The invention relates to a hybrid medical PET-SPECT/MR imaging device comprising at least one scintillating crystal and at least one module for detecting radiation which contains at least one matrix of photodetectors and an electronics section, such that said module has a mechanical structure, the external, internal or both surfaces of which are divided into at least two sections, of which at least one is coated in graphene, and the rest in non-ferromagnetic conductive material, or all the sections are coated in graphene, and such that the coating forms a Faraday cage. The invention also relates to a shielding against radiofrequency for a medical imaging device, comprising a graphene coating, which is continuous or in bands, on all the faces of the mechanical structure of the detection module of the device, or a graphene coating, continuous or in bands, on at least one face, combined with a coating of non-ferromagnetic conductive materials on the remaining faces, and said shielding forming a Faraday cage.