Developing a metabolic clearance rate framework as a translational analysis approach for hyperpolarized 13C magnetic resonance imaging

Hyperpolarized carbon-13 magnetic resonance imaging is a promising technique for in vivo metabolic interrogation of alterations between health and disease. This study introduces a formalism for quantifying the metabolic information in hyperpolarized imaging. This study investigated a novel perfusion formalism and metabolic clearance rate (MCR) model in pre-clinical stroke and in the healthy human brain. Simulations showed that the proposed model was robust to perturbations in T-1, transmit B-1, and k(PL). A significant difference in ipsilateral vs contralateral pyruvate derived cerebral blood flow (CBF) was detected in rats (140 +/- 2 vs 89 +/- 6 mL/100 g/min, p < 0.01, respectively) and pigs (139 +/- 12 vs 95 +/- 5 mL/100 g/min, p = 0.04, respectively), along with an increase in fractional metabolism (26 +/- 5 vs 4 +/- 2%, p < 0.01, respectively) in the rodent brain. In addition, a significant increase in ipsilateral vs contralateral MCR (0.034 +/- 0.007 vs 0.017 +/- 0.02/s, p = 0.03, respectively) and a decrease in mean transit time (31 +/- 8 vs 60 +/- 2 s, p = 0.04, respectively) was observed in the porcine brain. In conclusion, MCR mapping is a simple and robust approach to the post-processing of hyperpolarized magnetic resonance imaging.