Objective To investigate the feasibility of strain analysis on four-dimensional dynamic-ventilation CT to quantify lung deformation during ventilation in patients with chronic obstructive pulmonary disease(COPD).Methods Ninety-one patients with COPD underwent pulmonary functional tests,routine low-dose chest CT,and dynamic-ventilation CT using a 320-row CT scanner(Aquilion ONE,Canon Medical Systems).Dynamic-ventilation CT data were continuously reconstructed every 0.2 s to a total of 41 frames in each patient.Strain analysis was performed using a commercial software(Micro Vec V3.6.2,Micorvec Pte Ltd,Beijing)that was originally developed for computational fluid dynamics.Total lung volume and low-density index(percent of the whole lung volume with CT density＜-950 Hounsfield units)were analyzed using a built-in software(Lung Density Analysis,Canon Medical Systems).Spearman rank correlation analysis was used to evaluate the associations between quantitative CT parameters and spirometry.P＜0.05 was considered statistically significant.Results The adjusted strain parameters,especially the maximum principal strain and maximum displacement speed derived from the first 2 s of expiration were significantly correlated with forced expiratory volume in one second/forced vital capacity(ρ=0.623-0.684,P＜0.001),peak expiratory flow(ρ=0.287-0.425,P＜0.05),and maximum mid-expiratory flow rate(ρ=0.481-0.621,P＜0.001).Conclusion Quantitative strain measurement using the dynamic-ventilation CT can reflect pulmonary function changes with impaired lung deformation extent and velocity in patients with COPD.
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