Accelerated 2D Cartesian MRI with an 8-channel local B0 coil array combined with parallel imaging

Motivation: The inherently slow MRI scans can be accelerated through rapid modulation of nonlinear gradient fields; however, its fundamental mechanisms and limits remain incompletely understood and validated. Goal(s): We investigate accelerated MRI with flexible modulations of nonlinear B0 fields using a custom-built local B0 array. Approach: The sampling theory is extended to rigorously compare nonlinear field modulation schemes in a quantitative k-space. A novel field calibration technique is proposed to enhance reconstruction. With safety evaluations, we perform in-vivo accelerated scans. Results: Our in-vivo 2D FLASH scans make significant steps to speed up MRI with local B0 array, achieving eight-fold joint acceleration with parallel imaging. Impact: For the first time, the sampling efficiency of nonlinear gradients in the entire k-space is quantitatively visualized, allowing rigorous comparison of distinct B0 modulations. Furthermore, the field estimation technique enables fast and robust in-vivo scans accelerated by flexible nonlinear fields.