<prompt> The SI unit of radiation absorbed dose isRadBecquerelGraySieve  <response>: Ref Robbins 9e p428 Gray is a unit that expresses the energy absorbed by the target tissue per unit mass Radiation UNITS Roentgen: Is the measurement of energy produced by Gamma or X-Ray radiation in a cubic centimeter of air. It is abbreted with the capital R. One milliroentgen, abbreted mR is one-thousandth of a roentgen. One microroentgen, abbreted uR is one-millionth of a roentgen. RAD: Radiation Absorbed Dose. Original measuring unit for expressing the absorption of all types of ionizing radiation alpha, beta, gamma, neutrons, etc into any medium. One rad is equivalent to the absorption of 100 ergs of energy per gram of absorbing tissue. System International SI Units The System International S.I. unit units for radiation measurements are gray Gy and sive Sv for absorbed dose and equivalent dose respectively. The conversion from one system to another is simple: 1 Sv 100 rem 1 rem .01 Sv 1 mSv 100 mR mrem 1 mR .01 mSv 1 Gy 100 rad 1 rad .01 Gy 1mGy 100 mrad 1 mrad .01 mGy 