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Abstract #4329

MPgCG: An Iterative RF Pulse Design Method for Excitation using Nonlinear Gradient Fields

Emre Kopanoglu 1 , Leo K. Tam 1 , Haifeng Wang 1 , and Robert Todd Constable 1

1 Dept. Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut, United States

Spatial encoding functions (SEFs) generated using nonlinear gradient fields (NLGFs) have curved spatial patterns. In Cartesian coordinates, such SEFs are non-orthogonal, which may lead to undesired flip-angle variations in excitation profiles. Although such effects can be suppressed using coordinate transformations, such a transformation may introduce loss-of-detail and introduce undesired constraints on RF pulse design. In this study, an iterative method that utilizes Matching-Pursuit and Conjugate-Gradient algorithms to design RF pulses in Cartesian coordinates is proposed. The method is compared to MP and CG algorithms, as well as non-iterative pulse design using nonlinear coordinate transformations, using simulations.

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