New PhD student working on Dynamic Nuclear Polarization with labile radicals

Friday 12 Jan 18


Christine Pepke Gunnarsson
PhD student
DTU Health Tech


Jan Henrik Ardenkjær-Larsen
Head of Sections, Professor
DTU Health Tech
+45 45 25 39 18


Andrea Capozzi
DTU Health Tech


Magnus Karlsson
Senior Researcher
DTU Health Tech
+45 45 25 36 77
Christine Pepke Gunnarsson has been employed as a PhD student at CMR’s Center of Excellence HYPERMAG

Christine will work on the project Dynamic Nuclear Polarization with Labile Radicals

Hyperpolarized Magnetic Resonance Imaging is an novel modality with unique capabilities for real-time non-invasive anatomical, functional and metabolic imaging, due to its enhancement of the Magnetic Resonance signal with a factor of more than 100,000 in vivo. 

The most general and versatile method to hyperpolarize nuclear spins is by dissolution Dynamic Nuclear Polarization (dDNP). Strong nuclear spins polarization is obtained in high magnetic field (several Tesla) and at low temperature (a few Kelvin). The main limitation of the method is that  the nuclear spin polarization relaxes in seconds, or less, if the solid sample is taken to lower magnetic field or higher temperatures. It is currently not feasible to withdraw the sample from the polarizer and perform the dissolution at a remote location of use. This means that expensive infrastructure doe polarization is needed at every site of use. 

The generation of labile radicals in the solid at low temperature may be a way to overcome the problem. It has recently been demonstrated that non-persistent radicals can be used to polarize substrates via dDNP. Upon UV-irradiation at cryogenic temperatures, radicals are generated that are persistent at liquid nitrogen temperature, but annihilate if the sample temperature increases above 190 K, which is still below the samples melting point (285 K). 

Christine’s PhD project aims to provide a deeper understanding of the mechanism of photo-induced radical formation. The purpose is to improve radical yield and obtain radicals with optimal spectral properties for DNP. The PhD project will also investigate the physico-chemical properties of the annihilation of the radical above a certain temperature, but below the melting point of the sample. The project will establish conditions that allow the hyperpolarized solid sample to be withdrawn from the polarizer and into a transport container as well as establishing practical conditions, magnetic field and temperature, for transportation of the hyperpolarized solid sample. 

This will make hyperpolarized MRI possible performed remotely from polarizers possible and bring associated costs down, unleashing a more widespread use of the modality's superior capabilities.

Christine holds a MSc in Physics from Copenhagen University.

Christine’s project is funded by Independent Research Fund Denmark as part of the "Spin Bank" – turning electron spin on and off project (File No. 7017-00322B). 

HYPERMAG’s Center Leader and CMR Group Leader, Professor Jan Henrik Ardenkjær-Larsen is Christine’s main Supervisor. Co-supervisors are Postdoc Andrea Capozzi and Senior Researcher Magnus Karlsson. 

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26 FEBRUARY 2020