Pulse design for joint optimization of semisolid saturation and free water rotation
David Leitão1,2, Raphael Tomi-Tricot1,3, Pip Bridgen1, Tom Wilkinson1, Patrick Liebig4, Rene Gumbrecht4, Dieter Ritter4, Sharon Giles1, Ana Baburamani1, Joseph V. Hajnal1,5, and Shaihan J. Malik1,5
1Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, 2London Collaborative Ultra high field System (LoCUS), London, United Kingdom, 3MR Research Collaborations, Siemens Healthcare Limited, Frimley, United Kingdom, 4Siemens Healthcare GmbH, Erlangen, Germany, 5Centre for the Developing Brain, King's College London, London, United Kingdom
In MT imaging, particularly at ultra-high field, results can be influenced by spatial variations in both (1) on-resonance flip angle and (2) RF saturation specified by B1rms including on- and off-resonance contributions. Conventional pulse design with parallel transmission focuses on homogenizing flip angle (α) distributions but does not explicitly account for B1rms distribution.
In this work we propose a generalized pulse design framework that considers both α and B1rms and apply it to achieve uniform excitation and saturation at the same time. Performance is confirmed in phantom experiments at 7T, resulting in more uniform MTR compared to conventionally-designed pulses.
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