Abstract: Simultaneous multi-slice magnetic resonance imaging (MRI) has attracted much research interests recently due to its advantages in increasing signal-to-noise ratio (SNR) and decreasing acquisition time. To achieve simultaneous multi-slice excitation, the existing methods used a composite excitation pulse, yielded from the linear combination of radio frequency (RF) pulses with the same amplitude but different phases. The performance of such composite pulse, however, is limited, due to the square relationship between the peak pulse power and slice number. To solve this problem, we proposed a numerical optimization method for multi-slice excitation RF pulse based on both spin dynamics and optimal control theory. Together with slice selection gradient, the optimized pulse achieved selective excitation with arbitrary thickness, distance and number of slices. The performance of the optimized pulse in simultaneous multi-slice MRI was validated by simulation on multimodal imaging-based detailed anatomical (MIDA) digital phantom.

Key words: simultaneous multi-slice MRI, optimal control, numerical optimization, excitation profile