If the entrance dose for a particular exam is 1200 mGy, what is the approximate radiation exposure at 1 m from the patient?

To determine the approximate radiation exposure at 1 meter from the patient when the entrance dose is 1200 mGy, we utilize the concept of the inverse square law, which states that the intensity of radiation decreases with the square of the distance from the source.

In this scenario, the entrance dose of 1200 mGy refers to the radiation dose delivered to the patient at the point of entry. As distance from the source increases, the radiation spread over a larger area results in a lower dose at that distance. When calculating the exposure at a distance of 1 meter from the patient, it is essential to consider a conversion factor that typically accounts for this rapid decrease in intensity due to distance.

In practical clinical terms, for many medical X-ray examinations, the exposure at 1 meter from the patient is often approximately 1/1000th of the entrance dose. Consequently, taking 1200 mGy and dividing it by 1000 results in an approximate radiation exposure of 1.2 mGy at 1 meter.

This aligns with the answer choice of 1.20 mGy, accurately reflecting the expected radiation exposure at that distance from the patient due to the entrance dose provided.