Assessment of lung deformation in patients with idiopathic pulmonary fibrosis with elastic registration technique on pulmonary three-dimensional ultrashort echo time MRI

Objective: To assess lung deformation in patients with idiopathic pulmonary fibrosis (IPF) using with elastic registration algorithm applied to three-dimensional ultrashort echo time (3D-UTE) MRI and analyze relationship of lung deformation with the severity of IPF. Methods: Seventy-six patients with IPF (mean age: 62 +/- 6 years) and 62 age- and gender-matched healthy controls (mean age: 58 +/- 4 years) were prospectively enrolled. End-inspiration and end-expiration images acquired with a single breath-hold 3D-UTE sequence were registered using elastic registration algorithm. Jacobian determinants were calculated from deformation fields and represented on color maps. Jac-mean (absolute value of the log means of Jacobian determinants) and the Dice similarity coefficient (Dice) were compared between different groups. Results: Compared with healthy controls, the Jac-mean of IPF patients significantly decreased (0.21 +/- 0.08 vs. 0.27 +/- 0. 07, p < 0.001). Furthermore, the Jac-mean and Dice correlated with the metrics of pulmonary function tests and the composite physiological index. The lung deformation in IPF patients with dyspnea Medical Research Council (MRC) >= 3 (Jac-mean: 0.16 +/- 0.03; Dice: 0.06 +/- 0.02) was significantly lower than MRC1 (Jac-mean: 0. 25 +/- 0.03, p < 0.001; Dice: 0.10 +/- 0.01, p < 0.001) and MRC 2 (Jac-mean: 0.22 +/- 0.11, p = 0.001; Dice: 0.08 +/- 0.03, p = 0.006). Meanwhile, Jac-mean and Dice correlated with health-related quality of life, 6 min-walk distance, and the extent of pulmonary fibrosis. Jac-mean correlated with pulmonary vascular-related indexes on high-resolution CT. Conclusion: The decreased lung deformation in IPF patients correlated with the clinical severity of IPF patients. Elastic registration of inspiratory-to-expiratory 3D UTE MRI may be a new morphological and functional marker for non-radiation and noninvasive evaluation of IPF.