Purpose: The SNR at the center of a spherical phantom of known electrical properties was measured in quasi-identical experimental conditions as a function of magnetic field strength between 3 T and 11.7 T. Methods: The SNR was measured at the center of a spherical water saline phantom with a gradient-recalled echo sequence. Measurements were performed at NeuroSpin at 3, 7, and 11.7 T. The phantom was then shipped to Maastricht University and then to the University of Minnesota for additional data points at 7, 9.4, and 10.5 T. Experiments were carried out with the exact same type of birdcage volume coil (except at 3 T, where a similar coil was used) to attempt at isolating the evolution of SNR with field strength alone. Phantom electrical properties were characterized over the corresponding frequency range. Results: Electrical properties were found to barely vary over the frequency range. Removing the influence of the flip-angle excitation inhomogeneity was crucial, as expected. After such correction, measurements revealed a gain of SNR growing as B01.94 ± 0.16 compared with B02.13 according to ultimate intrinsic SNR theory. Conclusions: By using quasi-identical experimental setups (RF volume coil, phantom, electrical properties, and protocol), this work reports experimental data between 3 T and 11.7 T, enabling the comparison with SNR theories in which conductivity and permittivity can be assumed to be constant with respect to field strength. According to ultimate SNR theory, these results can be reasonably extrapolated to the performance of receive arrays with greater than about 32 elements for central SNR in the same spherical phantom.
Bibliographical noteFunding Information:
information Agence Nationale de la Recherche (ANR), Grant/Award Number: ANR-21-ESRE-0006; European Union H2020, Grant/Award Number: AROMA-885876; National Institutes of Health (NIH), USA, Grant/Award Numbers: P41 EB027061, U01 EB025144; National Institutes of Health; Agence Nationale de la Recherche; Horizon 2020; European UnionThe authors thank the IRFU team at CEA for the design and commissioning of the 11.7T magnet. The authors also wish to thank David Hoult, Klaas Pruessmann, and Riccardo Lattanzi for the valuable discussions.
European Union Horizon 2020 Research and Innovation program (885876; AROMA); a French government grant managed by the Agence Nationale de la Recherche under the program “Investissements d'avenir” (ANR‐21‐ESRE‐0006); and the National Institutes of Health (U01 EB025144 and P41 EB027061)
© 2022 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.
- field strength
- signal-to-noise ratio
- volume coil
Center for Magnetic Resonance Research (CMRR) tags
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't
- Research Support, N.I.H., Extramural