The reduction of limits of detection in in vivo counting of low energy photon emitters by optimizing the shape and size of detectors.

Two main problems are encountered during measurement of internal contamination by the direct methods: the large uncertainties of the results and the reduction of the detection limits. Specially for the radionuclides emitting low energy photons, the systematic errors can be large compared to the recommendations established by the International Committee for Radiological Protection (I.C.R.P.). The purpose of this study is to define the different sources of uncertainties influencing the result of an in vivo measurement, to establish if they are worth to be handled to reduce the uncertainties and to describe the ways these reductions can be obtained. The same considerations will be applied to the detection limits of a measurement by the direct method. This study has been performed in association with a survey of European laboratories