Adiabatic Slice-Selective Excitation for Surface Coils

Abstract

A novel RF pulse designed to performadiabaticslice-selectiveexcitation forsurface coils(ASSESS) is proposed in whichB₀gradient is modulated in concert with RF frequency modulation. Within the selected slice, 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 highB₁inhomogeneity produced by surface coils. Outside the slice, advantage is taken of theB₁field to dephase equilibrium magnetization to achieve slice selection or outer-volume suppression. This scheme should be useful for many localization techniques. Quaternion analysis of the overall propagator of the proposed pulse and numerical simulations using Bloch equations are performed. The pulse is tested experimentally on a phantom sample.