Magnetic field homogeneity: a new approach to orthogonalizing and optimizing shim gradients.
A new approach to optimizing shim coil currents for magnetic resonance magnets is presented. The new approach orthogonalizes the shim coil gradients to allow a simple one-dimensional optimization for each orthogonalized "composite shim." The technique demands no specialized equipment, requiring only the acquisition of simple one-dimensional NMR spectra. Examples from two high-resolution NMR spectrometers are presented, where the shim currents found by the new algorithm provide higher resolution than was obtained by the spectrometer vendor's installation engineers using field-mapping techniques. The examples shown demonstrate the advantages of the technique for high-resolution NMR, but we expect the approach will also find application in a broad variety of areas including imaging and in vivo spectroscopy.
Michal
Carl A
CA
Department of Physics and Astronomy, The University of British Columbia, 6224 Agricultural Rd., Vancouver, BC, Canada V6T 1Z1. michal@physics.ubc.ca
D000465:Algorithms; D003198:Computer Simulation; D004574:Electromagnetic Fields; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D012542:Scattering, Radiation