ΔB₀ Field Control in High Field MRI with Local Multcoil Shim Arrays

Abstract

Local multicoil ΔB₀ shim arrays enable low-cost, simple to fabricate, and physically small, static magnetic field control in magnetic resonance imaging. The presented thesis will show frameworks for coil current calculation for homogeneity and novel selective excitation applications. As MRI RF coils trend towards repositionable and flexible systems for their ease of use and tight-to-the-patient fit, ΔB₀ shim arrays are left behind for lack of rapid, patient-on-the-table calibration. We show an inverse problem approach with physics-based regularization and adaptation to accelerate calibration by over 50 fold. The numerical tools developed for calibration also proved useful for design to enable novel upper bounds on ΔB₀ shim performance and new tools for automatic application and anatomy-specific local multicoil array design.