Investig Magn Reson Imaging.
2025 Sep;29(3):167-175. 10.13104/imri.2025.0030.
Sheath Current Effects in Dipole Antenna Arrays at 10.5 T: Influence of Cable Spacing and Trap Implementation
- Affiliations
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- 1Department of Biomedical Engineering, Hankuk University of Foreign Studies, Yongin, Korea
- 2Department of Elctronics Engineering, Hankuk University of Foreign Studies, Yongin, Korea
- KMID: 2572495
- DOI: http://doi.org/10.13104/imri.2025.0030
Abstract
- Purpose
This study aims to evaluate the impact of the sheath current from coaxial cables on the transmission magnetic (B1+) field efficiency of dipole antenna arrays for 10.5-tesla (T) magnetic resonance imaging (MRI).
Materials and Methods
Electromagnetic simulations and phantom experiments were conducted using 8- and 16-channel dipole antenna arrays. Each configuration varied in terms of the coaxial cable gap (2 cm and 7 cm) and the presence or absence of floating cable traps. All antennas were tuned to 447 MHz/10.5 T. The simulated and experimental B1+ field efficiencies (B1+ field normalized by the square root of the input power) of multiple arrays were obtained and compared using an actual flip-angle imaging sequence in a cylindrical phantom with tissue-equivalent properties.
Results
Simulated and experimental measurements of 8- and 16-channel dipole antenna arrays for ultra-high field (UHF) MRI showed excellent agreement, with less than ±10% deviation in B1+ efficiency. The highest efficiency (0.60 μT/√W) was achieved with 7 cm coaxial cable spacing. When the spacing was reduced to 2 cm, the B1+ efficiency decreased by up to 35%. Trap removal and suboptimal cable routing further degraded performance. Comparisons across the loop, dipole, and loop + dipole antenna arrays confirmed that the dipole antenna arrays are more sensitive to cable interference.
Conclusion
Coaxial cable spacing and trap existence play critical roles in determining the performance of dipole antenna arrays in UHF MRI. Effective cable management and optimized trap integration are essential for maintaining high B1+ efficiency in compact multichannel array designs. These findings highlight the importance of coaxial-cable management and trap design for achieving optimal transmission performance in practical MRI systems.
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