Balanced steady-state free precession thoracic imaging with half-radial dual-echo readout on smoothly interleaved archimedean spirals

Purpose To investigate the prospects of a minimal-TR half-radial dual-echo balanced steady-state free precession (bSSFP) acquisition for high-resolution and artifact-free thoracic imaging at 1.5T. Methods Feasibility of bSSFP imaging using isotropic half-radial dual-echo (hr-de) projections with TE1/TE2/TR of 0.12/1.18/1.39 ms acquired along Archimedean spiral trajectories was demonstrated for phantoms and in vivo thorax scans at 1.5T. The centered-out projection offers an ultra-short echo (UTE) comparable to contemporary spoiled gradient echo (SPGR) UTE radial acquisitions used for the assessment of chest morphology. Signal intensities of hr-de-bSSFP were measured and compared to UTE-SPGR in a phantom and for parenchyma and blood in vivo and compared to theory. Results For the lung parenchyma and the blood, hr-de-bSSFP provided more than 4 times higher signal intensity than contemporary UTE-SPGR imaging. The measured hr-de-bSSFP and UTE-SPGR signal ratios were in the agreement with theoretically simulated values. Overall, the very short TR of hr-de-bSSFP successfully mitigated off-resonance artifacts offering high-quality breath-hold thoracic imaging at isotropic resolution of 1.7 mm. The application of a smooth interleaved spiral trajectory for half-radial readouts improved the robustness of hr-de-bSSFP to cardiac motion. Conclusion Thoracic hr-de-bSSFP offers artifact-free chest images with considerably improved signal intensity as compared to contemporary UTE-SPGR imaging at 1.5T.