Problems in Defining the Minimum Detectable Activity in Lung Measurement of Low Energy Photon Emitters

Abstract

An intercalibration campaign has been carried out in Italy aimed at evaluating and comparing the performances of NaI(Tl), phoswich and HPGe based detector systems for measurement of transuranic elements (241Am and 239Pu) in lungs. For the calibration, a Livermore realistic chest phantom was used. On the basis of a proposed procedure for MDA evaluation, repeated time delayed measurements of definitely uncontaminated subjects, having different body masses, were performed for 'blank' count evaluation in order to assess both intra-subject and inter-subject count variability. Results of this intercalibration campaign are presented together with MDA values for all NaI(Tl), phoswich and HPGe detector based systems involved. The necessity of a common procedure to assess system performance in in vivo measurement of transuranic elements is discussed and the proposed methodology for evaluation of minimum detectable activity is also presented.