Local SAR in parallel transmission pulse design
The management of local and global power deposition in human subjects (specific absorption rate, SAR) is a fundamental constraint to the application of parallel transmission (pTx) systems. Even though the pTx and single channel have to meet the same SAR requirements, the complex behavior of the spat...
| Main Authors: | , , , |
|---|---|
| Other Authors: | |
| Format: | Article |
| Language: | en_US |
| Published: |
Wiley Blackwell
2014
|
| Online Access: | http://hdl.handle.net/1721.1/85878 https://orcid.org/0000-0002-7637-2914 |
| _version_ | 1811070603567824896 |
|---|---|
| author | Lee, Joonsung Gebhardt, Matthias Adalsteinsson, Elfar Wald, Lawrence |
| author2 | Harvard University--MIT Division of Health Sciences and Technology |
| author_facet | Harvard University--MIT Division of Health Sciences and Technology Lee, Joonsung Gebhardt, Matthias Adalsteinsson, Elfar Wald, Lawrence |
| author_sort | Lee, Joonsung |
| collection | MIT |
| description | The management of local and global power deposition in human subjects (specific absorption rate, SAR) is a fundamental constraint to the application of parallel transmission (pTx) systems. Even though the pTx and single channel have to meet the same SAR requirements, the complex behavior of the spatial distribution of local SAR for transmission arrays poses problems that are not encountered in conventional single-channel systems and places additional requirements on pTx radio frequency pulse design. We propose a pTx pulse design method which builds on recent work to capture the spatial distribution of local SAR in numerical tissue models in a compressed parameterization in order to incorporate local SAR constraints within computation times that accommodate pTx pulse design during an in vivo magnetic resonance imaging scan. Additionally, the algorithm yields a protocol-specific ultimate peak in local SAR, which is shown to bound the achievable peak local SAR for a given excitation profile fidelity. The performance of the approach was demonstrated using a numerical human head model and a 7 Tesla eight-channel transmit array. The method reduced peak local 10 g SAR by 14–66% for slice-selective pTx excitations and 2D selective pTx excitations compared to a pTx pulse design constrained only by global SAR. The primary tradeoff incurred for reducing peak local SAR was an increase in global SAR, up to 34% for the evaluated examples, which is favorable in cases where local SAR constraints dominate the pulse applications. |
| first_indexed | 2024-09-23T08:38:40Z |
| format | Article |
| id | mit-1721.1/85878 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T08:38:40Z |
| publishDate | 2014 |
| publisher | Wiley Blackwell |
| record_format | dspace |
| spelling | mit-1721.1/858782022-09-30T10:11:32Z Local SAR in parallel transmission pulse design Lee, Joonsung Gebhardt, Matthias Adalsteinsson, Elfar Wald, Lawrence Harvard University--MIT Division of Health Sciences and Technology Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science Lee, Joonsung Wald, Lawrence Adalsteinsson, Elfar The management of local and global power deposition in human subjects (specific absorption rate, SAR) is a fundamental constraint to the application of parallel transmission (pTx) systems. Even though the pTx and single channel have to meet the same SAR requirements, the complex behavior of the spatial distribution of local SAR for transmission arrays poses problems that are not encountered in conventional single-channel systems and places additional requirements on pTx radio frequency pulse design. We propose a pTx pulse design method which builds on recent work to capture the spatial distribution of local SAR in numerical tissue models in a compressed parameterization in order to incorporate local SAR constraints within computation times that accommodate pTx pulse design during an in vivo magnetic resonance imaging scan. Additionally, the algorithm yields a protocol-specific ultimate peak in local SAR, which is shown to bound the achievable peak local SAR for a given excitation profile fidelity. The performance of the approach was demonstrated using a numerical human head model and a 7 Tesla eight-channel transmit array. The method reduced peak local 10 g SAR by 14–66% for slice-selective pTx excitations and 2D selective pTx excitations compared to a pTx pulse design constrained only by global SAR. The primary tradeoff incurred for reducing peak local SAR was an increase in global SAR, up to 34% for the evaluated examples, which is favorable in cases where local SAR constraints dominate the pulse applications. Siemens Corporation National Institutes of Health (U.S.) (Grant NIH R01EB006847) National Institutes of Health (U.S.) (Grant NIH R01EB007942) National Center for Research Resources (U.S.) (Grant P41RR14075) Siemens-MIT Alliance 2014-03-21T16:33:43Z 2014-03-21T16:33:43Z 2011-11 2011-06 Article http://purl.org/eprint/type/JournalArticle 07403194 1522-2594 http://hdl.handle.net/1721.1/85878 Lee, Joonsung, Matthias Gebhardt, Lawrence L. Wald, and Elfar Adalsteinsson. “Local SAR in Parallel Transmission Pulse Design.” Magnetic Resonance Medicine 67, no. 6 (June 2012): 1566–1578. https://orcid.org/0000-0002-7637-2914 en_US http://dx.doi.org/10.1002/mrm.23140 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 | Lee, Joonsung Gebhardt, Matthias Adalsteinsson, Elfar Wald, Lawrence Local SAR in parallel transmission pulse design |
| title | Local SAR in parallel transmission pulse design |
| title_full | Local SAR in parallel transmission pulse design |
| title_fullStr | Local SAR in parallel transmission pulse design |
| title_full_unstemmed | Local SAR in parallel transmission pulse design |
| title_short | Local SAR in parallel transmission pulse design |
| title_sort | local sar in parallel transmission pulse design |
| url | http://hdl.handle.net/1721.1/85878 https://orcid.org/0000-0002-7637-2914 |
| work_keys_str_mv | AT leejoonsung localsarinparalleltransmissionpulsedesign AT gebhardtmatthias localsarinparalleltransmissionpulsedesign AT adalsteinssonelfar localsarinparalleltransmissionpulsedesign AT waldlawrence localsarinparalleltransmissionpulsedesign |