ADIABATIC SLICE-SELECTIVE RF PULSES AND A SINGLE-SHOT ADIABATIC LOCALIZATION PULSE SEQUENCE

The localization quality of frequency-selective adiabatic radio frequency (rf) pulses is substantially less affected by rf inhomogeneity than is the localization of amplitude-modulated pulses. For this reason, adiabatic pulses are popular for use in experiments carried out with rf coils that produce inhomogeneous rf fields. Starting with the Schrodinger equation, the Bloch equations are derived, neglecting relaxation. The adiabatic principle is introduced, and it is demonstrated that accurate adiabatic localization is possible with simple schemes for amplitude and frequency modulation. Adiabatic pulses perform well only in an rf amplitude range limited by a lower and an upper bound. Phase-compensated, slice-selective adiabatic 2 pi pulses are used in a variant of the single-shot localization method, SADLOVE, for which a theoretical quantitative model of the localization performance is derived. A simple variant of the VERSE method to reduce the rf pulse energy of adiabatic pulses is presented. (C) 1995 John Wiley & Sons, Inc.