In the case of internal exposure, the radioactivity of the radioactive substances inside the body attenuates, due to elapsed time and as the substances pass through metabolic and excretion processes. During that time, radiation exposure continues to occur in the body. The internal exposure dose is calculated as the total cumulative dose during a simulated 50-year exposure starting from the point the radioactive substance enters the body. Official internal exposure dose values are publicly published and managed. That means the values include anticipated future exposure levels that have not yet occurred. In contrast, external radiation dose values indicate the dose of radiation from outside the body, which is essentially a short-term and one-time exposure dose.
If the internal and external exposure dose values are the same, it means that the internal exposure dose will have the same effect as the external exposure dose, or actually less at that particular point of comparison, considering the anticipated future exposure dose.