Effect of radiofrequency shield diameter on signal‐to‐noise ratio at ultra‐high field MRI
- 19 January 2021
- journal article
- research article
- Published by Wiley in Magnetic Resonance in Medicine
- Vol. 85 (6), 3522-3530
- https://doi.org/10.1002/mrm.28670
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.Funding Information
- National Science Foundation (1453675)
- Cancer Prevention and Research Institute of Texas (RR180056)
- National Institutes of Health (U01 EB025144, R01 EB024536, R01 EB021277, P41 E)
This publication has 30 references indexed in Scilit:
- Optimum coupling and multimode excitation of traveling-waves in a whole-body 9.4T scannerMagnetic Resonance in Medicine, 2012
- Whole body traveling wave magnetic resonance imaging at high field strength: Homogeneity, efficiency, and energy deposition as compared with traditional excitation mechanismsMagnetic Resonance in Medicine, 2011
- Design of a radiative surface coil array element at 7 T: The single‐side adapted dipole antennaMagnetic Resonance in Medicine, 2011
- A 32‐channel lattice transmission line array for parallel transmit and receive MRI at 7 teslaMagnetic Resonance in Medicine, 2010
- MRI and localized proton spectroscopy in human leg muscle at 7 tesla using longitudinal traveling wavesMagnetic Resonance in Medicine, 2010
- The Virtual Family—development of surface-based anatomical models of two adults and two children for dosimetric simulationsPhysics in Medicine & Biology, 2009
- Performance evaluation of a 32‐element head array with respect to the ultimate intrinsic SNRNMR in Biomedicine, 2009
- Travelling-wave nuclear magnetic resonanceNature, 2009
- 32‐channel 3 Tesla receive‐only phased‐array head coil with soccer‐ball element geometryMagnetic Resonance in Medicine, 2006
- Radiofrequency shielding of surface coils at 4.0 tJournal of Magnetic Resonance Imaging, 1995