This project is devoted to the development, testing and first applications of a high-resolution single photon imaging technique (Gamma MRI), which combines the detection of gamma ray emission of long-lived nuclear states with Magnetic Resonance Imaging (MRI). This potentially paves the way for a new modality in medical diagnosis, as this technique is much more sensitive than conventional MRI. It benefits from the hyperpolarisation of nuclear spins and from the efficient detection of resonances via the asymmetry of gamma decay. The first tests of the setup with radioactive xenon isomers were carried out during 2018.