The invention concerns a method for improving the energy resolution of a gamma ray detector comprising a monolithic scintillator and a photodetector segmented during a scintillation event characterized by the following steps:—detecting the time of arrival of the first photons on said photodetector;—counting, during a period T, which is between 2 and 6 times a transfer time (Te), the number and location of the first detected non-scattered photons;—determining the diameter and the position of a disk defined by a set of first non-scattered photons;—determining the position (X, Y) of a scintillation event from the location of said first detected non-scattered photons;—counting the number of the first detected non-scattered photons inside said disk during a period Td greater than a decay time (T) of the scintillator;—defining the energy of a gamma photon, said energy being proportional to the number of non-scattered photons counted inside the disc. The invention also concerns the associated detection system, the microelectronic component and a scintillator crystal treated for use in a PET application, and the use of the detection system according to the invention in PET and SPECT imagers.