Chemical-shift imaging.

The echo-planar shift mapping (EPSM) technique, a variant of echo-planar imaging (EPI), is evaluated with theoretical studies using computer simulations and with experimental studies using fluorine resonances in phantoms. In situations where the signal-to-noise ratio permits, it is shown that EPSM can produce in a few seconds chemical-shift spectra at all points in a specified spin-density image corresponding to a selected slice. Applications of this technique are likely to be for proton and fluorine chemical-shift measurements and rapid studies of magnetic field inhomogeneities produced by magnet non-alignment and field shifts around magnetic materials.