NMR Microscopy—Fundamentals, Limits and Possible Applications

Abstract

Alongside the numerous applications of NMR spectroscopy to structural elucidation in analytical chemistry, and to biochemical and morphological studies by NMR tomography, NMR microscopy makes possible a whole new range of applications. These include imaging, the investigation of biological objects such as plants and small animals, and also the observation of microscopic structures and structural changes in polymers and ceramics. NMR spectroscopy can also be conducted combinationally as volume-selective spectroscopy, whereby it is possible to spatially resolve the NMR-specific parameters: spin density e, chemical shifts 6, and the relaxation times TI and T z . The numerous well developed methods available make it possible to study dynamic processes by fast imaging with a temporal resolution in milliseconds. This not only allows the imaging of moving objects without incurring movement artefacts but also the measurement of diffusion constants in isotropic and anisotropic diffusion-in the latter case allowing, in principle, the determination of the complete diffusion tensor. The spatially resolved measurement of the relaxation times yields information on molecular mobility and bonding, e.g. the bonding of water, or other solvents, to polymers, the mobility of fluids in polymers or ceramics, or the three-dimensional evaluation of pore size in porous materials. In biomedicine, NMR microscopy allows the observation of growth on the cellular level, the study of embryos, and the development of therapeutic methods in animal experiments. It can lead to a drastic reduction in the number of animal experiments, and in combination with volume-selective spectroscopy gives valuable information on in-vivo metabolism.

Application of Magnetic Resonance Microimaging to the Study of Dental Caries

“…Though MRM revealed a 2-voxel-wide zone around caries, improved resolution would be desirable if caries in enamel is to be studied by MRM. Though Kuhn [1990] has reported imaging soft tissue at a voxel size (10E10E100) µm 3 , partly demineralised tissue presents a greater problem for imaging, and at the present time, routine resolution significantly better than (100 µm) 3 has still to be demonstrated. Existing alternative techniques such as transverse microradiography have better resolution, but the specimen preparation is more demanding.…”

Investigating the Performance of Intensive Mammalian Cell Bioreactor Systems Using Magnetic Resonance Imaging and Spectroscopy

“…Nevertheless, it illustrates very well the basic principles of NMR imaging. Discussion of current methods, which is beyond the scope of this chapter, can be found in the following (Pykett, 1982;Kuhn, 1990, Callaghan, 1991.…”

Non-invasive lipid measurement in living insects using NMR microscopy

“…NMR is a non-destructive and non-invasive technique used to analyse and study the internal morphology of living specimens (Callaghan, 1992). In every living animal, there are many water protons whose NMR-specific parameters, such as the proton spin density, chemical shift, and T1 and T2 relaxation times, can be spatially resolved by magnetic resonance imaging (MRI) (Kuhn, 1990). With the advent of high magnetic field strengths and strong magnetic gradients, spatial resolution of up to one micrometer resolution is achievable (Lee et al, 2001).…”