Abstract
History, of course, is difficult to write, if for no other reason, than that it has so many players and so many authors. – P. J. Keating (former Australian Prime Minister) Starting with post-war developments in nuclear magnetic resonance (NMR) a race for stronger and stronger magnetic fields has begun in the 1950s to overcome the inherently low sensitivity of this promising method. Further challenges were larger magnet bores to accommodate small animals and eventually humans. Initially, resistive electromagnets with small pole distances, or sample volumes, and field strengths up to 2.35 T (or 100 MHz 1H frequency) were used in applications in physics, chemistry, and material science. This was followed by stronger and more stable (NbTi based) superconducting magnet technology typically implemented first for small-bore systems in analytical chemistry, biochemistry and structural biology, and eventually allowing larger horizontal-bore magnets with diameters large enough to fit small laboratory animals. By the end of the 1970s, first low-field resistive magnets big enough to accommodate humans were developed and superconducting whole-body systems followed. Currently, cutting-edge analytical NMR systems are available at proton frequencies up to 1 GHz (23.5 T) based on Nb3Sn at 1.9 K. A new 1.2 GHz system (28 T) at 1.9 K, operating in persistent mode but using a combination of low and high temperature multi-filament superconductors is to be released. Preclinical instruments range from small-bore animal systems with typically 600 - 800 MHz (14.1 - 18.8 T) up to 900 MHz (21 T) at 1.9 K. Human whole-body MRI systems currently operate up to 10.5 T. Hybrid combined superconducting and resistive electromagnets with even higher field strength of 45 T dc and 100 T pulsed, are available for material research, of course with smaller free bore diameters. This rather costly development towards higher and higher field strength is a consequence of the inherently low and, thus, urgently needed sensitivity in all NMR experiments. This review particularly describes and compares the developments in superconducting magnet technology and, thus, sensitivity in three fields of research: analytical NMR, biomedical and preclinical research, and human MRI and MRS, highlighting important steps and
Highlights
There have been earlier attempts by physicists to measure the gyromagnetic ratio of various materials using nuclear magnetic resonance (NMR)1, what we call NMR and later magnetic resonance spectroscopy (MRS) and imaging (MRI) today has been commercially available only from the 1950s on
Supporting the booming field of functional magnetic resonance imaging (MRI) including BOLD-based contrast, started in the early 1990s, 3 T systems with strong and fast gradient coils have been developed in parallel and the first “high end” routine MRI systems operating at that field strength became commercially available in 2000
MRI and MRS, higher magnetic flux density (B0) are advantageous for research but not routinely required
Summary
There have been earlier attempts by physicists to measure the gyromagnetic ratio of various materials using nuclear magnetic resonance (NMR)1, what we call NMR and later magnetic resonance spectroscopy (MRS) and imaging (MRI) today has been commercially available only from the 1950s on. Low-resolution NMR systems based on permanent magnets (typically ≤0.5 T or 20 MHz, using various rare earth materials) have been applied to measure relaxation times in fluids, cells and excised animal or human tissue.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
