Practical applications of chemical shift imaging.

Methods of spectral localization are briefly reviewed and divided into two classes: those using phase encoding and those using frequency selective RF pulses in a constant gradient. A potentially troubling artifact in the latter case is the spatial misregistration of different compounds which causes serious errors in 31P spectra from smaller regions. Chemical shift imaging (CSI) is presented as a typical example of phase encoding techniques. An analytical expression for the relationship of the signal observed to the true signal (the point spread function) is derived. Examples of CSI in one, two, and three dimensions are used to illustrate the principles of this type of localization.