Exact rotational weights for coincidence imaging with a continuously rotating dual-headed gamma camera

In Dual Head Coincidence Imaging (DHCI), rotational weights must be applied to detected coincidence events to compensate for varying dwell-times. The dwell-time depends on both the transaxial and axial distance coordinates describing a coincidence line in parallel projection space. An exact formula is derived for the dwell-time of a DHCI camera with continuous detector rotation given a coincidence line described in parallel projection coordinates. The formula is verified by simulation. In addition, the boundary of the region where Ilo data are measured is described. This missing-data region differs from that of a cylindrical PVI system whose diameter is the same as the head separation of the DHCI system and whose axial extent is the same as the axial dimension of the rotating planar detectors in the DHCI system.