[Hyperpolarized C magnetic resonance imaging-a window into metabolism : High-resolution images of human metabolism].

Clinical Issue: Despite being one of the main pillars of modern diagnostics, magnetic resonance imaging (MRI) uses only a tiny fraction of its potential: no more than a millionth of all nuclear spins contribute to the MRI signal. In order to increase this fraction, called polarization, MRI scanners with stronger magnetic fields are being developed. However, even the most modern scanners do not exploit the potential of MRI.

Methodological Innovations: To make full use of this potential, hyperpolarized MRI (HP-MRI) is an excellent tool: quantum mechanical tricks can be used to generate contrast agents whose nuclear spins can deliver a MRI signal that is up to a 100,000 times stronger. This signal enhancement allows imaging of in vivo processes that would be otherwise impossible to measure. It is particularly interesting to introduce these magnetically labeled nuclei into metabolic processes so that the metabolism can be investigated non-invasively and in vivo.

Performance: Small but diagnostically important changes in metabolism could be found before macroscopic tissue changes were otherwise visible. High-resolution images can be acquired within a few 100 ms, enabling metabolic monitoring in real-time. Heart, brain, and prostate are among the organs that have already been investigated in over 90 clinical trials using this emerging technology.

Achievements: So far, displaying tissue in a similar manner was only possible using nuclear medicine, e.g., positron emission tomography (PET) utilizing radionuclides and without resolution of various metabolic steps. A change in tumor metabolism following treatment was shown within hours in HP-MRI. These applications coupled with background information about the technology are the subject of this review.