TY - JOUR
T1 - Manipulating transmit and receive sensitivities of radiofrequency surface coils using shielded and unshielded high-permittivity materials
AU - Vaidya, Manushka V.
AU - Deniz, Cem M.
AU - Collins, Christopher M.
AU - Sodickson, Daniel K.
AU - Lattanzi, Riccardo
N1 - Funding Information:
Acknowledgements This work was supported in part by grants NIH R01 EB021277, NIH R01 EB002568, NIH R01 EB011551, NIH R01 EB024536, and NSF 1453675, and was performed under the rubric of the Center for Advanced Imaging Innovation and Research (http:// www.cai2r.net/), a National Institute of Biomedical Imaging and Bioengineering Biomedical Technology Resource Center (NIH P41 EB017183). The authors thank Sebastian Rupprecht for discussions regarding achievable conductivities in ceramic high-permittivity materials.
Funding Information:
This work was supported in part by grants NIH R01 EB021277, NIH R01 EB002568, NIH R01 EB011551, NIH R01 EB024536, and NSF 1453675, and was performed under the rubric of the Center for Advanced Imaging Innovation and Research (http://www.cai2r.net/), a National Institute of Biomedical Imaging and Bioengineering Biomedical Technology Resource Center (NIH P41 EB017183). The authors thank Sebastian Rupprecht for discussions regarding achievable conductivities in ceramic high-permittivity materials.
Publisher Copyright:
© 2017, ESMRMB.
PY - 2018/6/1
Y1 - 2018/6/1
N2 - Objective: To use high-permittivity materials (HPM) positioned near radiofrequency (RF) surface coils to manipulate transmit/receive field patterns. Materials and methods: A large HPM pad was placed below the RF coil to extend the field of view (FOV). The resulting signal-to-noise ratio (SNR) was compared with that of other coil configurations covering the same FOV in simulations and experiments at 7 T. Transmit/receive efficiency was evaluated when HPM discs with or without a partial shield were positioned at a distance from the coil. Finally, we evaluated the increase in transmit homogeneity for a four-channel array with HPM discs interposed between adjacent coil elements. Results: Various configurations of HPM increased SNR, transmit/receive efficiency, excitation/reception sensitivity overlap, and FOV when positioned near a surface coil. For a four-channel array driven in quadrature, shielded HPM discs enhanced the field below the discs as well as at the center of the sample as compared with other configurations with or without unshielded HPM discs. Conclusion: Strategically positioning HPM at a distance from a surface coil or array can increase the overlap between excitation/reception sensitivities, and extend the FOV of a single coil for reduction of the number of channels in an array while minimally affecting the SNR.
AB - Objective: To use high-permittivity materials (HPM) positioned near radiofrequency (RF) surface coils to manipulate transmit/receive field patterns. Materials and methods: A large HPM pad was placed below the RF coil to extend the field of view (FOV). The resulting signal-to-noise ratio (SNR) was compared with that of other coil configurations covering the same FOV in simulations and experiments at 7 T. Transmit/receive efficiency was evaluated when HPM discs with or without a partial shield were positioned at a distance from the coil. Finally, we evaluated the increase in transmit homogeneity for a four-channel array with HPM discs interposed between adjacent coil elements. Results: Various configurations of HPM increased SNR, transmit/receive efficiency, excitation/reception sensitivity overlap, and FOV when positioned near a surface coil. For a four-channel array driven in quadrature, shielded HPM discs enhanced the field below the discs as well as at the center of the sample as compared with other configurations with or without unshielded HPM discs. Conclusion: Strategically positioning HPM at a distance from a surface coil or array can increase the overlap between excitation/reception sensitivities, and extend the FOV of a single coil for reduction of the number of channels in an array while minimally affecting the SNR.
KW - Computer Simulation
KW - Electromagnetic Fields
KW - Magnetic Resonance Imaging
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U2 - 10.1007/s10334-017-0657-5
DO - 10.1007/s10334-017-0657-5
M3 - Article
C2 - 29110240
AN - SCOPUS:85033432450
VL - 31
SP - 355
EP - 366
JO - Magnetic Resonance Materials in Physics, Biology, and Medicine
JF - Magnetic Resonance Materials in Physics, Biology, and Medicine
SN - 0968-5243
IS - 3
ER -