How does using a grid affect receptor exposure if mAs is not increased to compensate?

How does using a grid affect receptor exposure if mAs is not increased to compensate?

• A. Grids always reduce receptor exposure
• B. Grids reduce receptor exposure unless mAs is increased to compensate
• C. Grids reduce receptor exposure by only absorbing scatter radiation
• D. Receptor exposure increases as grid ratio increases

Answer: (B)

When a grid is used, it serves to improve image contrast by absorbing scattered photons before they reach the film or detector. But the grid also absorbs some of the primary photons that would have contributed to receptor exposure. That means receptor exposure drops when a grid is in place unless you increase the exposure. To keep receptor exposure the same, you must raise the mAs by a factor equal to the grid conversion factor (the amount of exposure lost to the grid). The bigger the grid ratio, the more primary photons are absorbed and the greater the required compensation. So the statement that grids reduce receptor exposure unless mAs is increased to compensate best captures the relationship. Grids don’t reduce exposure only by absorbing scatter—primary radiation is attenuated too—so simply increasing grid ratio would not increase exposure; it would require more mAs to maintain it.

When a grid is used, it serves to improve image contrast by absorbing scattered photons before they reach the film or detector. But the grid also absorbs some of the primary photons that would have contributed to receptor exposure. That means receptor exposure drops when a grid is in place unless you increase the exposure. To keep receptor exposure the same, you must raise the mAs by a factor equal to the grid conversion factor (the amount of exposure lost to the grid). The bigger the grid ratio, the more primary photons are absorbed and the greater the required compensation. So the statement that grids reduce receptor exposure unless mAs is increased to compensate best captures the relationship. Grids don’t reduce exposure only by absorbing scatter—primary radiation is attenuated too—so simply increasing grid ratio would not increase exposure; it would require more mAs to maintain it.