The present invention relates to a hydrophobic polymer used in particular to produce and/or coat medical devices, in particular implantable medical devices, that are visible in magnetic resonance imaging, characterized in that it comprises at least one monomer unit on which is grafted a chelating ligand of a paramagnetic ion complexed with such a paramagnetic ion, said monomer unit having at least one carbonyl group, said monomer unit comprising, prior to grafting, at least one hydrogen atom in the α position of said at least one carbonyl group, and said grafting of the chelating ligand taking place in the area of said at least one hydrogen atom in the α position of said at least one carbonyl group.