title: Effect of lanthanide ions on dynamic nuclear polarization enhancement and liquid-state T1 relaxation.
abstract: In the dynamic nuclear polarization process, microwave irradiation facilitates exchange of polarization from a radical's unpaired electron to nuclear spins at cryogenic temperatures, increasing polarization by >10,000. Doping samples with Gd(3+) ions further increases the achievable solid-state polarization. However, on dissolution, paramagnetic lanthanide metals can be potent relaxation agents, decreasing liquid-state polarization. Here, the effects of lanthanide metals on the solid and liquid-state magnetic properties of [1-(13)C]pyruvate are studied. The results show that in addition to gadolinium, holmium increases not only the achievable polarization but also the rate of polarization. Liquid-state relaxation studies found that unlike gadolinium, holmium minimally affects T(1). Additionally, results reveal that linear contrast agents dissociate in pyruvic acid, greatly reducing liquid-state T(1). Although macrocyclic agents do not readily dissociate, they yield lower solid-state polarization. Results indicate that polarization with free lanthanides and subsequent chelation during dissolution produces the highest polarization enhancement while minimizing liquid-state relaxation.
authors.affiliation: Department of Medical Physics, University of Wisconsin, Madison, Wisconsin 53705-2275, USA. jwgordon@wisc.edu
authors.forename: Jeremy W
authors.initials: JW
authors.lastname: Gordon
authors.forename: Sean B
authors.initials: SB
authors.lastname: Fain
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Rowland
mesh_terms: D007477:Ions / Q000737:chemistry* / Q000528:radiation effects*; D028581:Lanthanoid Series Elements / Q000737:chemistry* / Q000528:radiation effects*; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000379:methods*; D012996:Solutions / Q000737:chemistry* / Q000528:radiation effects*
chemical_list: D007477:Ions; D028581:Lanthanoid Series Elements; D012996:Solutions