Rajat K. Ghosh1, Stephen J. Kadlecek1,
Kiarash Emami1, Benjamin M. Pullinger1, Giuseppe Pileio2,
Malcolm H. Levitt2, Nicholas N. Kuzma1,3, Rahim R. Rizi1
1Radiology, University of
Pennsylvania, Philadelphia, PA, United States; 2School of
Chemistry, Southampton University, Southampton, Hampshire, United Kingdom; 3Departments
of Biomedical Engineering & Imaging Sciences, University of Rochester,
Rochester, NY, United States
Development of hyperpolarized MRI tracers is often limited by the longitudinal relaxation rate due to dipolar interactions. It has been previously demonstrated that the effect of dipolar interactions in solution can be removed by storing the nuclear polarization of molecules in long-lived, singlet-like spin states. In the case of doubly-enriched 15N2O storing the polarization of 15N nuclei in the singlet state has been shown to substantially increase their polarization lifetime. The feasibility of utilizing 15N2O as a tracer is investigated by measuring the singlet lifetime of 15N2O when dissolved in a variety of solvents including whole blood. Comparing the singlet lifetime to the T1 relaxation in deuterated and natural solvents sheds light on the mechanism of the singlet state relaxation