Abstract
Parahydrogen induced polarization was employed to prepare a relatively long-lived correlated nuclear spin state between methylene and methyl protons in propane gas. Conventionally, such states are converted into a strong NMR signal enhancement by transferring the reaction product to a high magnetic field in an adiabatic longitudinal transport after dissociation engenders net alignment (ALTADENA) experiment. However, the relaxation time T-1 of approximate to 0.6s of the resulting hyperpolarized propane is too short for potential biomedical applications. The presented alternative approach employs low-field MRI to preserve the initial correlated state with a much longer decay time T-LLSS=(4.7 +/- 0.5)s. While the direct detection at low-magnetic fields (e.g. 0.0475T) is challenging, we demonstrate here that spin-lock induced crossing (SLIC) at this low magnetic field transforms the long-lived correlated state into an observable nuclear magnetization suitable for MRI with sub-millimeter and sub-second spatial and temporal resolution, respectively. Propane is a non-toxic gas, and therefore, these results potentially enable low-cost high-resolution high-speed MRI of gases for functional imaging of lungs and other applications.