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