An NMR experiment on hyperpolarizable magnetic nuclei of substrate molecules in a living human or animal body, involves polarizing the substrate molecules by non-hydrogenating para-hydrogen induced polarization (=NH-PHIP) into a singlet/pseudo singlet state in low magnetic field and injecting the substrate molecules into the living body, the body or a part thereof being previously located inside a magnet at low magnetic field. The magnet is switched on to high magnetic field, and in at least part of the substrate molecules, the singlet state/pseudo singlet state is converted into observable magnetization. An MRI or MRS measurement is carried out with the living body or the part thereof, collecting data from the substrate molecules. The NMR experiment is well applicable on hyperpolarized nuclei within a patient, with reduced losses of magnetization due to relaxation processes.