If a radiograph is acquired using 200 mA and 200 ms, what new exposure time must be used with 300 mA for the same receptor exposure?

To solve for the new exposure time when changing the milliampere (mA) from 200 mA to 300 mA while keeping the receptor exposure constant, one must understand the relationship between current (mA) and exposure time (ms) in radiography.

Exposure is directly proportional to the product of mA and exposure time (in seconds). This can be represented as:

Exposure = mA × time

For the initial scenario, with 200 mA and 200 ms, the exposure can be calculated as:

200 mA × 200 ms = 40,000 mAs (milliampere-seconds)

Now, to find the new exposure time when the mA is increased to 300 mA, we want the receptor exposure to remain the same, so:

40,000 mAs = 300 mA × new time

To find the new time, rearranging the equation gives:

new time = 40,000 mAs / 300 mA = 133.33 ms

Rounding this to a practical value results in approximately 133 ms. Thus, for the same receptor exposure, using 300 mA requires a reduction in exposure time to 133 ms. This is consistent with