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

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Abstract
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.

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