Significance: Magnetic resonance imaging (MRI) with hyperpolarized (HP) 13C-labeled redox-sensitive metabolic tracers can provide noninvasive functional imaging biomarkers, reflecting tissue redox state, oxidative stress, and inflammation, among others. The capability to use endogenous metabolites as 13C-enriched imaging tracers without structural modification makes HP 13C MRI a promising tool to evaluate redox state in patients with various diseases. Recent Advances: Recent studies have demonstrated the feasibility of in vivo metabolic imaging of 13C-labeled tracers polarized by parahydrogen-induced polarization techniques, which offer a cost-effective alternative to the more widely used dissolution dynamic nuclear polarization-based hyperpolarizers. Critical Issues: Although the fluxes of many metabolic pathways reflect the change in tissue redox state, they are not functionally specific. In the present review, we summarize recent challenges in the development of specific 13C metabolic tracers for biomarkers of redox state, including that for detecting reactive oxygen species. Future Directions: Applications of HP 13C metabolic MRI to evaluate redox state have only just begun to be investigated. The possibility to gain a comprehensive understanding of the correlations between tissue redox potential and metabolism under different pathological conditions by using HP 13C MRI is promoting its interest in the clinical arena, along with its noninvasive biomarkers to evaluate the extent of disease and treatment response.
Keywords: DNP; hyperpolarized 13C MRI; inflammation; oxidative stress; parahydrogen; redox state.