Surface Tracking-assisted Real-time 4D Lung MRI

Motivation: To develop a continuous 4D lung MRI technique that captures intra- and inter-cycle variability to enable motion modeling for real-time target tracking for radiotherapy. Goal(s): To address the challenge of acquiring sufficient data for reconstruction of dynamic 3D volumes while maintaining adequate spatiotemporal resolution for radiation therapy guidance. Approach: We utilized golden angle stack-of-star acquisition, and labeled each view with continuous breathing state from a surface tracking system for sharing views with similar breathing states. Results: Continuous 4D lung MRI at 60.6ms per volume with high spatial resolution that shows movement of lung vessels. Impact: Continuous 4D lung MRI allows accurate modeling of respiration-induced internal target motion to surface motion prior to radiotherapy, and thus enables real-time target tracking during external beam radiation treatment without the need of MR linac.