A method of magnetic resonance investigation of a sample by (i) reacting ortho-deuterium enriched hydrogen with a hydrogenatable MR imaging agent precursor to produce a hydrogenated (i.e. deuterated) MR imaging agent; (ii) optionally, subjecting the hydrogenated MR imaging agent to a low magnetic field;(iii) administering the hydrogenated MR imaging agent to the sample; (iv) exposing the sample to radiation of a frequency selected to excite nuclear spin transitions of selected non-zero nuclear spin nuclei in said hydrogenated MR imaging agent; (v) detecting magnetic resonance signals of the selected non-zero nuclear spin nuclei from the sample; and (vi) optionally, generating an image or biological functional data or dynamic flow data from the detected signals.