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Abstract #4062

Selective Refocusing Pulse Design via Time-varying Nonlinear Shim Array Fields and RF Pulse with Decomposition Property

Molin Zhang1, Nicolas Arango1, Jason Stockmann2, Jacob White1, and Elfar Adalsteinsson1,3,4
1EECS, MIT, Cambridge, MA, United States, 2Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 3Harvard-MIT Health Sciences and Technology, MIT, Cambridge, MA, United States, 4Institute for Medical Engineering and Science, MIT, Cambridge, MA, United States


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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