LOCAL-DISTRIBUTION OF PU-239 USING DIGITISED IMAGES OF NEUTRON-INDUCED AUTORADIOGRAPHS

A procedure has been developed to determine quantitatively the local distribution of Pu-239 in bone from neutron induced autoradiographs (NIARs). A number of frames, sufficient to provide statistically valid data, are randomly selected from the NIAR and photographed through a microscope. These photographs are projected onto a programmed digitising tablet that is connected to a desktop computer. The image of the bone features and the fission tracks are traced manually and converted into their digitised representations. Tracks are assigned separately to bone volume, bone marrow and bone surfaces. Special track patterns such as lines of tracks representing Pu in buried initial surface deposits, diffuse tracks in 'packets' of new bone with a visible track distribution, and clusters of Pu in marrow (stars) are traced as well. All numerical and pictorial information is accessible for further computer processing. An improved procedure to convert fission track densities to local Pu concentrations and to correct for fission tracks originating from slanted bone surfaces is presented. This method provides a reliable and statistically valid basis for the evaulation of all essential parameters necessary for local dosimetry.