On the “artificial” nature of Tc and the “carrier-free” nature of 99mTc from 99Mo/99mTc generators

Two widespread misconceptions regarding Tc are dealt with. First, it is shown that although primordial Tc has decayed completely, Tc is still present in nature due to natural processes, in addition to substantial man-made quantities. Thus, Tc cannot be considered as a purely artificial element. Second, it is shown that 99mTc from 99Mo/99mTc generators is certainly not carrier-free (CF) and that, “no-carrier-added” (NCA) is a more appropriate designation. As a quantitative measure of the amount of long-lived 99gTc carrier present in 99mTc preparations from generators, the Isotope Dilution Factor (IDF) is used and calculated for some practical situations.