Local and whole‐body SAR in UHF body imaging: Implications for SAR matrix compression.
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| Title: | Local and whole‐body SAR in UHF body imaging: Implications for SAR matrix compression. |
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| Authors: | Fiedler, Thomas M.1 (AUTHOR) t.fiedler@dkfz-heidelberg.de, Ladd, Mark E.1,2,3,4 (AUTHOR), Orzada, Stephan1,2 (AUTHOR) |
| Source: | Magnetic Resonance in Medicine. Feb2025, Vol. 93 Issue 2, p842-849. 8p. |
| Subjects: | Antenna arrays, Transmitting antennas, Human body, Birdcages, Matrices (Mathematics) |
| Abstract: | Purpose: Transmit arrays for body imaging have characteristics of both volume and local transmit coils. This study evaluates two specific absorption rate (SAR) aspects, local and whole‐body SAR, of arrays for body imaging at 7 T and also for a 3 T birdcage. Methods: Simulations were performed for six antenna arrays at 7 T and one 3 T birdcage. Local SAR matrices and the whole‐body SAR matrix were computed and evaluated with random shims. A set of reduced local SAR matrices was determined by removing all matrices dominated by the whole‐body SAR matrix. Results: The results indicate that all RF transmit coils for body imaging in this study are constrained by the local SAR limit. The ratio between local and whole‐body SAR is nevertheless smaller for arrays with large FOV, as these arrays also expose a larger part of the human body. By using the whole‐body SAR matrix, the number of local SAR matrices can be reduced (e.g., 33.3% matrices remained for an 8‐channel local array and 89.7% for a 30‐channel remote array; 12.1% for the 3 T birdcage). Conclusion: For transmit antenna arrays used for body imaging at 7 T as well as for the 3 T birdcage, all evaluated cases show that the local SAR limit was reached before reaching the whole‐body SAR limit. Nevertheless, the whole‐body SAR matrix can be used to reduce the number of local SAR matrices, which is important to reduce memory and computing time for a virtual observation points (VOP) compression. This step can be included as a pre‐compression prior to a VOP compression. [ABSTRACT FROM AUTHOR] |
| Copyright of Magnetic Resonance in Medicine is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
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| Items | – Name: Title Label: Title Group: Ti Data: Local and whole‐body SAR in UHF body imaging: Implications for SAR matrix compression. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Fiedler%2C+Thomas+M%2E%22">Fiedler, Thomas M.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> t.fiedler@dkfz-heidelberg.de</i><br /><searchLink fieldCode="AR" term="%22Ladd%2C+Mark+E%2E%22">Ladd, Mark E.</searchLink><relatesTo>1,2,3,4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Orzada%2C+Stephan%22">Orzada, Stephan</searchLink><relatesTo>1,2</relatesTo> (AUTHOR) – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Magnetic+Resonance+in+Medicine%22">Magnetic Resonance in Medicine</searchLink>. Feb2025, Vol. 93 Issue 2, p842-849. 8p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Antenna+arrays%22">Antenna arrays</searchLink><br /><searchLink fieldCode="DE" term="%22Transmitting+antennas%22">Transmitting antennas</searchLink><br /><searchLink fieldCode="DE" term="%22Human+body%22">Human body</searchLink><br /><searchLink fieldCode="DE" term="%22Birdcages%22">Birdcages</searchLink><br /><searchLink fieldCode="DE" term="%22Matrices+%28Mathematics%29%22">Matrices (Mathematics)</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Purpose: Transmit arrays for body imaging have characteristics of both volume and local transmit coils. This study evaluates two specific absorption rate (SAR) aspects, local and whole‐body SAR, of arrays for body imaging at 7 T and also for a 3 T birdcage. Methods: Simulations were performed for six antenna arrays at 7 T and one 3 T birdcage. Local SAR matrices and the whole‐body SAR matrix were computed and evaluated with random shims. A set of reduced local SAR matrices was determined by removing all matrices dominated by the whole‐body SAR matrix. Results: The results indicate that all RF transmit coils for body imaging in this study are constrained by the local SAR limit. The ratio between local and whole‐body SAR is nevertheless smaller for arrays with large FOV, as these arrays also expose a larger part of the human body. By using the whole‐body SAR matrix, the number of local SAR matrices can be reduced (e.g., 33.3% matrices remained for an 8‐channel local array and 89.7% for a 30‐channel remote array; 12.1% for the 3 T birdcage). Conclusion: For transmit antenna arrays used for body imaging at 7 T as well as for the 3 T birdcage, all evaluated cases show that the local SAR limit was reached before reaching the whole‐body SAR limit. Nevertheless, the whole‐body SAR matrix can be used to reduce the number of local SAR matrices, which is important to reduce memory and computing time for a virtual observation points (VOP) compression. This step can be included as a pre‐compression prior to a VOP compression. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Magnetic Resonance in Medicine is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1002/mrm.30306 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 8 StartPage: 842 Subjects: – SubjectFull: Antenna arrays Type: general – SubjectFull: Transmitting antennas Type: general – SubjectFull: Human body Type: general – SubjectFull: Birdcages Type: general – SubjectFull: Matrices (Mathematics) Type: general Titles: – TitleFull: Local and whole‐body SAR in UHF body imaging: Implications for SAR matrix compression. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Fiedler, Thomas M. – PersonEntity: Name: NameFull: Ladd, Mark E. – PersonEntity: Name: NameFull: Orzada, Stephan IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 02 Text: Feb2025 Type: published Y: 2025 Identifiers: – Type: issn-print Value: 07403194 Numbering: – Type: volume Value: 93 – Type: issue Value: 2 Titles: – TitleFull: Magnetic Resonance in Medicine Type: main |
| ResultId | 1 |
