For ultra-high field and frequency (UHF) magnetic resonance imaging (MRI), the associated short wavelengths in biological tissues leads to penetration and homogeneity issues at 10.5 tesla (T) and require antenna transmit arrays for efficiently generated 447 MHz B1+ fields (defined as the transmit radiofrequency (RF) magnetic field generated by RF coils). Previously, we evaluated a 16-channel combined loop + dipole antenna (LD) 10.5 T head array. While the LD array configuration did not achieve the desired B1+ efficiency, it showed an improvement of the specific absorption rate (SAR) efficiency compared to the separate 8-channel loop and separate 8-channel dipole antenna arrays at 10.5 T. Here we compare a 16-channel dipole antenna array with a 16-channel LD array of the same dimensions to evaluate B1+ efficiency, 10 g SAR, and SAR efficiency. The 16-channel dipole antenna array achieved a 24% increase in B1+ efficiency in the electromagnetic simulation and MR experiment compared to the LD array, as measured in the central region of a phantom. Based on the simulation results with a human model, we estimate that a 16-channel dipole antenna array for human brain imaging can increase B1+ efficiency by 15% with similar SAR efficiency compared to a 16-channel LD head array.
|Original language||English (US)|
|State||Published - Nov 1 2021|
Bibliographical noteFunding Information:
Funding: This research was funded by the U.S. Department of National Institutes of Health under Grants U01-EB025144, S10-RR029672, P41-EB015894, P41-EB027061, P30-NS076408, National Research Foundation of Korea (NRF-2021R1A2B5B03002783) and the BK21 FOUR program of the Education and Research Program for Future ICT Pioneers, Seoul National University in A0426-20210100.
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.
- Antenna coupling
- Dipole antenna array
- Human head imaging
- Loop + dipole antenna
- Magnetic resonance imaging
- Multi-channel arrays
- Ultra-high field