Abstract
INTRODUCTION: Various research sites are pursuing 14 T MRI systems. However, both local SAR and RF transmit field inhomogeneity will increase. The aim of this simulation study is to investigate the trade-offs between peak local SAR and flip angle uniformity for five transmit coil array designs at 14 T in comparison to 7 T.
METHODS: Investigated coil array designs are: 8 dipole antennas (8D), 16 dipole antennas (16D), 8 loop coils (8D), 16 loop coils (16L), 8 dipoles/8 loop coils (8D8L) and for reference 8 dipoles at 7 T. Both RF shimming and k T-points were investigated by plotting L-curves of peak SAR levels vs flip angle homogeneity.
RESULTS: For RF shimming, the 16L array performs best. For k T-points, superior flip angle homogeneity is achieved at the expense of more power deposition, and the dipole arrays outperform the loop coil arrays.
DISCUSSION AND CONCLUSION: For most arrays and regular imaging, the constraint on head SAR is reached before constraints on peak local SAR are violated. Furthermore, the different drive vectors in k T-points alleviate strong peaks in local SAR. Flip angle inhomogeneity can be alleviated by k T-points at the expense of larger power deposition. For k T-points, the dipole arrays seem to outperform loop coil arrays.
Original language | English |
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Pages (from-to) | 245-255 |
Number of pages | 11 |
Journal | Magma - Magnetic Resonance Materials In Physics Biology And Medicine |
Volume | 36 |
Issue number | 2 |
DOIs | |
Publication status | Published - Apr 2023 |
Keywords
- Computer Simulation
- Magnetic Resonance Imaging/methods
- Phantoms, Imaging
- Radio Waves
- 14T
- Simulation study
- Flip angle homogeneity
- SAR assesment
- Coil designs