Investig Magn Reson Imaging.  2024 Sep;28(3):132-139. 10.13104/imri.2024.0016.

Dipole Element Evaluation of 8-Channel Arrays for Human Head Imaging at 10.5 Tesla MRI

• Woo MK

• KMID: 2559681
• DOI: http://doi.org/10.13104/imri.2024.0016

Abstract

Purpose
To optimize B₁⁺ (transmit magnetic field generated by radiofrequency coils) and specific absorption ratio (SAR) efficiency for human head imaging at 10.5 tesla (T) with various 8-channel dipole antenna element arrays.
Materials and Methods
Electromagnetic simulations were employed to model threedimensional arrays including 8-channel half-wave, fractionated, meander-ends, and inductor-shortened dipole antennas. The B₁⁺ efficiency and SAR efficiency were evaluated using a cylindrical phantom and a human model for human head imaging. The B₁⁺ efficiency, peak 10 g SAR, and SAR efficiency values of different dipole antenna arrays, including inductorshortened dipole arrays with coaxial cables additionally, were summarized and compared for practical applications.
Results
The inductor-shortened dipole antenna array demonstrated the highest SAR efficiency values among the arrays with cylindrical phantoms. In the human model, the fractionated dipole showed the highest B₁⁺ efficiency values, whereas the inductor- shortened dipole antenna array exhibited superior SAR efficiency compared to the other dipole antenna arrays. Further, simulation data with and without coaxial cables indicated that the inductor-shortened dipole antenna array without cables exhibited a 9.2% higher B₁⁺ efficiency and 14.6% lower peak 10 g SAR than the array with cables. Consequently, the SAR efficiency of the inductor-shortened dipole antenna array without coaxial cables was 14.9% higher than that with coaxial cables.
Conclusion
The inductor-shortened dipole antenna array demonstrated higher SAR efficiency with low SAR values for human brain imaging at 10.5 T. Consequently, the optimization of the coaxial cable setup further enhanced its suitability for ultra-high field applications.

Keyword

Magnetic resonance imaging; Neuroimaging