Respiratory motion-resolved four-dimensional zero echo time (4D ZTE) lung MRI using retrospective soft gating: feasibility and image quality compared with 3D ZTE

To evaluate the feasibility and image quality of respiratory motion–resolved 4D zero echo time (ZTE) lung MRI compared with that of 3D ZTE. Our institutional review board approved this study. Twenty-one patients underwent lung scans using 3D ZTE and 4D ZTE sequences via prospective and retrospective soft gating techniques, respectively. Image qualities of 3D ZTE and 4D ZTE at end-expiration were compared through objective and subjective assessments. The quality of end-expiratory images of 3D ZTE and 4D ZTE of the two groups with different lung functions was also compared. Images were successfully acquired in all patients without any adverse events. Signal-to-noise ratios (SNRs) of lung parenchyma and thoracic structures were significantly (all p