Multiphoton Excitation Enabled Simultaneous Multislice Parallel Transmission at 7T

Motivation: Simultaneous multislice (SMS) acquisitions are beneficial for high-resolution scans at ultrahigh field (UHF), however, they are limited by transmit $$$B_1\:(B_1^+)$$$ inhomogeneity and high specific absorption rate (SAR). Goal(s): To utilize multiphoton excitation for reducing $$$B_1^+$$$ inhomogeneity and SAR for SMS at UHF. Approach: We optimize the RF shim coefficients of Multiphoton SMS pulses using magnitude least squares optimization and transmit sensitivity maps at 7T. We evaluate the performance of Multiphoton SMS pTx with Bloch simulations. Results: Multiphoton SMS achieves comparable $$$B_1^+$$$ homogeneity to Full pTx MB while reducing the total RF power by up to 28% for three slices and 47% for five. Impact: This work demonstrates the effectiveness of combining Multiphoton SMS with pTx, achieving comparable homogeneity to Full pTx MB while reducing RF power requirements. Multiphoton SMS pTx provides a promising approach for more efficient and safer SMS excitation at ultrahigh fields.