Robust Parallel Excitation Pulse Design

Introduction Parallel excitation employs multiple transmit channels and coils, each driven by independent waveforms, to afford the pulse designer an additional spatial encoding mechanism, i.e., transmit sensitivity encoding, that complements gradient encoding. However, in contrast to parallel reception, parallel excitation requires individual high-power amplifiers for each transmit channel, which can be cost-prohibitive. Several groups have explored the use of low-cost transmit amplifiers for parallel excitation, e.g. [1-3], however, such amplifiers commonly exhibit temporal non-idealities that distort the RF waveform. To overcome this problem, we introduce a novel regularization technique for parallel excitation pulse design that yields pulses with smoother magnitude envelopes. We demonstrate experimentally that pulses designed with the new technique suffer less amplifier distortion than unregularized pulses.