Abstract

Chemical shift imaging combines the spatial information provided by a conventional nuclear magnetic resonance (NMR) image with the chemical shift spectral information provided by NMR spectroscopy. In order to preserve the chemical shift information and provide a spatial map simultaneously, new NMR imaging methods have been developed. In general, these methods have taken two forms: (a) three-dimensional techniques which add an extra axis of information--chemical shift spectral data--to a planar (2-D) image; and (b) two-dimensional techniques which, in certain circumstances, allow one to use techniques only slightly different from conventional ones to obtain high-resolution images of particular chemical shift species. Each of these methods offers unique challenges to the imager, as well as special advantages. In particular, three-dimensional techniques offer the opportunity to visualize the chemical shift spectra explicitly, while two-dimensional techniques allow for rapid imaging times and high spatial resolution. Most of the work in chemical shift imaging to date has focused on 1H, 31P, and 23Na. The high concentration of water and lipids in biological tissue has made the proton especially amenable to study, and the ability to sample other proton-containing compounds (such as lactate) in the face of high concentration lipid and water is now being explored. The potential use of chemical shift imaging techniques in the research and clinical settings is currently under investigation.