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MAGMA. 2008 Mar;21(1-2):31-40. doi: 10.1007/s10334-007-0102-2. Epub 2008 Jan 8.

Volume parcellation for improved dynamic shimming.

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  • 1Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University Park, Nottingham, NG7 2RD, UK.

Abstract

INTRODUCTION:

The need for a homogeneous magnetic field in magnetic resonance imaging is well established, especially at high static magnetic field strengths where susceptibility-induced image distortions and signal losses become excessively large. Dynamic shim updating, where the optimal set of shim currents is applied for each slice during a multi-slice acquisition, has been shown to improve magnetic field homogeneity to a greater extent than conventional global shimming.

METHODS:

Here, in an initial feasibility study, we show via simulation that improved efficacy of shimming can be achieved by using the novel parcellated dynamic shimming method.

RESULTS:

The results of these simulations indicate that parcellated dynamic shimming based on just linear shim terms can perform approximately as well as slice-based dynamic shimming with up to third-order shim terms.

CONCLUSIONS:

This work shows that the effective magnetic field inhomogeneity can be further reduced if shimming and image data acquisition are sequentially performed over a series of compact, cuboidal sub-volumes rather than planes. Further work is needed to develop an imaging approach that can be used for the optimal implementation of parcellated dynamic shimming.

PMID:
18180969
[PubMed - indexed for MEDLINE]
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