Motion-Resolved 4D MRI using Vision-Assisted Reference Auto-Navigation

Improved motion navigation with efficient data usage and robustness remains a challenge for free-breathing MRI. This paper presents a new 2D auto-navigation technique called VAR-NAV developed for stack-of-stars acquisitions to address this challenge. VAR-NAV uses 2D projection images and multiscale AM-FM demodulation to directly estimate the position of the liver dome with 100% data efficiency. Results can be retrospectively corrected, similar to the VAR system in football video assistant referees. VAR-NAV is used to continuously sort acquired data and reconstruct motion-resolved 4D images, outperforming conventional ID PCA-based navigation without requiring additional acquisition. This efficient and accurate method of clinical 4D MRI offers a promising solution to the challenge of improved motion navigation.