Spectroscopic spatial localization based on B1 gradients is generally performed as an amplitude-modulated experiment using a single surface coil, with a consequent loss in signal-to-noise ( S N) ratio. The phase-modulated implementation of such experiments with a single surface coil requires the ability to apply both B1-dependent rotations and B1-independent 90° plane rotations using the same surface coil. It is demonstrated that this is now possible using adiabatic plane-rotation pulses. These pulses can execute a plane rotation of any angle despite the presence of large B1 inhomogeneities; therefore, they can be used to perform a 90° plane rotation throughout the sensitive volume of a surface coil. A new phase-modulated, spatial-localization experiment based on B0 and B1 gradients (RAPP-ISIS) is introduced. It is shown, using phantom and in vivo, intact animal studies, that the technique provides excellent spectroscopic localization and the expected gain in S N compared to its amplitude-modulated analogue.
Bibliographical noteFunding Information:
* This work was supported by NIH Grants HL33600, HL32247, AM 34931, CA50703 and the Vikings Children’s Fund. # Present address: Department of Pathology, University of Cincinnati, Cincinatti, Ohio 45267-07 14. * * To whom correspondence should be addressed at the Center for Magnetic Resonance Research.