Local SAR, global SAR, transmitter power and excitation accuracy trade-offs in low flip-angle parallel transmit pulse design
Purpose We propose a constrained optimization approach for designing parallel transmit (pTx) pulses satisfying all regulatory and hardware limits. We study the trade-offs between excitation accuracy, local and global specific absorption rate (SAR), and maximum and average power for small flip-angle...
| Main Authors: | , , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
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Wiley Blackwell
2015
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| Online Access: | http://hdl.handle.net/1721.1/99687 |
| _version_ | 1826216930648784896 |
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| author | Guérin, Bastien Gebhardt, Matthias Cauley, Steven Adalsteinsson, Elfar 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 Cauley, Steven Adalsteinsson, Elfar Wald, Lawrence L. |
| author_sort | Guérin, Bastien |
| collection | MIT |
| description | Purpose
We propose a constrained optimization approach for designing parallel transmit (pTx) pulses satisfying all regulatory and hardware limits. We study the trade-offs between excitation accuracy, local and global specific absorption rate (SAR), and maximum and average power for small flip-angle pTx (eight channels) spokes pulses in the torso at 3 T and in the head at 7 T.
Methods
We compare the trade-offs between the above-mentioned quantities using the L-curve method. We use a primal-dual algorithm and a compressed set of local SAR matrices to design radio-frequency (RF) pulses satisfying all regulatory (including local SAR) and hardware constraints.
Results
Local SAR can be substantially reduced (factor of 2 or more) by explicitly constraining it in the pulse design process compared to constraining global SAR or pulse power alone. This often comes at the price of increased pulse power.
Conclusion
Simultaneous control of power and SAR is needed for the design of pTx pulses that are safe and can be played on the scanner. Constraining a single quantity can create large increase in the others, which can then rise above safety or hardware limits. Simultaneous constraint of local SAR and power is fast enough to be applicable in a clinical setting. |
| first_indexed | 2024-09-23T16:55:44Z |
| format | Article |
| id | mit-1721.1/99687 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T16:55:44Z |
| publishDate | 2015 |
| publisher | Wiley Blackwell |
| record_format | dspace |
| spelling | mit-1721.1/996872024-06-13T15:31:58Z Local SAR, global SAR, transmitter power and excitation accuracy trade-offs in low flip-angle parallel transmit pulse design Local specific absorption rate (SAR), global SAR, transmitter power, and excitation accuracy trade-offs in low flip-angle parallel transmit pulse design Guérin, Bastien Gebhardt, Matthias Cauley, Steven Adalsteinsson, Elfar Wald, Lawrence L. Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science Harvard University--MIT Division of Health Sciences and Technology Purpose We propose a constrained optimization approach for designing parallel transmit (pTx) pulses satisfying all regulatory and hardware limits. We study the trade-offs between excitation accuracy, local and global specific absorption rate (SAR), and maximum and average power for small flip-angle pTx (eight channels) spokes pulses in the torso at 3 T and in the head at 7 T. Methods We compare the trade-offs between the above-mentioned quantities using the L-curve method. We use a primal-dual algorithm and a compressed set of local SAR matrices to design radio-frequency (RF) pulses satisfying all regulatory (including local SAR) and hardware constraints. Results Local SAR can be substantially reduced (factor of 2 or more) by explicitly constraining it in the pulse design process compared to constraining global SAR or pulse power alone. This often comes at the price of increased pulse power. Conclusion Simultaneous control of power and SAR is needed for the design of pTx pulses that are safe and can be played on the scanner. Constraining a single quantity can create large increase in the others, which can then rise above safety or hardware limits. Simultaneous constraint of local SAR and power is fast enough to be applicable in a clinical setting. National Institutes of Health (U.S.) (Grant R01EB-0068547) National Institutes of Health (U.S.) (Grant R01EB-007942) National Institutes of Health (U.S.) (Grant P41EB-015896) Siemens-MIT Alliance 2015-11-03T18:13:02Z 2015-11-03T18:13:02Z 2013-06 2013-04 Article http://purl.org/eprint/type/JournalArticle 07403194 1522-2594 http://hdl.handle.net/1721.1/99687 Guérin, Bastien, Matthias Gebhardt, Steven Cauley, Elfar Adalsteinsson, and Lawrence L. Wald. “Local Specific Absorption Rate (SAR), Global SAR, Transmitter Power, and Excitation Accuracy Trade-Offs in Low Flip-Angle Parallel Transmit Pulse Design.” Magn. Reson. Med. 71, no. 4 (June 14, 2013): 1446–1457. en_US http://dx.doi.org/10.1002/mrm.24800 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 Cauley, Steven Adalsteinsson, Elfar Wald, Lawrence L. Local SAR, global SAR, transmitter power and excitation accuracy trade-offs in low flip-angle parallel transmit pulse design |
| title | Local SAR, global SAR, transmitter power and excitation accuracy trade-offs in low flip-angle parallel transmit pulse design |
| title_full | Local SAR, global SAR, transmitter power and excitation accuracy trade-offs in low flip-angle parallel transmit pulse design |
| title_fullStr | Local SAR, global SAR, transmitter power and excitation accuracy trade-offs in low flip-angle parallel transmit pulse design |
| title_full_unstemmed | Local SAR, global SAR, transmitter power and excitation accuracy trade-offs in low flip-angle parallel transmit pulse design |
| title_short | Local SAR, global SAR, transmitter power and excitation accuracy trade-offs in low flip-angle parallel transmit pulse design |
| title_sort | local sar global sar transmitter power and excitation accuracy trade offs in low flip angle parallel transmit pulse design |
| url | http://hdl.handle.net/1721.1/99687 |
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