Abstract
Objective: To provide the quantitative volumetric data of the total lung and lobes in inspiration and expiration from healthy adults, and to explore the value of paired inspiratory–expiratory chest CT scan in pulmonary ventilatory function and further explore the influence of each lobe on ventilation. Methods: A total of 65 adults (29 males and 36 females) with normal clinical pulmonary function test (PFT) and paired inspiratory–expiratory chest CT scan were retrospectively enrolled. The inspiratory and expiratory volumetric indexes of the total lung (TL) and 5 lobes (left upper lobe [LUL], left lower lobe [LLL], right upper lobe [RUL], right middle lobe [RML], and right lower lobe [RLL]) were obtained by Philips IntelliSpace Portal image postprocessing workstation, including inspiratory lung volume (LVin), expiratory lung volume (LVex), volume change (∆LV), and well-aerated lung volume (WAL, lung tissue with CT threshold between −950 and −750 HU in inspiratory scan). Spearman correlation analysis was used to explore the correlation between CT quantitative indexes of the total lung and ventilatory function indexes (including total lung capacity [TLC], residual volume [RV], and force vital capacity [FVC]). Multiple stepwise regression analysis was used to explore the influence of each lobe on ventilation. Results: At end-inspiratory phase, the LVin-TL was 4664.6 (4282.7, 5916.2) mL, the WALTL was 4173 (3639.6, 5250.9) mL; both showed excellent correlation with TLC (LVin-TL: r = 0.890, p < 0.001; WALTL: r = 0.879, p < 0.001). From multiple linear regression analysis with lobar CT indexes as variables, the LVin and WAL of these two lobes, LLL and RUL, showed a significant relationship with TLC. At end-expiratory phase, the LVex-TL was 2325.2 (1969.7, 2722.5) mL with good correlation with RV (r = 0.811, p < 0.001), of which the LVex of RUL and RML had a significant relationship with RV. For the volumetric change within breathing, the ∆LVTL was 2485.6 (2169.8, 3078.1) mL with good correlation with FVC (r = 0.719, p < 0.001), moreover, WALTL showed a better correlation with FVC (r = 0.817, p < 0.001) than that of ∆LVTL. Likewise, there was also a strong association between ∆LV, WAL of these two lobes (LLL and RUL), and FVC. Conclusions: The quantitative indexes derived from paired inspiratory–expiratory chest CT could reflect the clinical pulmonary ventilatory function, LLL, and RUL give greater impact on ventilation. Thus, the pulmonary functional evaluation needs to be more precise and not limited to the total lung level.
Highlights
Chest computed tomography (CT) is a well-known imaging method for displaying the pulmonary morphological state for qualitative evaluation; it has the potential to reflect the histopathological or functional status combined with quantitative analysis
The area where the CT value lower than −950 hounsfield units (HU) at endinspiratory scanning is considered as emphysema tissue, which has been confirmed by histopathology [1]; the area below −856HU at end-expiratory scanning is considered as air trapping [2,3]; a quantitative CT can be used to evaluate small airway diseases when combined with airway-wall measurements so as to explain the presence of respiratory symptoms beyond the information offered by the clinical pulmonary function test (PFT) [4,5]
The paired inspiratory–expiratory chest CT has been studied in chronic obstructive pulmonary disease (COPD), which is characterized by incompletely reversible airflow limitation for further exploration [6,7]
Summary
Chest computed tomography (CT) is a well-known imaging method for displaying the pulmonary morphological state for qualitative evaluation; it has the potential to reflect the histopathological or functional status combined with quantitative analysis. The area where the CT value lower than −950 hounsfield units (HU) at endinspiratory scanning is considered as emphysema tissue, which has been confirmed by histopathology [1]; the area below −856HU at end-expiratory scanning is considered as air trapping [2,3]; a quantitative CT can be used to evaluate small airway diseases when combined with airway-wall measurements so as to explain the presence of respiratory symptoms beyond the information offered by the clinical pulmonary function test (PFT) [4,5]. Zach et al [8] reported that the volume change and mean lung density of upper lobes and lower lobes within a respiratory cycle were different, which suggests that the pulmonary functional imaging is far from enough at the total-lung level. It is feasible to segment and analyze the pulmonary lobe independently with the fast development of high-resolution CT and image postprocessing technology
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