ABSTRACT
Using the canonical Medical Internal Radiation Dose (MIRD) format, radiation dose depends on the matrix product of S and Ã. In the computation, Ã is the array of integrals of the time-activity curves A(t) for each source organ. Prior to performing the integration, one must first find the activity values for these sources. After more than a half century of development, it is one of the most surprising aspects of nuclear medicine practice that no standard method exists to determine activity within a living animal or patient. Multiple techniques have been implemented to assist in particular circumstances. There is not yet an optimal method to solve the general problem. This quandary may be termed the problem of nuclear medicine. Because of this lack of information, not only are dose estimates difficult to make, but diagnostic reporting by the clinician is also similarly limited.
