COMPTEL achieved its good signal-to-noise ratio by requiring a coincidence between two independent detector triggers and measuring the time of flight between the two photon interactions over a distance of 1.6 m, the separation of D1 and D2, the detector systems designed for the successive scatters (Schönfelder et al. 1993). The time-of-flight measurement allowed one to distinguish gamma rays traveling in different directions but traversing the same path. However, this large separation of the detectors resulted in a small acceptance angle for the once-scattered photon. To improve this solid-angle factor the independent detecting elements must be moved closer to one another. This, in turn, makes a time-of-flight measurement difficult. Several new designs have detecting elements separated by a few cm or less (Kanbach et al. 2003, Zych et al. 2003), a time-of-flight separation of much less than 1 ns. Therefore, one must supplant the time-of-flight measurement with one that is at least as effective in suppressing background.