Spiral-GRASP-UTE: 4D Real-Time MRI of the Lung with Sub-Second Temporal Resolution

The purpose of this work was to develop a dynamic lung MRI framework, called Spiral-GRASP-UTE, for 4D real-time imaging of the lung with sub-second temporal resolution. Spiral-GRASP-UTE combines continuous ultra-short echo time (UTE) variable-density stack-of-spirals acquisition with a recently developed GRASP-Pro reconstruction technique that is based on a low-rank subspace model. Compared to other state-of-the-art lung MRI methods using 3D radial Kooshball sampling, Spiral-GRASP-UTE enables fast free-breathing dynamic lung imaging (2-3 minutes) and a high temporal resolution of less than one second per volume. This eliminates the need for respiratory motion detection and compensation, which is often challenging in lung MRI.