Narrowing coincidence timing window through time-walk correction in silicon ring enhanced PET scanner

We have constructed an enhanced PET scanner from a 1 mm thick silicon detectors as the inner detectors combined with a partial BGO ring. The inner detector trigger is provided by a leading edge discriminator on a CR-RC shaped signal induced by annihilation photon interactions. A shaping time of 150 ns implies a time-walk of similar duration, requiring comparably long hardware coincidence timing windows. The system was set to a planar mode and tested using a Jaszczak phantom with, among others, 1.6 mm diameter holes which match systematic resolution of the mixed mode silicon-BGO events.