RF transmit performance comparison for several MRI head array geometries

We numerically investigated several magnetic resonance imaging radiofrequency transmit coil arrays with different array diameters and tuning conditions. Compared with a dual-row array of 230 mm in diameter, it is difficult to achieve high transmit performance when the diameter is increased to 280 mm, while maintaining high load independence and a predictable distribution of current through each element. All arrays investigated provided similar inhomogeneity when each array row was accurately excited in a circular polarization mode, and the phase shift between rows and asymmetry in the excitation power for each row were properly adjusted.