ADIABATIC SLICE-SELECTIVE EXCITATION FOR SURFACE COILS

A novel RF pulse designed to perform adiabatic slice-selective excitat ion for surface coils (ASSESS) is proposed in which Bo gradient is mod ulated in concert with RF frequency modulation. Within the selected sl ice, the principles of BIR4 pulses are employed to obtain well-defined , pure-phase and self-refocused spin rotation of arbitrary flip angles despite the presence of high B-1 inhomogeneity produced by surface co ils. Outside the slice, advantage is taken of the B-1 field to dephase equilibrium magnetization to achieve slice selection or outer-volume suppression. This scheme should be useful for many localization techni ques. Quaternion analysis of the overall propagator of the proposed pu lse and numerical simulations using Bloch equations are performed. The pulse is tested experimentally on a phantom sample. (C) 1997 Academic Press.