Improved Decoupling for Low Frequency MRI Arrays using Non-conventional Preamplifier Impedance

Juan Diego Sanchez, Daniel Højrup Johansen, Rie Beck Hansen, Esben S. Szocska Hansen, Christoffer Laustsen, Vitaliy Zhurbenko, Jan Henrik Ardenkjær-Larsen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Objective: In this study, we describe a method to improve preamplifier decoupling in low frequency MRI receive coil arrays, where sample loading is low and coils exhibit a high Q-factor. Methods: The method relies on the higher decoupling obtained when coils are matched to an impedance higher than 50 Ω. Preamplifiers with inductive (and low resistive) input impedance, increase even further the effectiveness of the method. Results: We show that for poorly sample loaded coils, coupling to other elements in an array is a major source of SNR degradation due to a reduction of the coil Q-factor. An 8-channel 13C array at 32 MHz for imaging of the human head has been designed following this strategy. The improved decoupling even allowed constructing the array without overlapping of neighboring coils. Parallel imaging performance is also evaluated demonstrating a better spatial encoding of the array due to its non-overlapped geometry. Conclusion: The proposed design strategy for coil arrays is beneficial for low frequency coils where the coil thermal noise is dominant. The method has been demonstrated on an 8-channel array for the human head for 13C MRI at 3 T (32 MHz), with almost 2-fold SNR enhancement when compared to a traditional array of similar size and number of elements. Significance: The proposed method is of relevance for low frequency arrays, where sample loading is low, and noise correlation is high due to insufficient coil decoupling.
Original languageEnglish
JournalI E E E Transactions on Biomedical Engineering
Volume66
Issue number7
Pages (from-to)1940 - 1948
ISSN0018-9294
DOIs
Publication statusPublished - 2019

Keywords

  • RF coil
  • SNR
  • 13C MRI
  • Hyperpolarization

Cite this

@article{162852c9e0014d6890fd42e51aef9925,
title = "Improved Decoupling for Low Frequency MRI Arrays using Non-conventional Preamplifier Impedance",
abstract = "Objective: In this study, we describe a method to improve preamplifier decoupling in low frequency MRI receive coil arrays, where sample loading is low and coils exhibit a high Q-factor. Methods: The method relies on the higher decoupling obtained when coils are matched to an impedance higher than 50 Ω. Preamplifiers with inductive (and low resistive) input impedance, increase even further the effectiveness of the method. Results: We show that for poorly sample loaded coils, coupling to other elements in an array is a major source of SNR degradation due to a reduction of the coil Q-factor. An 8-channel 13C array at 32 MHz for imaging of the human head has been designed following this strategy. The improved decoupling even allowed constructing the array without overlapping of neighboring coils. Parallel imaging performance is also evaluated demonstrating a better spatial encoding of the array due to its non-overlapped geometry. Conclusion: The proposed design strategy for coil arrays is beneficial for low frequency coils where the coil thermal noise is dominant. The method has been demonstrated on an 8-channel array for the human head for 13C MRI at 3 T (32 MHz), with almost 2-fold SNR enhancement when compared to a traditional array of similar size and number of elements. Significance: The proposed method is of relevance for low frequency arrays, where sample loading is low, and noise correlation is high due to insufficient coil decoupling.",
keywords = "RF coil, SNR, 13C MRI, Hyperpolarization",
author = "Sanchez, {Juan Diego} and Johansen, {Daniel H{\o}jrup} and Hansen, {Rie Beck} and Hansen, {Esben S. Szocska} and Christoffer Laustsen and Vitaliy Zhurbenko and Ardenkj{\ae}r-Larsen, {Jan Henrik}",
year = "2019",
doi = "10.1109/TBME.2018.2881203",
language = "English",
volume = "66",
pages = "1940 -- 1948",
journal = "I E E E Transactions on Biomedical Engineering",
issn = "0018-9294",
publisher = "Institute of Electrical and Electronics Engineers",
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}

Improved Decoupling for Low Frequency MRI Arrays using Non-conventional Preamplifier Impedance. / Sanchez, Juan Diego; Johansen, Daniel Højrup; Hansen, Rie Beck; Hansen, Esben S. Szocska; Laustsen, Christoffer; Zhurbenko, Vitaliy; Ardenkjær-Larsen, Jan Henrik.

In: I E E E Transactions on Biomedical Engineering, Vol. 66, No. 7, 2019, p. 1940 - 1948.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Improved Decoupling for Low Frequency MRI Arrays using Non-conventional Preamplifier Impedance

AU - Sanchez, Juan Diego

AU - Johansen, Daniel Højrup

AU - Hansen, Rie Beck

AU - Hansen, Esben S. Szocska

AU - Laustsen, Christoffer

AU - Zhurbenko, Vitaliy

AU - Ardenkjær-Larsen, Jan Henrik

PY - 2019

Y1 - 2019

N2 - Objective: In this study, we describe a method to improve preamplifier decoupling in low frequency MRI receive coil arrays, where sample loading is low and coils exhibit a high Q-factor. Methods: The method relies on the higher decoupling obtained when coils are matched to an impedance higher than 50 Ω. Preamplifiers with inductive (and low resistive) input impedance, increase even further the effectiveness of the method. Results: We show that for poorly sample loaded coils, coupling to other elements in an array is a major source of SNR degradation due to a reduction of the coil Q-factor. An 8-channel 13C array at 32 MHz for imaging of the human head has been designed following this strategy. The improved decoupling even allowed constructing the array without overlapping of neighboring coils. Parallel imaging performance is also evaluated demonstrating a better spatial encoding of the array due to its non-overlapped geometry. Conclusion: The proposed design strategy for coil arrays is beneficial for low frequency coils where the coil thermal noise is dominant. The method has been demonstrated on an 8-channel array for the human head for 13C MRI at 3 T (32 MHz), with almost 2-fold SNR enhancement when compared to a traditional array of similar size and number of elements. Significance: The proposed method is of relevance for low frequency arrays, where sample loading is low, and noise correlation is high due to insufficient coil decoupling.

AB - Objective: In this study, we describe a method to improve preamplifier decoupling in low frequency MRI receive coil arrays, where sample loading is low and coils exhibit a high Q-factor. Methods: The method relies on the higher decoupling obtained when coils are matched to an impedance higher than 50 Ω. Preamplifiers with inductive (and low resistive) input impedance, increase even further the effectiveness of the method. Results: We show that for poorly sample loaded coils, coupling to other elements in an array is a major source of SNR degradation due to a reduction of the coil Q-factor. An 8-channel 13C array at 32 MHz for imaging of the human head has been designed following this strategy. The improved decoupling even allowed constructing the array without overlapping of neighboring coils. Parallel imaging performance is also evaluated demonstrating a better spatial encoding of the array due to its non-overlapped geometry. Conclusion: The proposed design strategy for coil arrays is beneficial for low frequency coils where the coil thermal noise is dominant. The method has been demonstrated on an 8-channel array for the human head for 13C MRI at 3 T (32 MHz), with almost 2-fold SNR enhancement when compared to a traditional array of similar size and number of elements. Significance: The proposed method is of relevance for low frequency arrays, where sample loading is low, and noise correlation is high due to insufficient coil decoupling.

KW - RF coil

KW - SNR

KW - 13C MRI

KW - Hyperpolarization

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DO - 10.1109/TBME.2018.2881203

M3 - Journal article

C2 - 30442598

VL - 66

SP - 1940

EP - 1948

JO - I E E E Transactions on Biomedical Engineering

JF - I E E E Transactions on Biomedical Engineering

SN - 0018-9294

IS - 7

ER -