An in vivo automated shimming method taking into account shim current constraints

Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine
H Wen, F A Jaffer

Abstract

Many in vivo imaging techniques require magnetic field homogeneity in the volume of interest. Shim coils of the second and third order spherical harmonics have been used successfully to compensate for complicated field variations caused by the human anatomy itself. The available currents of these coils are invariably limited. In this note we demonstrate that these limits significantly affect the optimal shim condition. We propose an automated in vivo shimming method for arbitrary volumes of interest using 3-dimensional (3D) field maps. This method is a modification of previous works using least-squares criteria. The main difference is that a constrained optimization is performed in vivo under the current limits of the shim coils, which improved the field homogeneity significantly over simple truncations of the least-squares solutions. This shimming method was used with head scans of five normal volunteers on a 4.0 tesla scanner. A fast double-echo sequence was used to obtain field maps, and a new field uniformity measure was derived for this method. The field mapping sequence was tested against a standard single-echo Dixon sequence used by previous investigators, and the stability of the shimming method was tested by repeated s...Continue Reading

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Citations

Apr 12, 2002·Journal of Magnetic Resonance Imaging : JMRI·Robert L GreenmanRobert E Lenkinski
Sep 1, 1996·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·F A JafferS D Wolff
Oct 27, 1997·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·I Marshall, J M Wild
Nov 14, 1997·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·P JezzardD Malonek
Jun 11, 1998·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·S B ReederE R McVeigh
Jan 9, 2008·Magma·Michael Poole, Richard Bowtell
Dec 17, 2002·Journal of Magnetic Resonance·J Michael Tyszka, Adam N Mamelak
Mar 23, 2017·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Paul ChangAnke Henning
Jan 20, 2010·Technology in Cancer Research & Treatment·Mark J HamamuraOrhan Nalcioglu
May 4, 2004·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·L Martyn Klassen, Ravi S Menon
May 25, 2006·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Adil Bashir, Dmitriy A Yablonskiy
Sep 26, 2009·Physics in Medicine and Biology·Miriam R KubachVolker Rasche
Jun 1, 2010·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Philipp KrämerPeter M Jakob
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Apr 10, 2014·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Ariane FillmerAnke Henning
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May 26, 2017·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Sahar NassirpourAnke Henning
Nov 17, 2021·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Yuhang ShiSigne Johanna Vannesjo

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