Shim arrays provide nonlinear, time-varying fields that can extend the possibility of linear gradient field for RF excitations. In this work, we explore the possibility of designing a selective refocusing 180° pulse for a restricted slice pattern of 1.2cm thickness, aimed at application for the fetal brain. We use an auto-differentiable Bloch simulator framework for the design, but without the presentence of crusher gradients. Decomposition property is employed to overcome the undetermined initial magnetization. The selective refocusing profile achieves selective refocusing for 85% of voxels in the ROI (My< -0.9).
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