Motion guidance lines for robust data consistency–based retrospective motion correction in 2D and 3D MRI

Purpose To develop a robust retrospective motion‐correction technique based on repeating k‐space guidance lines for improving motion correction in Cartesian 2D and 3D brain MRI. Methods The motion guidance lines are inserted into the standard sequence orderings for 2D turbo spin echo and 3D MPRAGE to inform a data consistency–based motion estimation and reconstruction, which can be guided by a low‐resolution scout. The extremely limited number of required guidance lines are repeated during each echo train and discarded in the final image reconstruction. Thus, integration within a standard k‐space acquisition ordering ensures the expected image quality/contrast and motion sensitivity of that sequence. Results Through simulation and in vivo 2D multislice and 3D motion experiments, we demonstrate that respectively 2 or 4 optimized motion guidance lines per shot enables accurate motion estimation and correction. Clinically acceptable reconstruction times are achieved through fully separable on‐the‐fly motion optimizations (˜1 s/shot) using standard scanner GPU hardware. Conclusion The addition of guidance lines to scout accelerated motion estimation facilitates robust retrospective motion correction that can be effectively introduced without perturbing standard clinical protocols and workflows.