Christine Pepke Gunnarsson

PhD project by Christine Pepke Gunnarsson

Name: Christine Pepke Gunnarsson
Project Title: Dynamic Nuclear Polarization with Labile Radicals
Group: 
Center for Magnetic Resonance
Supervisor:
Jan Ardenkjær-Larsen, Andrea Capozzi and Magnus Karlsson

Project Description:
Dissolution Dynamic Nuclear Polarization (dDNP), the transfer of the electron spin polarization to the nuclear spins using microwave radiation, is an efficient method to hyperpolarize nuclear spins and achieving dramatically enhanced magnetic resonance (MR) signals.

However, the nuclear spin polarization decays fast due to the electron spins, when the sample is moved to lower magnetic field and non cryogenic temperatures. Therefore, the dissolution is performed inside the polarizer, which means that currently a polarizer is needed at every MR spectrometer. A solution to this challenge is to use photo induced labile radicals which makes it possible to keep the polarization of the nuclei for a longer time. Irradiating radical precursors with UV light at cryogenic temperatures generates radicals that can be used to polarize substrates through DNP. The radicals are persistent at cryogenic temperatures, but annihilates if the sample temperature increases above 190 K, which is below the samples melting point (285 K). In this way, the radicals can be thermally annihilated while the sample is still a solid and the nuclear polarization can then be maintained as the solid sample is extracted from the polarizer, opening for the possibility of transportation of the hyperpolarized sample. 

The purpose of the project is to gain an understanding of the photo induced radical formation, aiming at improving the radical yield and obtaining radicals with optimal spectral properties for dDNP. The project will also examine the physico-chemical properties of the thermal annihilation of the radicals and investigate the relaxation mechanisms of the polarized sample.

Perspective:
Thanks to dDNP, polarization enhancements of up to 10.000 compared to the thermal equilibrium have been reported, and with the current achievements, hyperpolarization of nuclear spins opens for the possibility of faster and more accurate cancer diagnosis through MR imaging using the hyperpolarized sample as contrast agent. The possibility of transporting and storing the hyperpolarized sample will enable hyperpolarized MR imaging performed remotely from the polarizer, an achievement that will decrease the involved costs significantly. 

Kontakt

Christine Pepke Gunnarsson
Ph.d.-studerende
DTU Sundhedsteknologi

Kontakt

Jan Henrik Ardenkjær-Larsen
Sektionsleder, Professor
DTU Sundhedsteknologi
45 25 39 18

Kontakt

Andrea Capozzi
Postdoc
DTU Sundhedsteknologi

Kontakt

Magnus Karlsson
Seniorforsker
DTU Sundhedsteknologi
45 25 36 77