Radiopharmaceuticals labelled with technetium

The ready availability and ideal nuclear properties of sup(99m)Tc has led to its widespread use for imaging . purposes. In general the localization of the present radiopharmaceuticals is based on the ability of an organ to remove foreign substances from the blood. Further application of this ideal nuclide seems related to the development of methods to label biologically active molecules or drugs in such a way as not to interfere with their desired in vivo behaviour. However, directly binding the sup(99m)Tc to those molecules may prevent the expected distribution (except in the case of large molecular weight proteins and cells) by altering the critical functional groups. Therefore the synthesis of derivatives containing a chelating group to bind the technetium is suggested as a possible solution to the problems associated with direct labelling. This could result in a molecule with similar biological properties to the parent molecule. But before useful derivatives of biologically active molecules and drugs can be prepared, extensive study of the chemistry of sup(99m)Tc is needed. (author)