3D ultrashort echo time MRI of the lung using stack‐of‐spirals and spherical k‐Space coverages: Evaluation in healthy volunteers and parenchymal diseases

Background Ultrashort echo time (UTE) has been shown to improve lung MRI quality in three dimensions. The evaluation of 3D‐UTE stack‐of‐spirals VIBE (3D‐USV) sequence for parenchymal diseases and a comparison of performance with that of a spherical mode of acquisition is needed. Purpose To assess MRI quality using a prototypical 3D‐USV sequence and to compare performance with that of a spherical acquisition using Pointwise Encoding Time Reduction with Radial Acquisition (PETRA). Study Type Monocenter, prospective. Population Twelve healthy volunteers and 32 adult patients with either cystic fibrosis (CF; n = 16) or interstitial lung disease (ILD; n = 16). Field Strength/Sequence Both free‐breathing 3D‐USV and PETRA were completed at 1.5T. Assessment In healthy volunteers, visual analysis of imaging quality was scored using a Likert scale. Quantitative evaluation of apparent signal ratio (Sr) and contrast ratio (Cr) was measured. Patients with CF and ILD completed both computed tomography (CT) and MRI. Depiction of structural alterations was assessed using dedicated clinical scores. All evaluations were done in consensus by two readers. Statistical Tests Comparison of means was assessed using the Wilcoxon signed rank test. Concordance and agreement between CT and MRI were assessed using the intraclass correlation coefficient (ICC) and kappa test. Results In controls, 3D‐USV yielded lower artifacts owing to better automatic respiratory synchronization than PETRA ( P < 0.001). However, Sr and Cr of 3D‐USV were found significantly lower by 2.25‐ and 2.36‐fold, respectively ( P < 0.001). In patients, 3D‐USV and PETRA showed comparable performances to assess airway severity in CF (Bhalla score, ICC = 0.89 and ICC = 0.92, respectively) and presence of structural alterations in ILD such as honeycombing (kappa = 0.68 and kappa = 0.69, respectively). Data Conclusion 3D‐USV enables high‐resolution morphological imaging of the lung without need of an external device to compensate respiratory motions. Automation and robustness of the method may facilitate clinical application for both airway and interstitial lung investigations. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;48:1489–1497