Rapid, fully automatic, arbitrary-volume in vivo shimming.
MR spectroscopy and many MR imaging methods benefit from a well-shimmed magnet. We have developed a pulse sequence which enables fast and accurate measurement of three-dimensional field maps in vivo, and a data analysis package that allows calculation of shim currents to optimally shim arbitrary selected volumes. A data link to the shim power supply allows automatic update of currents. No intervention by the operator is required. Typical in vivo shimming time is less than 5 min. Performance analysis, phantom, and in vivo results are presented.
Webb
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P
Department of Electrical Engineering, 120 Durand, Stanford University, California 94305.
Macovski
A
A
D001921:Brain / Q000033:anatomy & histology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D008280:Magnetics; D008961:Models, Structural; D008962:Models, Theoretical