A method of hyperpolarising a magnetic resonance (MR) agent is suitable for use in magnetic resonance imaging (MRI) or magnetic resonance spectroscopy (MRS). The method includes providing a solution comprising the MR agent suitable for use in MRI or MRS and at least one relaxation agent, the relaxation agent being a paramagnetic metal ion having an electron spin relaxation time of less than 1×10−10 seconds at 20° C. The method further includes exposing the solution to a temperature of less than 5 K and a magnetic field of at least 1 T. The relaxation agent may, for example, be dysprosium.
