Investigation of the spatial distribution of inhaled particulate matter in the human lung and its implications for in-vivo monitoring for the actinides

The distribution of activity in the lungs following inhalation of Nb-92m labelled 1 micron polystyrene microspheres, has been investigated for eight male caucasian subjects. Measurements of the 934 keV gamma-ray emissions from the subjects' lungs using an array of highly collimated sodium iodide detectors have shown the distribution of activity to be non-uniform and attempts have been made to quantify this non-uniformity. The implications of the findings of this study for efficient detector positioning have been considered. (Author)