Below is a brief history of the development of magnetic resonance imaging (MRI) and in vivo magnetic resonance spectroscopy (MRS) magnets, followed by a discussion of the medical and life science opportunities enabled by higher field magnets with wider bores and homogeneity than currently exist anywhere in the world. Appendix F provides information on safety and potential health effects of MRI.
Magnetic resonance applications in experimental science started soon after the discovery of proton nuclear magnetic resonance (NMR) in the 1950s. NMR instruments became important for physicists and chemists because the NMR signal carried information about the chemical structure of molecules. The field of MRS is now of major importance, particularly to chemistry (see discussion in Chapter 3). In 1972, chemist Paul Lauterbur of Stony Brook University showed that one can image the spatial distribution of the hydrogen nucleus concentration (mainly water) in objects, and this led to MRI (Lauterbur, 1973). MRI initially and, 10 years later, functional magnetic resonance imaging (fMRI) have become major modalities for research and diagnostic medicine, as well as for animal physiology studies, since the mid-1980s. The growth internationally has been from a few low-field magnets in the United States, Scotland, and England in the mid-1970s to 40,000 installations worldwide in 2012.
The field of NMR spectroscopy being pursued by chemists and physicists for research in molecular structure and dynamics has followed a parallel path of development, but with higher fields and much smaller samples (Figure 4.1).
The initial medical applications used horizontal bore electromagnets with a field strength of 0.04 to 0.15 T in the late 1970s. In the 1980s commercialization was successful for superconducting systems at 0.35 T. In the mid-1980s General Electric marketed worldwide superconducting whole body systems for clinical medicine at 1.5 T. Safety and health effects studies commenced in the late 1970s and continue to the present time while keeping pace with new methods of acquisition of the magnetic resonance signals and the increases in magnetic field strength (Appendix F).
Throughout the development of MRI and MRS, “each substantive increase in field strength has in time led to dramatic improvements in the quality of images and spectra obtainable, and usually to ‘quantum leaps’ in the information available about tissue structure and function [Figure 4.2]. Each major increase in field has also introduced new technical challenges and problems that have required creative scientific and engineering solutions in order to realize the potential to improve image quality.” (Dula, 2010).
The evolution of higher field systems has continued. By 1988 success in development of a whole body 4 T system was reported (Barfuss et al., 1988; Bomsdorf