  Magnetic Resonance Imaging (MRI) can be considered one of the most effective
techniques in both clinical diagnostic medical field and biomedicine, as it
allows to obtain images anatomy of the body and its various parts and
information functional, such as flow, perfusion, diffusion, motion, etc.. It is
based on the interaction of nuclei with magnetic spin number different from
zero with the magnetic field outside and, in theory, could be used for the
analysis of different nuclei, such as 1H, 13C, 31P (endogenous) or 129 Xe, 3He
(Exogenous). In practice, however, the clinical use of MRI is limited analysis
of 1H that, compared to the others, manifest the highest concentration in the
human body. The use of contrast media usually lengthens the execution time of
an examination of MRI. These, however, would greatly directly reduce by
increasing the intensity of the substrate signal. This can be achieved through
an increase in the substrate polarization via the creation of an equilibrium
state where the population difference between levels is increased. This state
is called hyperpolarized. In recent years have been designed and developed
several techniques for achieving this goal. Hyperpolarized contrast agents
therefore act very differently from classical ones, because, instead of
modifying the signal due the protons surrounding themselves, become themselves
a source of signal. In order to be functional such contrast agents should be
characterized by a high longitudinal relaxation time T1, because the
hyperpolarized state must remain as long as possible after injection into the
circulatory system of the patient.
