The physical and chemical nature of technegas

Technegas, the discrete radio-aerosol particle, containing 99mTc has been investigated, and the chemical evolution and physical properties of the particle demonstrated.

A commercial technegas generator was used to produce aerosols according to standard clinical procedures. The aerosols were collected by electrostatic precipitation and examined with transition electron microscopy (TEM), scanning electron microscopy (SEM) and force microscopy. The chemical evolution was examined by x-ray techniques and thermogravimetric analysis.

The active particle was identified as hexagonal platelets of metallic technetium contained within a thin layer of graphitic carbon. This composite structure is discussed in light of the metal particle behaving as a template for the carbon capsule. The average size of the observed hexagonal platelets, 30-60 nm, was only weakly dependent on the concentration of technetium in the crucible.

The mechanism for the formation of the technegas pancreas has been developed and the particles involved characterized. It appears that the use of other metals also leads to the formation of similar materials.