Three-dimensional geometric sensitivity calculation for three-headed coincidence imaging

All major gamma camera manufacturers nowadays offer two-headed coincidence imaging with their gamma camera systems. To improve sensitivity, three-head ed coincidence imaging has been proposed. In an earlier work, we investigat ed how the two-dimensional sensitivity varies in the field of view of such a system. In this paper, these calculations are extended to three dimension s, taking into account the finite axial length of the detector. The extensi on to three dimensions becomes particularly important when one acquires dat a in fully three-dimensional mode, without using axial septa. The three-dim ensional sensitivity calculation presented here is valid for any position o f the camera, such as a U-shaped configuration or a triangular configuratio n. We have also investigated the use of axial septa by constraining the max imum axial incidence angle.