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Present and future applications of NMR to medicine and materials science

The phenomenon of nuclear magnetic resonance (NMR) was first observed in the immediate post second -world -war period by two American physicists, working independently: Bloch at Stanford and Purcell at Harvard. Their observations were reported in 1946 in the same volume of Physical Review and led to the joint award of the 1952 Nobel Prize for Physics. Once the details of the interaction had been worked out, and the chemical specificity had been appreciated, a period of instrumentational refinement followed before NMR took its place as arguably the most powerful analytical technique available to the organic chemist. The historical development of NMR and the basis of its analytical power are described in the companion article by Dr. J. Feeney. NMR spectroscopy serves many needs, including routine chemical analysis, determination of protein structures, in situ diagnosis of in -born errors of metabolism and medical imaging. Although the same NMR phenomenon is observed by scientists working in these disparate disciplines, their instrumentational requirements differ widely, and there is often rather little interaction between the different NMR communities. Many specialist international societies have evolved and their annual meetings are extremely well attended in the case of magnetic resonance imaging by typically several thousand participants. The growing diversity of applications, coupled with a unique ability to address certain key contemporary questions (for example the solution structure of biological macromolecules, especially proteins), has made NMR spectrometers the most requested of large scientific instruments. Their high unit cost means that they also account for a substantial fraction of the research budgets of national scientific funding agencies. Of necessity, the scope of this article must be limited. It focuses primarily on magnetic resonance imaging (MRI) and discusses basic principles, present applications and possible development pathways, together with some of the implications these may have for future healthcare policy. The driving force behind the rapid and highly successful development of MRI instrumentation has been, and will remain clinical in