"INPUT" AND "OUTPUT" DATA
When evaluating individual radioisotopes to determine their ability to deliver radiation dose to the tissue, it is necessary to consider the decay scheme and both "input" and "output" data. The input data are those which may be determined directly from the decay scheme and the accompanying chart; output data include all possible contributions to the radiation dose. This includes, in addition to the primary radiations listed in the decay scheme, characteristic X-rays, internal conversion electrons, and Auger electrons. The decay scheme for Tc^99m and the table shown below were extracted from the MIRD Booklet (Medical Internal Radiation Dose Committee, a sub-committee of the Society of Nuclear Medicine).

The output data for Tc^99m are shown in the diagram below. While there are 20 contributors to the internal dose from Tc^99m, it should be noted that the majority of them confer a very small radiation dose because their % abundances are very small (<3% of all transitions)

The MIRD Committee has developed a hypothetical "reference man", actually a bisexual construct that permits estimation of the factors required to calculate dose to one organ attributable to a source in another organ. A schematic drawing of this "reference man" is shown below.