(CSI)
Chemical shift imaging is an extension of MR
spectroscopy, allowing metabolite information to be measured in an extended region and to add the chemical analysis of body tissues to the potential clinical utility of
Magnetic Resonance. The spatial location is
phase encoded and a
spectrum is recorded at each
phase encoding step to allow the
spectra acquisition in a number of volumes covering the whole sample. CSI provides mapping of chemical shifts,
analog to individual spectral lines or groups of lines.
Spatial
resolution can be in one, two or three dimensions, but with long acquisition times od full 3D CSI. Commonly a slice-selected 2D acquisition is used. The chemical composition of each
voxel is represented by
spectra, or as an image in which the
signal intensity depends on the concentration of an individual metabolite. Alternatively frequency-selective pulses excite only a single spectral component.
There are several methods of performing
chemical shift imaging, e.g. the
inversion recovery method,
chemical shift selective imaging sequence,
chemical shift insensitive
slice selective
RF pulse, the
saturation method, spatial and
chemical shift encoded
excitation and quantitative
chemical shift imaging.
See also
Magnetic Resonance Spectroscopy.