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Regularized higher‐order in vivo shimming
Author(s) -
Kim DongHyun,
Adalsteinsson Elfar,
Glover Gary H.,
Spielman Daniel M.
Publication year - 2002
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.10267
Subject(s) - shim (computing) , imaging phantom , algorithm , regularization (linguistics) , square root , root mean square , singular value decomposition , mathematics , computer science , physics , artificial intelligence , optics , geometry , medicine , quantum mechanics , erectile dysfunction
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.