If a radiographic exposure at 40 inches yields 10 milligray (mGy), what is the new exposure when acquired at 72 inches with the same technical factors?

To determine the new exposure at a different distance while using the same technical factors, the inverse square law can be applied. This law states that the intensity of radiation is inversely proportional to the square of the distance from the radiation source.

In this case, the original exposure is measured at 40 inches with a dose of 10 mGy. When the exposure distance is increased to 72 inches, the calculation involves squaring the ratio of the distances:

1. Calculate the ratio of the distances:

• Distance ratio = (72 inches / 40 inches) = 1.8

2. Since the intensity is inversely proportional to the square of the distance, we need to square this ratio:

• Squared distance ratio = (1.8)² = 3.24

3. The new exposure can be calculated using the initial exposure and adjusting for the squared distance ratio:

• New exposure = Original exposure / Squared distance ratio

• New exposure = 10 mGy / 3.24 ≈ 3.09 mGy

This rounds approximately to 3.1 mGy, confirming that the calculation aligns with the expected results. By using the inverse square law correctly, it becomes evident