Placement of HPGE detectors for whole body counting applications using simulations of voxel phantoms

The partial body counter at KIT is going to be rebuilt in order to replace the old Ge detectors with four new HPGe detectors. The new installation will also add whole body capabilities to the system, thanks to an improved mechanics able to position the detectors with a high degree of freedom in the chamber. During the definition of the position of the detectors a compromise between the opposite goals of high efficiency and small dependence of the detection efficiency on the position of the source had to be sought. High detection efficiency involves placing the detector near the skin, where the photon flux is maximal, while the second goal involves placing the detectors at a greater distance from the body. The same concept was applied during the definition of the partial body measurement configurations, but the goal was the increase of the specificity of the measurement. In addition, the mechanical installation poses some constraints: two detectors are mounted on carts and therefore can be placed independently around the subjects, but not in front of it, while the other two detectors are mounted on carts hanging from the same rail on the ceiling, therefore their distance from the subject is constrained by the maximum offset between them. (orig.)