A detector device for determining a position of reaction of gamma quanta, the device comprising: a detection layer comprising: at least one polymeric or inorganic scintillator (12, 22) for absorbing gamma quanta and for emitting and propagating scintillation photons; and photoelectric converters (14,24) for converting light signals of the scintillation photons into electric signals; and at least one additional layer comprising: strips of material (13, 23) for absorbing the scintillation photons and for emitting and propagating secondary photons; and photoelectric converters (15, 25) for converting the light signals for the scintillation photons into electric signals.