A rem reflects the radiation dose received by the body, after accounting for the potential for harm from different types of radiation. To convert rads to rems, the number of rads is multiplied by a number that reflects the potential for damage caused by a type of radiation. For beta, gamma and X-ray radiation, this number is generally one. For some neutrons, protons, or alpha particles, the number is twenty. A millirem (mrem) is one-thousandth (1/1,000) of a rem.