Hyperpolarized MRI - An Update and Future Perspectives.

In recent years, hyperpolarized 13C magnetic resonance spectroscopic (MRS) imaging has emerged as a complementary metabolic imaging approach. Hyperpolarization via dissolution dynamic nuclear polarization is a technique that enhances the MR signal of 13C-enriched molecules by a factor of > 104, enabling detection downstream metabolites in a variety of intracellular metabolic pathways. The aim of the present review is to provide the reader with an update on hyperpolarized 13C MRS imaging and to assess the future clinical potential of the technology. Several carbon-based probes have been used in hyperpolarized studies. However, the first and most widely used 13C-probe in clinical studies is [1-13C]pyruvate. In this probe, the enrichment of 13C is performed at the first carbon position as the only modification. Hyperpolarized [1-13C]pyruvate MRS imaging can detect intracellular production of [1-13C]lactate and 13C-bicarbonate non-invasively and in real time without the use of ionizing radiation. Thus, by probing the balance between oxidative and glycolytic metabolism, hyperpolarized [1-13C]pyruvate MRS imaging can image the Warburg effect in malignant tumors and detect the hallmarks of ischemia or viability in the myocardium. An increasing number of clinical studies have demonstrated that clinical hyperpolarized 13C MRS imaging is not only possible, but also it provides metabolic information that was previously inaccessible by non-invasive techniques. Although the technology is still in its infancy and several technical improvements are warranted, it is of paramount importance that nuclear medicine physicians gain knowledge of the possibilities and pitfalls of the technique. Hyperpolarized 13C MRS imaging may become an integrated feature in combined metabolic imaging of the future.