Loyola University Medical Education Network

Chemical reactivity

One of the features that makes Tc-99m such an ideal radioisotope for diagnostic imaging is its ability to readily bind to a wide variety of compounds under physiological conditions. The literature continues to document Tc-99m's versatility in forming compounds, from simple molecules like pyrophosphate to sugar analogues like glucoheptonate; from peptides to antibodies; from insoluble colloids and macroaggregates to antibiotics and other complex molecules.

In addition, special consideration must be given to the availability of substrates for radiolabeling reactions. Not every compound can be labeled with every isotope and, in fact, labeling is often quite selective. Compounds which demonstrate acceptable biodistribution often become useless when a radiometal is added or the molecule is iodinated. Even minimal changes in the molecular structure are often enough to completely change the biodistribution. Extensive research is required to determine the optimal molecular structure for a particular molecule to be labeled with a specific isotope.


Stephen Karesh, PhD.

Last Updated: August 14, 1996
Created: March 1, 1996