Effects of Prospective Motion Correction on Perivascular Spaces at 7T MRI Evaluated Using Motion Artifact Simulation

Purpose Prospective motion correction (PMC) is a promising method in mitigating motion artifacts in MRI. However, its effectiveness in improving the visibility of vessel-like thin structures in routine studies is unclear. In this study, we aim to demonstrate the ability of fat-navigator based PMC in improving the visibility of perivascular spaces (PVS) using data from two earlier studies. Methods Two open source MRI data set were used for motion artifact simulation and evaluating PMC, which consist of 66 T2-weighted images without PMC and 38 T2-weighted images with PMC. PMC was performed by adjusting field of view during scan based on motion parameters derived from fat navigators. Motion artifact simulation was performed by misplacing k-space data at a motion-related non-cartesian grid onto the cartesian grid calculated using motion-free images to generate the images without effects of PMC. The simulation’s ability to reproduce motion-induced blurring and ringing artifacts was evaluated using the sharpness at the lateral ventricle/white matter (WM) boundary and the magnitude of ringing artifact component in the Fourier spectrum. PVS volume fraction in WM was employed to reflect its visibility. Sharpness, magnitude of ringing artifact and PVS volume fraction were then compared between simulated images and real images with and without PMC. Results The consistencies in sharpness (rho ≥ 0.86, corrected p ≤ 4.4 ×10 -16 ) and ringing artifact magnitude (rho ≥ 0.42, corrected p ≤ 0.001) were found between simulated images and real images without PMC. There was a significant negative correlation (rho ≤ -0.27, corrected p ≤ 0.08) between PVS volume fraction and motion severity in both simulated and real images without PMC. PMC removed the above correlations (rho ≥ -0.02, corrected p > 1) and increased the boundary sharpness compared to the images simulated using the same motion traces. Conclusions Motion artifact simulation can reproduce the desired motion-induced artifacts on images. PMC reduces the negative impacts of motion on image quality and improves PVS visibility.