Indirectly-Detected Heteronuclear MR Spectroscopy & Imaging by Amplified Solvent Proton Signals

Zhao Li¹, Jamie D. Walls¹, Susie Y. Huang¹, Yung-Ya Lin¹

A general spin amplification scheme is developed to enhance the sensitivity of heteronuclear MR spectroscopy and imaging based on dynamic instability of the solvent proton magnetization under collective feedback fields of radiation damping and the distant dipolar field. The heteronuclear solute spins are first detected by the solvent proton spins through various magnetization transfer mechanisms and serve as small input signals to perturb the solvent proton magnetization, which is prepared in an unstable state. The weakly detected signal is then amplified through subsequent nonlinear evolution of the solvent proton magnetization to achieve 10x SNR improvement for 13C NMR and MRI.