Comparison of simulated parallel transmit body arrays at 3 T using excitation uniformity, global SAR, local SAR, and power efficiency metrics
Purpose We compare the performance of eight parallel transmit (pTx) body arrays with up to 32 channels and a standard birdcage design. Excitation uniformity, local specific absorption rate (SAR), global SAR, and power metrics are analyzed in the torso at 3 T for radiofrequency (RF)-shimming and 2...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | en_US |
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Wiley Blackwell
2017
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| Online Access: | http://hdl.handle.net/1721.1/110707 https://orcid.org/0000-0002-7637-2914 |
| _version_ | 1826212809259614208 |
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| author | Guérin, Bastien Gebhardt, Matthias Serano, Peter Adalsteinsson, Elfar Hamm, Michael Pfeuffer, Josef Nistler, Juergen Wald, Lawrence L. |
| author2 | Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science |
| author_facet | Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science Guérin, Bastien Gebhardt, Matthias Serano, Peter Adalsteinsson, Elfar Hamm, Michael Pfeuffer, Josef Nistler, Juergen Wald, Lawrence L. |
| author_sort | Guérin, Bastien |
| collection | MIT |
| description | Purpose
We compare the performance of eight parallel transmit (pTx) body arrays with up to 32 channels and a standard birdcage design. Excitation uniformity, local specific absorption rate (SAR), global SAR, and power metrics are analyzed in the torso at 3 T for radiofrequency (RF)-shimming and 2-spoke excitations.
Methods
We used a fast cosimulation strategy for field calculation in the presence of coupling between transmit channels. We designed spoke pulses using magnitude least squares optimization with explicit constraint of SAR and power and compared the performance of the different pTx coils using the L-curve method.
Results
PTx arrays outperformed the conventional birdcage coil in all metrics except peak and average power efficiency. The presence of coupling exacerbated this power efficiency problem. At constant excitation fidelity, the pTx array with 24 channels arranged in three z-rows could decrease local SAR more than 4-fold (2-fold) for RF-shimming (2-spoke) compared to the birdcage coil for pulses of equal duration. Multi-row pTx coils had a marked performance advantage compared to single row designs, especially for coronal imaging.
Conclusion
PTx coils can simultaneously improve the excitation uniformity and reduce SAR compared to a birdcage coil when SAR metrics are explicitly constrained in the pulse design. |
| first_indexed | 2024-09-23T15:38:35Z |
| format | Article |
| id | mit-1721.1/110707 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T15:38:35Z |
| publishDate | 2017 |
| publisher | Wiley Blackwell |
| record_format | dspace |
| spelling | mit-1721.1/1107072022-10-02T03:06:19Z Comparison of simulated parallel transmit body arrays at 3 T using excitation uniformity, global SAR, local SAR, and power efficiency metrics Guérin, Bastien Gebhardt, Matthias Serano, Peter Adalsteinsson, Elfar Hamm, Michael Pfeuffer, Josef Nistler, Juergen Wald, Lawrence L. Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science Adalsteinsson, Elfar Purpose We compare the performance of eight parallel transmit (pTx) body arrays with up to 32 channels and a standard birdcage design. Excitation uniformity, local specific absorption rate (SAR), global SAR, and power metrics are analyzed in the torso at 3 T for radiofrequency (RF)-shimming and 2-spoke excitations. Methods We used a fast cosimulation strategy for field calculation in the presence of coupling between transmit channels. We designed spoke pulses using magnitude least squares optimization with explicit constraint of SAR and power and compared the performance of the different pTx coils using the L-curve method. Results PTx arrays outperformed the conventional birdcage coil in all metrics except peak and average power efficiency. The presence of coupling exacerbated this power efficiency problem. At constant excitation fidelity, the pTx array with 24 channels arranged in three z-rows could decrease local SAR more than 4-fold (2-fold) for RF-shimming (2-spoke) compared to the birdcage coil for pulses of equal duration. Multi-row pTx coils had a marked performance advantage compared to single row designs, especially for coronal imaging. Conclusion PTx coils can simultaneously improve the excitation uniformity and reduce SAR compared to a birdcage coil when SAR metrics are explicitly constrained in the pulse design. National Institutes of Health (U.S.) (R01EB0068547) National Institutes of Health (U.S.) (R01EB007942) National Institutes of Health (U.S.) (P41EB015896) 2017-07-14T18:50:02Z 2017-07-14T18:50:02Z 2015-02 2014-03 Article http://purl.org/eprint/type/JournalArticle 0740-3194 1522-2594 http://hdl.handle.net/1721.1/110707 Guérin, Bastien; Gebhardt, Matthias; Serano, Peter et al. “Comparison of Simulated Parallel Transmit Body Arrays at 3 T Using Excitation Uniformity, Global SAR, Local SAR, and Power Efficiency Metrics.” Magnetic Resonance in Medicine 73, 3 (April 2014): 1137–1150 © 2014 Wiley Periodicals, Inc. https://orcid.org/0000-0002-7637-2914 en_US http://dx.doi.org/10.1002/mrm.25243 Magnetic Resonance in Medicine Creative Commons Attribution-Noncommercial-Share Alike http://creativecommons.org/licenses/by-nc-sa/4.0/ application/pdf Wiley Blackwell PMC |
| spellingShingle | Guérin, Bastien Gebhardt, Matthias Serano, Peter Adalsteinsson, Elfar Hamm, Michael Pfeuffer, Josef Nistler, Juergen Wald, Lawrence L. Comparison of simulated parallel transmit body arrays at 3 T using excitation uniformity, global SAR, local SAR, and power efficiency metrics |
| title | Comparison of simulated parallel transmit body arrays at 3 T using excitation uniformity, global SAR, local SAR, and power efficiency metrics |
| title_full | Comparison of simulated parallel transmit body arrays at 3 T using excitation uniformity, global SAR, local SAR, and power efficiency metrics |
| title_fullStr | Comparison of simulated parallel transmit body arrays at 3 T using excitation uniformity, global SAR, local SAR, and power efficiency metrics |
| title_full_unstemmed | Comparison of simulated parallel transmit body arrays at 3 T using excitation uniformity, global SAR, local SAR, and power efficiency metrics |
| title_short | Comparison of simulated parallel transmit body arrays at 3 T using excitation uniformity, global SAR, local SAR, and power efficiency metrics |
| title_sort | comparison of simulated parallel transmit body arrays at 3 t using excitation uniformity global sar local sar and power efficiency metrics |
| url | http://hdl.handle.net/1721.1/110707 https://orcid.org/0000-0002-7637-2914 |
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