Effect of radiofrequency shield diameter on signal-to-noise ratio at ultra-high field MRI

Bei Zhang, Gregor Adriany, Lance Delabarre, Jerahmie Radder, Russell Lagore, Brian Rutt, Qing X. Yang, Kamil Ugurbil, Riccardo Lattanzi

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose: In this work, we investigated how the position of the radiofrequency (RF) shield can affect the signal-to-noise ratio (SNR) of a receive RF coil. Our aim was to obtain physical insight for the design of a 10.5T 32-channel head coil, subject to the constraints on the diameter of the RF shield imposed by the head gradient coil geometry. Method: We used full-wave numerical simulations to investigate how the SNR of an RF receive coil depends on the diameter of the RF shield at ultra-high magnetic field (UHF) strengths (≥7T). Results: Our simulations showed that there is an SNR-optimal RF shield size at UHF strength, whereas at low field the SNR monotonically increases with the shield diameter. For a 32-channel head coil at 10.5T, an optimally sized RF shield could act as a cylindrical waveguide and increase the SNR in the brain by 27% compared to moving the shield as far as possible from the coil. Our results also showed that a separate transmit array between the RF shield and the receive array could considerably reduce SNR even if they are decoupled. Conclusion: At sufficiently high magnetic field strength, the design of local RF coils should be optimized together with the design of the RF shield to benefit from both near field and resonant modes.

Original languageEnglish (US)
Pages (from-to)3522-3530
Number of pages9
JournalMagnetic resonance in medicine
Volume85
Issue number6
DOIs
StateAccepted/In press - 2021

Bibliographical note

Funding Information:
The authors thank Dr. Anke Henning and Dr. Nikolai Avdievich for useful discussions about shielding effects on receive coils. This work was supported in part by NIH U01 EB025144, NIH R01 EB024536, NIH S10 RR029672, NSF 1453675 and Cancer Prevention and Research Institute of Texas RR180056, and was performed under the rubric of the Center for Advanced Imaging Innovation and Research (CAI2R, www.cai2r.net ) and CMRR, National Centers for Biomedical Imaging and Bioengineering (NIH P41 EB017183 and P41 EB015894).

Funding Information:
National Institutes of Health, Grant/Award Numbers: U01 EB025144, R01 EB024536, R01 EB021277 and P41 EB017183; National Science Foundation (NSF), Grant/Award Number: 1453675; Cancer Prevention and Research Institute of Texas, Grant Number: RR180056 The authors thank Dr. Anke Henning and Dr. Nikolai Avdievich for useful discussions about shielding effects on receive coils. This work was supported in part by NIH U01 EB025144, NIH R01 EB024536, NIH S10 RR029672, NSF 1453675 and Cancer Prevention and Research Institute of Texas RR180056, and was performed under the rubric of the Center for Advanced Imaging Innovation and Research (CAI2R, www.cai2r.net) and CMRR, National Centers for Biomedical Imaging and Bioengineering (NIH P41 EB017183 and P41 EB015894).

Publisher Copyright:
© 2021 International Society for Magnetic Resonance in Medicine

Keywords

  • RF coil
  • RF shield
  • signal to noise ratio
  • ultra-high field MRI

PubMed: MeSH publication types

  • Journal Article

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