Abstract #3447

Individually optimized dynamic parallel transmit pulses for 3D high-resolution SPACE imaging at 7T

Gian Franco Piredda¹, Emilie Sleight^2,3, Thomas Yu^1,4,5, Antoine Klauser¹, Natalia Pato Montemayor^1,4,5, Jocelyn Philippe^1,4,5, Lina Bacha^1,4,5, Tommaso Di Noto^1,4,5, Bénédicte Maréchal^1,4,5, Patrick A. Liebig⁶, Dominik Nickel⁶, Tobias Kober^1,4,5, Tom Hilbert^1,4,5, Robin M. Heidemann⁶, and Juergen Herrler⁶

¹Advanced Clinical Imaging Technology, Siemens Healthineers International AG, Lausanne, Switzerland, ²Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, ³CIBM Center for Biomedical Imaging, Geneva, Switzerland, ⁴Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland, ⁵LTS5, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, ⁶Siemens Healthineers AG, Erlangen, Germany

Synopsis

Keywords: Parallel Transmit & Multiband, RF Pulse Design & Fields, Ultra-high field MRI, SPACE

Motivation: 3D high-resolution SPACE imaging at 7T suffers from signal dropouts due to inhomogeneous B₁⁺ fields.

Goal(s): To investigate online-optimized pTx pulses for homogenous SPACE brain imaging.

Approach: Non-parametrized pTx pulses were designed for inversion, and, with symmetric RF and gradient shapes, for excitation and refocusing. The pulses are then individually optimized online within a clinically acceptable computation time. T₁-weighted, T₂-weighted, FLAIR and DIR SPACE images were acquired in five healthy subjects at 7T using both circularly polarized (CP) and dynamic pTx pulses for comparison.

Results: Improved flip angle homogeneity was observed in all images acquired with individual pTx pulses as opposed to CP.

Impact: Individually optimized dynamic parallel transmit pulses for 3D high-resolution SPACE imaging at 7T achieve clinically acceptable image homogeneity and acquisition time, enabling the application of widely used clinical contrasts at 7T.

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