What unit is commonly used to measure dose?

The most commonly used units for measuring dose, particularly in the context of radiation protection and biological effects from exposure to ionizing radiation, are the rem and millirem (mrem). The rem is a traditional unit that quantifies the biological effect of radiation in terms of the dose absorbed in human tissue, taking into account the type of radiation and its effectiveness in causing biological damage. The millirem is simply one-thousandth of a rem and is often used for more practical measurements due to the typically low doses encountered in occupational settings.

While the gray (Gy) is the SI unit of absorbed dose and represents the energy deposited per kilogram of tissue, it does not factor in the biological impact of different types of radiation as the rem does. The rad is another older unit of absorbed dose, analogous to the gray, but it is less commonly used in current practice. The becquerel (Bq) is a unit of radioactivity, which measures the rate of decay of radioactive substances but does not directly relate to the biological dose received from that radiation.

Thus, rem and mrem are the preferred units when discussing effective dose in a radiological context, establishing why this is the correct answer.