| 7 T body MRI: B1 shimming with simultaneous SAR reduction. | |
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MedLine Citation:
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PMID: 17762096 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The high frequency of the radiofrequency (RF) fields used in high field magnetic resonance imaging (MRI) results in electromagnetic field variations that can cause local regions to have a large specific absorption rate (SAR) and/or a low excitation. In this study, we evaluated the use of a B1 shimming technique which can simultaneously improve the B+1 homogeneity and reduce the SAR for whole body imaging at 7 T. Optimizations for four individual anatomies showed a reduction up to 74% of the peak SAR values with respect to a quadrature excitation and a simultaneous improvement of the B+1 homogeneity varying between 39 and 75% for different optimization parameters. The average SAR was reduced with approximately 50% for all optimizations. The optimized phase and amplitude settings from an elliptical phantom model were applied to four realistic human anatomy models to evaluate whether a generic application without prior knowledge of the detailed human anatomy is possible. This resulted in an average improvement of the B+1 homogeneity of 37% and an average reduction of the maximum and average SAR of 50 and 55%, respectively. It can be concluded that this generic method can be used as a simple method to improve the prospects of 7 T body imaging. |
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Authors:
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Bob van den Bergen; Cornelis A T Van den Berg; Lambertus W Bartels; Jan J W Lagendijk |
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Publication Detail:
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Type: Evaluation Studies; Journal Article Date: 2007-08-21 |
Journal Detail:
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Title: Physics in medicine and biology Volume: 52 ISSN: 0031-9155 ISO Abbreviation: Phys Med Biol Publication Date: 2007 Sep |
Date Detail:
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Created Date: 2007-08-31 Completed Date: 2007-11-13 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0401220 Medline TA: Phys Med Biol Country: England |
Other Details:
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Languages: eng Pagination: 5429-41 Citation Subset: IM |
Affiliation:
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Department of Radiotherapy, University Medical Center Utrecht, PO Box 85500, HP Q.00.118, 3508 GA Utrecht, The Netherlands. B.vandenBergen@UMCUtrecht.nl |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Body Burden* Computer Simulation Humans Image Enhancement / methods* Image Interpretation, Computer-Assisted / methods* Magnetic Resonance Imaging / methods* Models, Biological* Radiation Dosage Radiometry / methods Whole-Body Counting |
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