hyperpolariserade

Hyperpolarisation, or hyperpolarization in American English, refers to a set of techniques used to increase the nuclear spin polarization of atoms far beyond its thermal equilibrium. The resulting non-equilibrium spin states produce NMR and MRI signals that are orders of magnitude stronger than those from conventional acquisition, enabling sensitive detection and real-time observation of molecular processes that are otherwise difficult to study.

The main approaches include dynamic nuclear polarization (DNP), para-hydrogen induced polarization (PHIP) and its variant SABRE, and spin-exchange optical pumping (SEOP) for noble gases. DNP transfers polarization from electron spins in a radical agent to nearby nuclei at cryogenic temperatures, typically using microwave irradiation, and is frequently followed by a dissolution step to create a hyperpolarized liquid suitable for in vivo imaging. PHIP uses para-hydrogen to transfer spin order to a substrate, either via chemical hydrogenation or reversible binding in SABRE, often at mild temperatures. SEOP polarizes nuclei of noble gases such as helium-3 or xenon-129 by optically pumping an alkali metal vapor, with the polarized gas then inhaled for lung imaging or inhalation-based studies.

Applications span magnetic resonance imaging and spectroscopy, most notably metabolic imaging with hyperpolarized carbon-13–labeled substrates (for example, pyruvate) and pulmonary imaging with hyperpolarized xenon-129. The enhanced signals enable tracking of metabolic fluxes and gas distribution in real time. Limitations include the transient nature of the polarization, requiring rapid data acquisition and specialized equipment, plus challenges related to production, handling, and regulatory aspects. Hyperpolarisation remains an active area of research with ongoing efforts to broaden clinical translation.