Switching pTx: Time-Division Multiplexing for Improved kT Points Excitation with a Limited Number of RF Power Amplifiers

Motivation: Parallel transmission is a key technology to mitigate B1+ inhomogeneity and increased power deposition in ultra-high field MRI. Its performance is limited by the number of available Tx channels. Goal(s): Improving excitation homogeneity by time-division multiplexing of 16 Tx elements between 8 RF power amplifiers. Approach: An RF switch was built to alternately route 8 RFPAs to each row of a double-row 16-element coil array. The setup was tested for kT points excitation at 9.4T. Results: With the proposed time-division multiplexing, similar excitation fidelity as with 16 channels can be achieved with only 8 channels, but at the expense of increased SAR. Impact: Time-division multiplexing allows driving a larger number of Tx elements with a smaller number of RFPAs, resulting in improved pTx performance. This opens up new possibilities for using advanced multi-row pTx coils in sites with only 8 RFPAs available.