Simultaneous feedback control for joint field and motion correction in brain MRI

• Main Authors: Laetitia Vionnet, Alexander Aranovitch, Yolanda Duerst, Maximilian Haeberlin, Benjamin Emmanuel Dietrich, Simon Gross, Klaas Paul Pruessmann
• Format: Article
• Language: English
• Published: Elsevier 2021-02-01
• Series: NeuroImage
• Subjects: Feedback control; Field stabilization; Prospective motion correction; Joint correction; T2*-weighted imaging; High field MRI
• Online Access: http://www.sciencedirect.com/science/article/pii/S1053811920307722

T2*-weighted gradient-echo sequences count among the most widely used techniques in neuroimaging and offer rich magnitude and phase contrast. The susceptibility effects underlying this contrast scale with B0, making T2*-weighted imaging particularly interesting at high field. High field also benefits baseline sensitivity and thus facilitates high-resolution studies. However, enhanced susceptibility effects and high target resolution come with inherent challenges. Relying on long echo times, T2*-weighted imaging not only benefits from enhanced local susceptibility effects but also suffers from increased field fluctuations due to moving body parts and breathing. High resolution, in turn, renders neuroimaging particularly vulnerable to motion of the head. This work reports the implementation and characterization of a system that aims to jointly address these issues. It is based on the simultaneous operation of two control loops, one for field stabilization and one for motion correction. The key challenge with this approach is that the two loops both operate on the magnetic field in the imaging volume and are thus prone to mutual interference and potential instability. This issue is addressed at the levels of sensing, timing, and control parameters. Performance assessment shows the resulting system to be stable and exhibit adequate loop decoupling, precision, and bandwidth. Simultaneous field and motion control is then demonstrated in examples of T2*-weighted in vivo imaging at 7T.