Symbol Definition The Medical Internal Radiation Dose (MIRD) Committee of the Society of Nuclear Medicine

has developed basic equations for calculating the radiation dose to a patient from a radio pharmaceutical. These equations are analyzed and modified so that the dose to a specific or gan may be calculated when the radionudide is not uniformly distributed in the body. Without the modifications, the dose to a target organ may be overestimated because the amount of radionuclide in the organ is included in the equation twice. The dose to a patient from a radiopharmaceutical is usually calculated with the help of the equations published by the Society's Medical Internal Radia tion Dose (MIRD) Committee (1). When calcu lating the dose to an organ irradiated by activity in that organ and in surrounding organs or the remain der of the body, care must be taken that the activity in the target organ is not used twice in the calcula tion. To avoid this problem, Smith (2) suggested a method which can be described by considering the dose to the spleen when irradiated by activity in the spleen and the total body. i58 =;@ @ + @: + [ATB _ AK