System of imaging by gamma radiation detection comprising at least one processing unit, at least one chassis, and at least one set of detection modules (CP, P) mounted on said at least one chassis and providing at least one signal analysed by said at least one processing unit, each of the modules comprising at least one scintillator that emits photons, when it is subject to the influence of said gamma radiation, at least one photodetector that generates said signal in response to said photons emitted by said scintillator and at least one acquisition device which collects said signal in order to transmit it to said processing unit, the system being characterised in that: - said chassis comprises a plurality of locations distributed over at least one portion of two spherical caps opposite each other defining an imaging volume within the system, said caps being separated by a distance that makes it possible to accommodate an object to be imaged in said volume; - said chassis being open, on at least one side between the two caps, so as to allow free access to said object to be imaged in said volume; - said set of detection modules (CP, P) comprises at least one module of the Compton camera type, having a field of view directed between the two caps, of which the scintillator comprises at least one so-called fast scintillator crystal plate, of which the rise time to peak light is less than 1 ns, so that this module is capable of producing an image using Compton scattering; - said set of detection modules (CP, P) comprises at least one pair of PET modules for detecting coincidences, diametrically opposed to each other on said chassis, each on one of the two caps, defining an imaging axis; - said processing unit analyses the signal from said Compton-type module to determine the intersection of said imaging axis with said field of view and determine the orientations and/or optimum locations of the various detection modules (CP, P) within said caps of the chassis so that the imaging axis passes through the source of said gamma radiation in said object to be imaged. - said chassis comprises a plurality of locations distributed over at least one portion of two spherical caps opposite each other defining an imaging volume within the system, said caps being separated by a distance that makes it possible to accommodate an object to be imaged in said volume; - said chassis being open, on at least one side between the two caps, so as to allow free access to said object to be imaged in said volume; - said set of detection modules (CP, P) comprises at least one module of the Compton camera type, having a field of view directed between the two caps, of which the scintillator comprises at least one so-called fast scintillator crystal plate, of which the rise time to peak light is less than 1 ns, so that this module is capable of producing an image using Compton scattering; - said set of detection modules (CP, P) comprises at least one pair of PET modules for detecting coincidences, diametrically opposed to each other on said chassis, each on one of the two caps, defining an imaging axis; - said processing unit analyses the signal from said Compton-type module to determine the intersection of said imaging axis with said field of view and determine the orientations and/or optimum locations of the various detection modules (CP, P) within said caps of the chassis so that the imaging axis passes through the source of said gamma radiation in said object to be imaged.