PurposeTo demonstrate free-breathing thoracic MRI with a minimal-TR balanced steady-state free precession (bSSFP) technique using wobbling Archimedean spiral pole (WASP) trajectories.MethodsPhantom and free-breathingin vivochest imaging in healthy volunteers was performed at 1.5T with a half-radial, dual-echo, bSSFP sequence, termed bSTAR. For maximum sampling efficiency, a single analog-to-digital converter window along the full bipolar readout was used. To ensure a homogeneous coverage of the k-space over multiple breathing cycles, radial k-space sampling followed short-duration Archimedean spiral interleaves that were randomly titled by a small polar angle and rotated by a golden angle about the polar axis; depticting a wobbling Archimedean spiral pole (WASP) trajectory. In phantom andin vivoexperiments, WASP trajectories were compared to spiral phyllotaxis sampling in terms of eddy currents and were used to generatein vivothorax images at different respiratory phases.ResultsWASP trajectories provided artifact-free bSTAR imaging in both phantom andin vivoand respiratory self-gated reconstruction was successfully performed in all subjects. The amount of the acquired data allowed the reconstruction of 10 volumes at different respiratory levels with isotropic resolution of 1.77 mm from a scan of 5.5 minutes (using a TR of 1.32ms), and one high-resolution 1.16 mm end-expiratory volume from a scan of 4.7 minutes (using a TR of 1.42ms). The very short TR of bSTAR mitigated off-resonance artifacts despite the large field-of-view.ConclusionWe have demonstrated the feasibility of high-resolution free-breathing thoracic imaging with bSTAR using the wobbling Archimedean spiral pole in healthy subjects at 1.5T.