In vivo phosphorus polarization transfer and decoupling from protons in three‐dimensional localized nuclear magnetic resonance spectroscopy of human brain

Abstract

Refocused insensitive nucleus enhancement by polarization transfer (RINEPT) from protons (¹H) to a J‐coupled phosphorus (³¹P) has been incorporated into three‐dimensional (3D) chemical‐shift‐imaging (CSI) sequence on a clinical imager. The technique is demonstrated on a phantom and in in vivo human brain. The polarization‐transfer efficiency (∼1.2) is lower than the theoretical maximum of γ¹H/γ³¹P≈ 2.4 resulting from ¹H‐¹H homonuclear J couplings of similar magnitude competing with the ¹H →³¹P transfer. Nevertheless, compared with direct ³¹P Ernst‐angle excitation, signal gains of up to × 1.8 were obtained mainly as a result of T¹ differences between ³¹P and the ¹H. Spectral interpretation is simplified by editing out all non‐proton‐coupled ³¹P signals. The duration, ∼50 min, and power deposition, ∼1 W · kg⁻¹, make the application suitable for human studies.