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Abstract #4257

Design of Non-Selective Refocusing Pulses with Phase-Free Rotation Axis by Gradient Ascent Algorithm in Parallel Transmission at 7 T

Aurlien Massire1, Martijn A. Cloos2, Alexandre Vignaud1, Denis Le Bihan1, Alexis Amadon1, Nicolas Boulant1

1CEA DSV I2BM NEUROSPIN LRMN, Gif-sur-Yvette, France; 2Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, NY, United States

We use gradient ascent pulse engineering combined with the kT-point method to design non-selective refocusing pulses that mitigate severe B1 and ΔB0 inhomogeneities. The novelty of the method lays in the optimization of the relevant rotation matrices themselves rather than magnetization states. Experimental validation was performed on a phantom and using a 7 T scanner equipped with an 8-channel transmit array. The rotation matrix on every voxel was measured using Quantum Process Tomography. In addition, a modified non-selective Spin-Echo sequence was run to evaluate the ability to refocus dephased magnetization. Both experiments confirmed high fidelity of the here-introduced technique.