Minimizing SAR for SNR-Efficient Pseudo-Continuous Arterial Spin Labeling at 7T

Interest in 7T PCASL is increasing due to the large potential increases in SNR. However, PCASL is a relatively high SAR technique, requiring TRs to be extended with deadtime at 7T, which reduces SNR-efficiency and some of the benefit of moving to 7T. Here, we demonstrate that using VERSE to reduce the SAR of both the PCASL and background suppression pulses can reduce TRs by almost 25%, leading to an improvement in tSNR-efficiency compared to an equivalent non-VERSE scan. We reduced the off-resonance sensitivity that VERSE introduces to the background suppression pulses by carefully optimizing the phase waveform.