Abstract #0783

Inner Volume Excitation via Joint Design of Time-varying Nonlinear Shim-array Fields and RF Pulse

Molin Zhang¹, Nicolas Arango¹, Jason Stockmann², Jacob White¹, and Elfar Adalsteinsson^1,3,4

¹Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, ²Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ³Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States, ⁴Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, United States

Inner volume excitation is a promising technique to save scanning time or improve spatial resolution. Shim arrays provide nonlinear fields that extend the possibility of RF excitation of complicated spatial patterns. Yet previous work only employed static non-linear B field and predefined RF pulse which limits the performance. Validated on a fairly difficult tailored 3d volume pattern, jointly designed time-varying nonlinear B field and RF pulse within the auto-differentiable Bloch simulator framework shows substantial improvements. The accuracy improves 62% in terms of L2 norm with incorporated constraints on available RF pulse power.

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