Effect of RF coil excitation on field inhomogeneity at ultra high fields: a field optimized TEM resonator
In this work, computational methods were utilized to optimize the field produced by the transverse electromagnetic (TEM) resonator in the presence of the human head at 8 Tesla. Optimization was achieved through the use of the classical finite difference time domain (FDTD) method and a TEM resonator...
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| Veröffentlicht in: | Magnetic resonance imaging 2001-12, Vol.19 (10), p.1339-1347 |
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| creator | Ibrahim, Tamer S Lee, Robert Baertlein, Brian A Abduljalil, Amir M Zhu, Hui Robitaille, Pierre-Marie L |
| description | In this work, computational methods were utilized to optimize the field produced by the transverse electromagnetic (TEM) resonator in the presence of the human head at 8 Tesla. Optimization was achieved through the use of the classical finite difference time domain (FDTD) method and a TEM resonator loaded with an anatomically detailed human head model with a resolution of 2 mm × 2 mm × 2 mm. The head model was developed from 3D MR images. To account for the electromagnetic interactions between the coil and the tissue, the coil and the head were treated as a single system at all the steps of the model including, numerical tuning and excitation. In addition to 2, 3, 4, 6, and 10-port excitations, an antenna array concept was utilized by driving all the possible ports (24) of a 24-strut TEM resonator. The results show that significant improvement in the circularly polarized component of the transverse magnetic field could be obtained when using multiple ports and variable phase and fixed magnitude, or variable phase and variable magnitude excitations. |
| doi_str_mv | 10.1016/S0730-725X(01)00404-0 |
| format | Article |
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Optimization was achieved through the use of the classical finite difference time domain (FDTD) method and a TEM resonator loaded with an anatomically detailed human head model with a resolution of 2 mm × 2 mm × 2 mm. The head model was developed from 3D MR images. To account for the electromagnetic interactions between the coil and the tissue, the coil and the head were treated as a single system at all the steps of the model including, numerical tuning and excitation. In addition to 2, 3, 4, 6, and 10-port excitations, an antenna array concept was utilized by driving all the possible ports (24) of a 24-strut TEM resonator. The results show that significant improvement in the circularly polarized component of the transverse magnetic field could be obtained when using multiple ports and variable phase and fixed magnitude, or variable phase and variable magnitude excitations.</description><identifier>ISSN: 0730-725X</identifier><identifier>EISSN: 1873-5894</identifier><identifier>DOI: 10.1016/S0730-725X(01)00404-0</identifier><identifier>PMID: 11804762</identifier><identifier>CODEN: MRIMDQ</identifier><language>eng</language><publisher>New York, NY: Elsevier Inc</publisher><subject>B1 field ; Biological and medical sciences ; Electromagnetic Fields ; Head - anatomy & histology ; Humans ; Investigative techniques, diagnostic techniques (general aspects) ; Magnetic Resonance Imaging - methods ; Medical sciences ; Miscellaneous. Technology ; Nervous system ; Numerical optimization ; Radiodiagnosis. Nmr imagery. 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Optimization was achieved through the use of the classical finite difference time domain (FDTD) method and a TEM resonator loaded with an anatomically detailed human head model with a resolution of 2 mm × 2 mm × 2 mm. The head model was developed from 3D MR images. To account for the electromagnetic interactions between the coil and the tissue, the coil and the head were treated as a single system at all the steps of the model including, numerical tuning and excitation. In addition to 2, 3, 4, 6, and 10-port excitations, an antenna array concept was utilized by driving all the possible ports (24) of a 24-strut TEM resonator. The results show that significant improvement in the circularly polarized component of the transverse magnetic field could be obtained when using multiple ports and variable phase and fixed magnitude, or variable phase and variable magnitude excitations.</description><subject>B1 field</subject><subject>Biological and medical sciences</subject><subject>Electromagnetic Fields</subject><subject>Head - anatomy & histology</subject><subject>Humans</subject><subject>Investigative techniques, diagnostic techniques (general aspects)</subject><subject>Magnetic Resonance Imaging - methods</subject><subject>Medical sciences</subject><subject>Miscellaneous. Technology</subject><subject>Nervous system</subject><subject>Numerical optimization</subject><subject>Radiodiagnosis. Nmr imagery. 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Technology</topic><topic>Nervous system</topic><topic>Numerical optimization</topic><topic>Radiodiagnosis. Nmr imagery. Nmr spectrometry</topic><topic>TEM Resonator</topic><topic>Time Factors</topic><topic>Ultra high field</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Ibrahim, Tamer S</creatorcontrib><creatorcontrib>Lee, Robert</creatorcontrib><creatorcontrib>Baertlein, Brian A</creatorcontrib><creatorcontrib>Abduljalil, Amir M</creatorcontrib><creatorcontrib>Zhu, Hui</creatorcontrib><creatorcontrib>Robitaille, Pierre-Marie L</creatorcontrib><collection>Pascal-Francis</collection><collection>Medline</collection><collection>MEDLINE</collection><collection>MEDLINE (Ovid)</collection><collection>MEDLINE</collection><collection>MEDLINE</collection><collection>PubMed</collection><collection>CrossRef</collection><collection>MEDLINE - Academic</collection><jtitle>Magnetic resonance imaging</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Ibrahim, Tamer S</au><au>Lee, Robert</au><au>Baertlein, Brian A</au><au>Abduljalil, Amir M</au><au>Zhu, Hui</au><au>Robitaille, Pierre-Marie L</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Effect of RF coil excitation on field inhomogeneity at ultra high fields: a field optimized TEM resonator</atitle><jtitle>Magnetic resonance imaging</jtitle><addtitle>Magn Reson Imaging</addtitle><date>2001-12-01</date><risdate>2001</risdate><volume>19</volume><issue>10</issue><spage>1339</spage><epage>1347</epage><pages>1339-1347</pages><issn>0730-725X</issn><eissn>1873-5894</eissn><coden>MRIMDQ</coden><abstract>In this work, computational methods were utilized to optimize the field produced by the transverse electromagnetic (TEM) resonator in the presence of the human head at 8 Tesla. Optimization was achieved through the use of the classical finite difference time domain (FDTD) method and a TEM resonator loaded with an anatomically detailed human head model with a resolution of 2 mm × 2 mm × 2 mm. The head model was developed from 3D MR images. To account for the electromagnetic interactions between the coil and the tissue, the coil and the head were treated as a single system at all the steps of the model including, numerical tuning and excitation. In addition to 2, 3, 4, 6, and 10-port excitations, an antenna array concept was utilized by driving all the possible ports (24) of a 24-strut TEM resonator. 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| source | MEDLINE; Elsevier ScienceDirect Journals Complete |
| subjects | B1 field Biological and medical sciences Electromagnetic Fields Head - anatomy & histology Humans Investigative techniques, diagnostic techniques (general aspects) Magnetic Resonance Imaging - methods Medical sciences Miscellaneous. Technology Nervous system Numerical optimization Radiodiagnosis. Nmr imagery. Nmr spectrometry TEM Resonator Time Factors Ultra high field |
| title | Effect of RF coil excitation on field inhomogeneity at ultra high fields: a field optimized TEM resonator |
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