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| Meiboom–Gill | |
|---|---|
| Name | Meiboom–Gill |
| Field | Magnetic resonance |
Meiboom–Gill is a pulse sequence used in nuclear magnetic resonance and magnetic resonance imaging to measure transverse relaxation and refocus dephasing while reducing systematic errors. Developed to improve robustness against pulse imperfections and static field inhomogeneities, it is widely used in spectroscopy and imaging experiments conducted on instruments by Ernst Ruska-era laboratories and modern facilities such as Institut Laue–Langevin, Max Planck Society, and National Institutes of Health. Its adoption spans groups at University of Oxford, Massachusetts Institute of Technology, Harvard University, Stanford University, and industrial researchers at Siemens, Philips, and GE Healthcare.
The sequence was introduced to address shortcomings observed in earlier echo techniques like the Hahn echo and implementations deployed at centers including Bell Labs, Los Alamos National Laboratory, and Lawrence Berkeley National Laboratory. It emerged alongside advances from researchers affiliated with Niels Bohr Institute, Columbia University, Princeton University, and California Institute of Technology who studied spin dynamics and relaxation phenomena. The method built on theoretical frameworks developed by pioneers such as Felix Bloch, Edward Purcell, Isidor Rabi, and experimental practice refined in groups at Brookhaven National Laboratory and Argonne National Laboratory. Early demonstrations leveraged spectrometers from manufacturers like Bruker and Varian and were discussed at conferences organized by International Society of Magnetic Resonance and American Physical Society meetings.
The sequence consists of an initial 90° pulse followed by a train of refocusing pulses, implemented in spectrometers and imagers sold by Bruker, Varian, Agilent Technologies, and Rohde & Schwarz. Practitioners at University of Cambridge, University of California, Berkeley, Yale University, and University of Tokyo use phase cycling strategies developed in collaboration with groups from ETH Zurich and University of Geneva. Typical implementations use a 90° pulse about the x-axis and subsequent 180° pulses with phase alternation about the y-axis, a scheme that contrasts with simple 180° trains used in sequences reported at MIT Lincoln Laboratory and Los Alamos Scientific Laboratory. Vendors such as Siemens Healthineers provide sequence blocks in scanners at hospitals like Mayo Clinic, Cleveland Clinic, and Johns Hopkins Hospital.
The robustness of the sequence is explained by spin Hamiltonian analyses and average Hamiltonian theory developed by theorists at Cornell University, University of Illinois Urbana-Champaign, University of Pennsylvania, and Rice University. Mathematical treatments reference work by Albert Overhauser, Claude Shannon-adjacent signal processing groups, and formalism used in textbooks from authors affiliated with Oxford University Press and Cambridge University Press publishers. The mechanism relies on phase cycling to cancel pulse error accumulations, an idea related to developments by Ernst Ising-associated researchers and echoed in studies from Los Alamos and Princeton Plasma Physics Laboratory on coherent control. Theoretical modeling often uses computational packages from MathWorks and simulations run on clusters at Lawrence Livermore National Laboratory and supercomputers at National Center for Supercomputing Applications.
Laboratory implementations require calibration routines and hardware considerations addressed by engineering groups at Honeywell, Lockheed Martin, and Raytheon Technologies. Experimentalists at Scripps Research, Cold Spring Harbor Laboratory, Howard Hughes Medical Institute, and Fred Hutchinson Cancer Research Center optimize pulse shapes using tools from National Institute of Standards and Technology and pulse programmers developed at MITRE Corporation. Temperature control and sample handling protocols are informed by standards from American National Standards Institute and collaborations with core facilities at University College London and Imperial College London. High-field experiments leverage magnets from Oxford Instruments and Toshiba-supplied systems utilized in clinical studies at Massachusetts General Hospital and Stanford Health Care.
Several modifications extend the original protocol, including Carr–Purcell–Meiboom–Gill-inspired adaptations used in multi-echo sequences in publications from Nature Communications, Science Advances, and Physical Review Letters. Researchers at University of Zurich, ETH Zurich, Karolinska Institutet, and Institut Curie have combined the sequence with adiabatic pulses, composite pulses, and shaped pulses derived from work at Los Alamos and Argonne. Multi-dimensional experiments incorporating this refocusing method are reported by teams at Johns Hopkins University, UCSF, Duke University, and University of Michigan for studies in metabolomics and diffusion measurements. Hybrid approaches pair the sequence with gradient-echo modules in systems by Philips Healthcare and advanced encoding strategies developed at EPFL and KTH Royal Institute of Technology.
The sequence is applied in spectroscopy to measure transverse relaxation times in samples studied at Scripps Institution of Oceanography, Smithsonian Institution, and Natural History Museum, London. Clinical and preclinical imaging applications occur in studies at Karolinska University Hospital, Vall d'Hebron University Hospital, and research centers across National Institutes of Health institutes. Industrial research uses include polymer characterization at BASF, oil exploration research sponsored by Schlumberger, and food science projects at Nestlé and Kraft Foods. The method supports investigations in structural biology by consortia associated with European Molecular Biology Laboratory, Wellcome Trust, and Howard Hughes Medical Institute.
Limitations arise from pulse imperfections, hardware nonlinearities, and relaxation pathways documented by investigators at Los Alamos National Laboratory, Brookhaven National Laboratory, and National Institute of Standards and Technology. Errors can stem from imperfect 180° pulses, B1 inhomogeneity present in systems from Siemens and Philips, and diffusion effects discussed in literature from American Chemical Society and Royal Society of Chemistry journals. Mitigation strategies were developed by groups at University of Basel, ETH Zurich, and Weizmann Institute of Science employing composite pulses and calibration routines shared at conferences hosted by International Society of Magnetic Resonance.
Category:Magnetic resonance techniques