptor exposure while ensuring that the final radiograph retains adequate density and detail.