Abstract
Long-lived spin states of hyperpolarized propane-d(6) gas were demonstrated following pairwise addition of parahydrogen gas to propene-d(6) using heterogeneous parahydrogen-induced polarization (HET-PHIP). Hyperpolarized molecules were synthesized using Rh/TiO2 solid catalyst with 1.6 nm Rh nanoparticles. Hyperpolarized (P-H similar to 1%) propane-d(6) was detected at high magnetic field (9.4 T) spectroscopically and by high-resolution 3D gradient-echo MRI (4.7 T) as the gas flowed through the radiofrequency coil with a spatial and temporal resolution of 0.5 X 0.5 X0.5 mm(3) and 17.7 s, respectively. Stopped-flow hyperpolarized propane-d6 gas was also detected at 0.0475 T with an observed nuclear spin polarization of P-H similar to 0.1% and a relatively long lifetime with T-1,(eff) = 6.0 +/- 0.3 s. Importantly, it was shown that the hyperpolarized protons of the deuterated product obtained via pairwise parahydrogen addition could be detected directly at low magnetic field. Importantly, the relatively long low-field T-1,T-eff of HP propane-d(6) gas is not susceptible to paramagnetic impurities as tested by exposure to similar to 0.2 atm oxygen. This long lifetime and nontoxic nature of propane gas could be useful for bioimaging applications including potentially pulmonary low-field MRI. The feasibility of high-resolution low-field 2D gradient-echo MRI was demonstrated with 0.88 X0.88 mm(2) spatial and similar to 0.7 s temporal resolution, respectively, at 0.0475 T.