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