First experimental results using RF Elements with Switching Transmit Sensitivities at ultrahigh field MRI

Motivation: Dipole RF elements with electronically switchable B1 field patterns have been shown to improve receive performance. The question whether they are beneficial for transmission is still open. Goal(s): Improve flip angle homogeneity by modulating the Tx sensitivity of a dipole during excitation. Approach: An RF coil built from eight dipoles with electronically switchable sensitivities was constructed. Achievable flip angle homogeneity with 2-kT-points pulses was evaluated in simulations and in experiments. Results: Flip angle homogeneity could be increased by electronically switching the Tx sensitivity during the course of the RF pulse. Impact: RF elements with switchable transmit sensitivities offer a novel degree of freedom for excitation that promises improved flip angle homogeneity. This addresses one of the most pressing problems in ultra-high field MRI.