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Time‐Division Multiplexing for Parallel Transmission at Ultra‐High Field With Limited RF Channels.

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Title: Time‐Division Multiplexing for Parallel Transmission at Ultra‐High Field With Limited RF Channels.
Authors: Glang, Felix1,2 (AUTHOR) glang@tugraz.at, Solomakha, Georgiy A.1 (AUTHOR), Bosch, Dario1,3,4 (AUTHOR), Scheffler, Klaus1,3 (AUTHOR), Avdievich, Nikolai I.1 (AUTHOR)
Source: Magnetic Resonance in Medicine. May2026, Vol. 95 Issue 5, p2580-2593. 14p.
Subjects: Magnetic resonance imaging, Radio transmitters & transmission, Magnetic resonance, Antenna arrays, Time division multiple access, Electronic pulse techniques
Abstract: Purpose: Investigating time‐division multiplexing for parallel transmission in ultra high‐field imaging, striving for homogeneous whole brain excitation with a limited number of RF channels. Methods: A fast RF switch was built to alternately route 8 transmit channels to each row of a double‐row 16‐element transmit coil array at a 9.4 T human MRI system. Methods for SAR monitoring and pulse design for this temporal degree of freedom were developed and investigated in electromagnetic simulations and in vivo measurements, employing parallel transmission kT points pulses aiming for homogeneous whole‐brain excitation. The achievable trade‐off between local SAR and excitation homogeneity was compared for multiplexed and simultaneous transmission. Results: Using time‐division multiplexing, similar excitation fidelity as with 16 transmit channels can be achieved with only 8 channels. For instance, multiplexing reduces the flip angle inhomogeneity by 2.22‐fold compared to exciting only a single row of the array, and by 1.85‐fold compared to statically splitting and routing 8 channels to 16 transmit coil elements. As a trade‐off, compared to simultaneous excitation, multiplexing requires either increased pulse duration or amplitudes, the latter causing increased SAR. However, with appropriate SAR‐aware pulse design, the multiplexing‐induced local SAR increase can be controlled. This allows for viable pulse design solutions for the considered low‐flip‐angle imaging scenarios. Conclusion: Time‐division multiplexing allows driving a larger number of transmit elements with a smaller number of RF channels, resulting in improved parallel transmission performance. This opens up new possibilities for using advanced multi‐row transmit coil arrays in sites with only 8 RF channels available. [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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DbLabel: Engineering Source
An: 192088846
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  Data: Time‐Division Multiplexing for Parallel Transmission at Ultra‐High Field With Limited RF Channels.
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  Data: <searchLink fieldCode="JN" term="%22Magnetic+Resonance+in+Medicine%22">Magnetic Resonance in Medicine</searchLink>. May2026, Vol. 95 Issue 5, p2580-2593. 14p.
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  Data: <searchLink fieldCode="DE" term="%22Magnetic+resonance+imaging%22">Magnetic resonance imaging</searchLink><br /><searchLink fieldCode="DE" term="%22Radio+transmitters+%26+transmission%22">Radio transmitters & transmission</searchLink><br /><searchLink fieldCode="DE" term="%22Magnetic+resonance%22">Magnetic resonance</searchLink><br /><searchLink fieldCode="DE" term="%22Antenna+arrays%22">Antenna arrays</searchLink><br /><searchLink fieldCode="DE" term="%22Time+division+multiple+access%22">Time division multiple access</searchLink><br /><searchLink fieldCode="DE" term="%22Electronic+pulse+techniques%22">Electronic pulse techniques</searchLink>
– Name: Abstract
  Label: Abstract
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  Data: Purpose: Investigating time‐division multiplexing for parallel transmission in ultra high‐field imaging, striving for homogeneous whole brain excitation with a limited number of RF channels. Methods: A fast RF switch was built to alternately route 8 transmit channels to each row of a double‐row 16‐element transmit coil array at a 9.4 T human MRI system. Methods for SAR monitoring and pulse design for this temporal degree of freedom were developed and investigated in electromagnetic simulations and in vivo measurements, employing parallel transmission kT points pulses aiming for homogeneous whole‐brain excitation. The achievable trade‐off between local SAR and excitation homogeneity was compared for multiplexed and simultaneous transmission. Results: Using time‐division multiplexing, similar excitation fidelity as with 16 transmit channels can be achieved with only 8 channels. For instance, multiplexing reduces the flip angle inhomogeneity by 2.22‐fold compared to exciting only a single row of the array, and by 1.85‐fold compared to statically splitting and routing 8 channels to 16 transmit coil elements. As a trade‐off, compared to simultaneous excitation, multiplexing requires either increased pulse duration or amplitudes, the latter causing increased SAR. However, with appropriate SAR‐aware pulse design, the multiplexing‐induced local SAR increase can be controlled. This allows for viable pulse design solutions for the considered low‐flip‐angle imaging scenarios. Conclusion: Time‐division multiplexing allows driving a larger number of transmit elements with a smaller number of RF channels, resulting in improved parallel transmission performance. This opens up new possibilities for using advanced multi‐row transmit coil arrays in sites with only 8 RF channels available. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
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  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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        Value: 10.1002/mrm.70230
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        Text: English
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      – SubjectFull: Magnetic resonance
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      – SubjectFull: Antenna arrays
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      – SubjectFull: Time division multiple access
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      – SubjectFull: Electronic pulse techniques
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      – TitleFull: Time‐Division Multiplexing for Parallel Transmission at Ultra‐High Field With Limited RF Channels.
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            NameFull: Glang, Felix
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            NameFull: Solomakha, Georgiy A.
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              M: 05
              Text: May2026
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              Y: 2026
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              Value: 95
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