This invention provides a method of magnetic resonance investigation of a sample, preferably of a human or non-human animal body, said method comprising: (i) producing a hyperpolarised solution of a high T 1 agent by dissolving in a physiologically tolerable solvent a hyperpolarised solid sample of said high T 1 agent； (ii) where the hyperpolarisation of the solid sample of said high T 1 agent in step (i) is effected by means of a polarising agent, optionally separating the whole, substantially the whole, or a portion of said polarising agent from said high T 1 agent； (iii) administering said hyperpolarised solution to said sample； (iv) exposing said sample to a second radiation of a frequency selected to excite nuclear spin transitions in selected nuclei eg the MR imaging nuclei of the high T 1 agent； (v) detecting magnetic resonance signals from said sample； and (vi) optionally, generating an image, dynamic flow data, diffusion data, perfusion data, physiological data (eg. pH, pO 2 , pCO 2 , temperature or ionic concentrations) or metabolic data from said detected signals, wherein said high T 1 agent in said hyperpolarised solution has a T 1 value (at a field strength in the range 0.01-5T and a temperature in the range 20-40°C) of at least 5 seconds.
