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Regularized higher-order in vivo shimming

✍ Scribed by Dong-Hyun Kim; Elfar Adalsteinsson; Gary H. Glover; Daniel M. Spielman

Publisher
John Wiley and Sons
Year
2002
Tongue
English
Weight
882 KB
Volume
48
Category
Article
ISSN
0740-3194

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✦ Synopsis

Abstract

A regularized algorithm is presented for localized in vivo shimming. The technique uses first‐ (X,Y,Z), second‐ (Z^2^, ZX, ZY, X^2^‐Y^2^, XY), and third‐order (Z^3^) shim coils, and is robust when applied to arbitrarily‐shaped, as well as off‐center, regions of interest (ROIs). A single‐shot spiral pulse sequence is used for rapid field map acquisition, and a least‐squares calculation of the shim currents is performed to minimize the root‐mean‐square (RMS) value of the B~0~ inhomogeneity over a user‐selected ROI. The use of a singular value decomposition (SVD) in combination with a regularization algorithm significantly improves the numerical stability of the least‐squares fitting procedure. The fully automated shimming package is implemented on a 3 T GE Signa system and its robust performance is demonstrated in phantom and in vivo studies. Magn Reson Med 48:715–722, 2002. © 2002 Wiley‐Liss, Inc.

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