Parahydrogen-Induced 13C Hyperpolarizer Using a Flow Guide for Magnetic Field Cycling to Evoke 1H-13C Spin Order Transfer Toward Metabolic MRI

Objective:
The pair-wise addition of parahydrogen, the singlet form of molecular hydrogen, to unsaturated precursors evokes the hyperpolarization of two parahydrogen-derived
¹
H nuclear spins through a process known as parahydrogen-induced polarization (PHIP). Subsequent spin order transfer (SOT) from the
¹
H to the surrounding
¹³
C nuclear spins via magnetic field cycling (MFC) results in substantial signal enhancement in
¹³
C magnetic resonance imaging (MRI). Here, we report the development of a unique PHIP
¹³
C hyperpolarizer system using a flow guide for MFC.
Methods:
The optimal MFC scheme for
¹
H to
¹³
C spin order transfer was quantum-chemically simulated using the J-coupling values of
¹³
C-labeled metabolic tracers. The flow guide system was three-dimensionally designed based on the simulated MFC scheme and pre-measured magnetic field distribution in a zero-field chamber.
Results:
The system efficiently transfers the spin order of hyperpolarized
¹
H to a particular
¹³
C spin when the parahydrogenated tracer passes through the flow guide at a designated flow rate. The
¹³
C MRI signal is enhanced more than 40,000 times in
¹³
C-labeled pyruvate and fumarate, compared to the thermal equilibrium level at 1.5 T, was achieved for conducting
in vivo
metabolic MRI of mice.
Conclusion:
A fully automated PHIP-based
¹³
C polarizer was developed using a unique flow guide to conduct the MFC for
¹
H to
¹³
C SOT. Significance: The PHIP hyperpolarizer with a flow guide can conduct efficient
¹
H-
¹³
C SOT without a MFC magnetic field sweep system and offers a cost-effective alternative to conventional dynamic nuclear polarization.