Abstract #3440

Evaluation of the effects of motion on dynamic pTx pulse optimization at 7T

Jocelyn Philippe^1,2,3, Natalia Pato Montemayor^1,2,3, Antoine Klauser¹, Emilie Sleight^4,5, Patrick A. Liebig⁶, Jürgen Herrler⁶, Robin M. Heidemann⁶, Tobias Kober⁷, Jean-Philippe Thiran^2,3, Tom Hilbert^1,2,3, Gian Franco Piredda¹, and Thomas Yu^1,2,3

¹Advanced Clinical Imaging Technology, Siemens Healthineers International AG, Lausanne, Switzerland, ²Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland, ³LTS5, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, ⁴CIBM Center for Biomedical Imaging, Lausanne, Switzerland, ⁵Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, ⁶Siemens Healthineers AG, Erlangen, Germany, ⁷Siemens Healthineers AG, Forchheim, Germany

Synopsis

Keywords: RF Pulse Design & Fields, System Imperfections: Measurement & Correction, 7T, Motion, Dynamic pTx

Motivation: The performance of dynamic pTx pulses might be affected by patient motion, especially in the case of long scanning sessions.

Goal(s): To examine the actual impact of motion on the flip angle map of a pTx pulse optimized with a fast online customization (FOCUS) strategy.

Approach: B₀ and multi-channel B₁⁺ maps were acquired at multiple head positions, and the application of the pulse optimized on the first position was simulated on the subsequent positions.

Results: For various ranges of motion measured in this study, FOCUS pTx pulses are demonstrated to be robust to motion occurring after the acquisition of the field maps.

Impact: Fast online customized pTx pulses suffer from motion during long scanning sessions, mainly due to changes in B₁⁺ field distribution. However, for motion amplitudes comparable to what was measured, the negative impact on low flip angle non-selective pulses is negligible.

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