EVIDENCE FOR THE LONG-TERM BIOLOGICAL DISTRIBUTION OF TECHNEGAS PARTICLES

Technegas is a suspension of structured graphite ellipsoids, between 5 and 20 nm in aerodynamic diameter and labelled, in a carrier gas of a rgon, with Tc-99m. Its emergence and rapidly expanding dinical usage ( 105 000 studies, 22 countries), as a unique dry insoluble microaerosol for diagnostic lung imaging, has prompted a review of reports of expe riments on lung clearance with other aerosols. No direct comparison ex ists although it is clear that experimental inhalation insults which d eliver to the alveoli a mass of material orders of magnitude greater t han Technegas are well tolerated by human volunteers.