Tc-generators — Yield of ^99mTc and ratio to ‘inactive’ ⁹⁹Tc

Abstract

A large amount of inactive ⁹⁹Tc in some delicate labeling techniques may adversely affect the results obtained. Therefore, it is important to know the ratio (Q(t) of inactive ⁹⁹Tc to active ^99mTc, which is dependent on the time (t) elapsed since the last elution. On the other hand, in optimizing the use of Tc-generators it is desirable to know the actual yield Y(t) at any time (t) after a preceding elution. In this paper, formulas both for Q(t) and for Y(t) are derived and numerical values are tabulated. In combination with a table of the amount of ⁹⁹Mo left, M(t), all the properties of a Tc-generator and of its eluates may be derived and theoretical and practical results compared. This information will help in both optimizing the use of Tc-generators and improving quality control in radiopharmaceutical laboratories.