Increasing 15N and 13C polarization in parahydrogen-induced polarization relayed via proton exchange.

Motivation: To enhance hyperpolarization for MRI, focusing on cost-effective and broadly applicable parahydrogen-induced polarization relayed via proton exchange (PHIP-X). Goal(s): To find optimal parameters in PHIP-X to maximize ¹³C and ¹⁵N polarization levels. Approach: Our approach was to simulate quantum spin dynamics to study the effects of exchange rates, magnetic field cycling, proton relaxation and J-coupling networks. Results: Optimal conditions are exchange rate of 200 s⁻¹, magnetic fields below 10 nT, labile proton relaxation times above 0.1 s and matching of J-couplings of labile protons. Polarizations up to 24% for ¹³C and 14% for ¹⁵N were found. Impact: The findings pave the way to develop a pH2-based method that can strongly polarize 13C and 15N nuclei of a wide range of biomolecules playing an important role in metabolic MR imaging. Scientists may try to use new imaging agents.