Single-Shot MRI in parahydrogen hyperpolarized samples

Abstract

The site-specific signal enhancement provided by parahydrogen induced polarization (PHIP) may be combinedwith magnetic resonance imaging (MRI) to study chemical and biomolecular processes. However, imaging ofhydrogen nuclei (1H) is hampered by background signals arising from the presence of thermally polarizednuclei. Additionally, fast imaging sequences are commonly based on multiple radio-frequency pulses, wherethe signals resulting from PHIP oscillate due to the evolution with a -coupling Hamiltonian. In this article, aninnovative imaging scheme for single-scan MRI is presented that effectively detects hyperpolarized componentswhile simultaneously canceling out thermal contributions. This method is based on the quenching of inherentoscillations of PHIP-originated signals due to -couplings during the multipulse sequence and the suppression ofthermal signals by spin dynamics and a tailored restructuring of the -space. A series of numerical simulationson specific two- and three-spin systems serve to support the feasibility of the approach. Furthermore, thistheoretical study demonstrates the potential of combining hyperpolarization and long-lived states (PHIP andLLS) in the selected molecules, which could be seen as a preliminary step towards the development of fastimaging techniques, for example in the field of biomolecular research.