Subspace modeling enables time-efficient B1-corrected volumetric water-specific relaxometry with a long echo train CASPR trajectory

Motivation: The acquisition time of volumetric relaxometry techniques is constrained by the sampling efficiency and confounding factors such as fat or the B1 inhomogeneity. Goal(s): To develop a method for volumetric T1- and T2-mapping that improves efficiency while accounting for confounding factors. Approach: A Cartesian acquisition with spiral profile ordering is employed to increase sampling efficiency. A subspace reconstruction is proposed to perform B1- and water-specific T1- and T2-mapping considering the exact k-space sampling pattern. Results: Simulation, phantom and in-vivo experiments were performed to evaluate the proposed method with regard to its quantification performance and its B1 sensitivity at 3T. Impact: Subspace reconstruction in combination with a CASPR trajectory can improve the scan's efficiency and sampling flexibility while correcting for confounders such as fat or B1. The technique may be valuable to develop volumetric relaxometry in clinically acceptable scan times.