Estimation of 241Am and 239Pu activity embedded in the tissue using portable planar HPGe detector

This paper describes a procedure for the estimation of 241Am and 239Pu activity present in the human tissue by measuring the depth of contaminant using a portable Planar High Purity Germanium detector (HPGe). The ratios of photopeak counts of X-rays or gammas obtained with the detector coupled to collimator are calculated for the estimation of depth of the contaminant and the optimum one is determined. Since Minimum Detectable Activities (MDA) for the detector coupled to a collimator are higher than that of bare detector, activity must be estimated using bare detector, after locating the contaminant. Two methods are described for the estimation of plutonium coexisting with 241Am: (i) Abundance and isotopic correction for 239Pu (ii) and 239Pu:241Am ratio. The procedure to estimate 239Pu when plutonium isotopes alone are present is also established. An optimum monitoring period to detect the minimum value of intake for both radionuclides corresponding to chelation therapy and excision is also derived.