1. A GAMMA/RF compact, hybrid and integrated system for PET-SPECT/MR simultaneous imaging having a GAMMA/RF device comprising: an RF coil comprising spaces that allow a passage of at least a significant part of a GAMMA radiation generated internally; and a set of GAMMA radiation detector modules arranged radially around the RF coil, wherein each GAMMA radiation detector module comprises: a scintillator crystal configured to emit light when it receives GAMMA emission, a focusing system comprising: a first face, coupled to the scintillator crystal, configured to receive the light, and a second face comprising lenses configured to direct the light onto an array of photodetectors, an RF shielding layer, placed between the focusing system and the array of the photodetectors, comprising holes through which the focused light is directed to the photodetectors, the array of the photodetectors placed behind the RF shielding layer so as to receive the light, and a processor configured to process signals generated by the photodetectors.