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

This paper compares three ways to reduce the detection limits of in vivo measurements by using passive techniques: the use of shielded rooms, the use of underground laboratories and the adjustment of the detector's dimensions to the examined energy. This study indicates that the efficiency of the detector is not the critical parameter for achieving sensitive measurements in the low-energy range and is secondary to optimisation of the background level. However, reduction of the background has a limited impact on the sensitivity of counting due to 40K in the body. This study also shows that the advantage of using deep underground laboratories could be replaced by detectors with properly designed shape and size and used at ground level in normally shielded rooms to reach the necessary limits of detection for in vivo assessment of low-energy photon emitters.