Lung T2 mapping using radial turbo spin echo with respiratory gating using XD-GRASP

Motivation: Radial turbo spin echo has been used for T2 mapping in the lungs. Radial encoding makes it robust to motion and allows for arbitrary assembly of echoes to adjust T2 weighting and select respiratory states. Goal(s): To improve respiratory gating using XD-GRASP. Approach: Images were first reconstructed from individual echo trains and the diaphragm position determined from these. The diaphragm position was then used to sort projections, reconstruct at different TEs and fit T2 maps. Results: Gating using XD-GRASP took longer than using the k-space center but produced clearer gated images. Impact: Radial TSE has both the advantage that each projection contains the k-space center which can be used for gating and that projections can be assembled arbitrarily. The latter can be exploited to derive more precise and robust respiratory positions.