Chapter 14 - NMR Imaging and Spatially Localized Spectroscopy

Abstract

This chapter outlines the basic principles of the use of nuclear magnetic resonance (NMR) to produce two-dimensional and three-dimensional images. Electrical coils can be used to generate magnetic field gradients in various directions and the strength of each gradient can be used to compensate for inhomogeneities in the applied magnetic field—a process that is called “shimming.” For NMR imaging, a homogeneous magnetic field is obtained across the sample but then it deliberately introduces a linear magnetic field gradient in one or more directions. Many of the pulse techniques are used to create images that show both structure and function in living samples—animal and human and in inanimate objects, such as solid polymers and composite materials. In addition, imaging techniques can be used to permit the observation of ordinary NMR spectra within a localized volume of interest in both living and inanimate samples. For visualization, two-dimensional images are often displayed and analyzed. There are several ways in which such images can be obtained, but the most generally applicable is the use of the 2D (or 3D) NMR methods.