The invention provides MRI detectable species of formula (I)Dp-Sn-Nm (I)whereinD is a MRI detectable moietyS is a spacerN is a molecule of a nutrient or pseudo-nutrientn is 0 or an integerm is an integer andp is an integer.These compounds are useful for internalizing into tumor cells an amount of the MRI detectable moiety that is distinguishably higher than the amount internalized in normal healthy cells thus allowing the diagnosis of tumors.The internalization of the MRI detectable moiety involves the nutrients or pseudo-nutrients transporting system. Preferred compounds of formula (I) are those wherein D is the chelated complex of a paramagnetic metal ion.
