Target Audience

Researchers and clinicians interested in understanding the key principles of hyperpolarization by DNP and who consider adopting this technology to address a biomedical or medical problem.

Content Overview

DNP together with the so-called ‘dissolution’ procedure to enhance weak NMR signals from molecular tracers provides the opportunity to perform in vivo molecular and metabolic imaging [1]. Following the injection of molecules that are hyperpolarized via dissolution DNP, real-time measurements of their biodistribution and metabolic conversion can be recorded [2, 3]. This technology therefore provides a unique and invaluable tool for probing cellular metabolism in vivo in animal models and in humans in a noninvasive manner [4, 5]. It gives the opportunity to follow and evaluate disease progression and treatment response without requiring ex vivo destructive tissue assays. Numerous preclinical applications have demonstrated the enormous potential of hyperpolarized 13C MRI for in vivo metabolic imaging and several research hospitals across the globe are currently performing studies on patients.

To take advantage of this technology, a dedicated apparatus (hyperpolarizer) has to be placed in the vicinity of the MRI scanner and the hyperpolarized 13C-labeled metabolic substrates need to be produced within a few minutes prior to the injection. This delay as well as the required synchronization between the production and the injection is the major limitation of the method and it restricts the type and number of in vivo metabolic imaging experiments that can be done.

In this lecture, the underlying essential physical concepts as well as suggestions to help assess the potential of the technique within the framework of specific research environments will be presented. An overview of the current state-of-the-art technology will also be given. Explicit examples will be provided to illustrate the power as well as the limitations of hyperpolarized magnetic resonance. Novel methods that open new opportunities to perform hyperpolarized 13C MRI through the circumvention of some of the limitations of the current technology will then be presented. In particular, it will be shown how DNP methods based on non-persistent photo-induced radicals can be designed to dramatically increase the lifetime of the hyperpolarized state by increasing the 13C longitudinal relaxation time of frozen 13C-molecules [6-8].

Acknowledgements

Some of this work is part of a project that has received funding from the European Union’s Horizon 2020 EuropeanResearch Council (ERC Consolidator Grant) under grant agreement no. 682574 (ASSIMILES).