Broadband proton decoupling for in vivo brain spectroscopy in humans

A new decoupling sequence, PBAR, is described for broadband heteronuclear decoupling in vivo in humans at 1.5T. The sequence uses non-adiabatic, frequency- and amplitude-modulated inversion pulses designed to minimize decoupling sidebands at low applied γB₂ RF field levels and to cover only the narrow range of resonance offsets encountered in practice. The offset dependence of the decoupling efficiency of PBAR is demonstrated and compared to the conventional WALTZ-4 sequence. At the same average power levels, PBAR had slightly reduced bandwidth but significantly less intense decoupling sidebands. Applications of PBAR are shown in vivo in the human brain both for ³¹P and natural abundance ¹³C spectroscopy using volume decoupling coils. The PBAR sequence allows whole brain {¹H}-¹³C decoupling to be performed at 1.5T with a standard head coil within FDA guidelines for RF power deposition.