A summation circuit (1) for summing one or more signals received from a photomultiplier array is proposed. The summation circuit comprises one or more readout circuits (5) coupleable to one or more photodiodes of the photomultiplier array (2), respectively, and a channel summing module (50), coupled at one or more outputs of the one or more readout circuits, respectively, to sum the one or more signals provided by the one or more readout circuits. The one or more readout circuits are coupleable to the photodiode of the photomultiplier array. Each readout circuit (5) comprises one or more coefficient controllers (C1, C2) for controlling multiplying coefficients of the received signal. The coefficient controllers may be placed at the input and/or at the output of the readout circuits (5).