Procedure for discrimination between healthy and tumor tissue, said procedure comprises (a) obtaining a 13 C-RM image of 13 C-pyruvate, a 13 C-RM image of its alanine metabolite containing 13 C and an image of 13 C-RM of its lactate metabolite containing 13 C of a subject to which a composition comprising 13 hyperpolarized C-pyruvate was pre-administered, (b) correcting the lactate image by the amount of pyruvate and / or alanine by the multiplication of the Lactate image by the inverted image of pyruvate and / or alanine, a high image signal within said corrected lactate image is indicative of tumor tissue.
