An in-vivo approach to quantify head motion tracking accuracy: comparison of markerless optical tracking versus fat-navigators

Motivation: We propose an approach for evaluating the in-vivo performance of head-motion tracking techniques in MRI. Goal(s): This approach was used to compare a markerless optical-system and a fat-navigator-based strategy (Fat-Nav). Approach: Six participants underwent seven MP-RAGE scans, each with different predefined head positions. Optical-system and Fat-Nav estimates were then compared to a gold-standard. Results: The results showed that the optical-system outperformed Fat-Nav in estimating large amplitude voluntary movements on its principal axes, while Fat-Nav was more accurate for small secondary head-motions. The approach also proved quite effective in detecting Fat-Nav improvement by neck-masking on fat-navigator, demonstrating its value in optimizing head-motion tracking methods. Impact: The proposed approach enables in-vivo evaluation of head-motion tracking in MRI and, consequently, could contribute to improving motion artifact-correction for brain-MRI. Its impact will be substantial with the advent of ultra-high magnetic-field scanners and the widespread use of high-resolution brain-MRI.