FIG. 4.
Time skew in dSiPM-1, relative to Die1, can be computed from the mean of the timing spectra acquired with reference to a second detector (Ref. crystal on dSiPM-2) using (tDiex − tDie1 − tstep), where tstep = flight time of an annihilation photon between dies. Note, however, that in a given die, all 4 pixels are aligned in time.