Asynchronous changes of normal lung lobes during respiration based on quantitative computed tomography (CT)

Feihong Wu; Congping Lin; Leqing Chen; Jia Huang; Wenliang Fan; Zhuang Nie; Yiwei Zhang; Wanting Li; Jiazheng Wang; Fan Yang; Chuansheng Zheng

doi:10.21037/qims-21-348

Asynchronous changes of normal lung lobes during respiration based on quantitative computed tomography (CT)

Quant Imaging Med Surg. 2022 Mar;12(3):2018-2034. doi: 10.21037/qims-21-348.

Authors

Feihong Wu^#^{1

2}, Congping Lin^#³, Leqing Chen^#^{1

2}, Jia Huang^{1

2}, Wenliang Fan^{1

2}, Zhuang Nie^{1

2}, Yiwei Zhang³, Wanting Li³, Jiazheng Wang⁴, Fan Yang^{1

2}, Chuansheng Zheng^{1

2}

Affiliations

¹ Department of Radiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
² Hubei Province Key Laboratory of Molecular Imaging, Wuhan, China.
³ School of Mathematics and Statistics, Center for Mathematical Science, Hubei Key Laboratory of Engineering Modeling and Scientific Computing, Huazhong University of Science and Technology, Wuhan, China.
⁴ MSC Clinical & Technical Solutions, Philips Healthcare, Beijing, China.

^# Contributed equally.

Abstract

Background: This study aimed to explore the coordinated and independent actions of lung lobes during respiration using quantitative computed tomography (CT) in order to increase our in vivo understanding of pulmonary anatomy.

Methods: Cases for whom test results showed normal pulmonary function tests (PFTs) results, and normal paired inspiratory-expiratory chest CT findings, as assessed by 2 radiologists, were retrospectively included in this study. From the chest CT results, we measured quantitative indices of lung volume (LV) and mean lung density (MLD) for the total lung (TL), left lung (LL), right lung (RL), and 5 lobes in inspiratory and expiratory phases. The differences of these measures between bilateral lungs and among the lobes were evaluated to study whether they were consistent or different during respiration.

Results: A total of 70 cases were included {median age of 49.5 [interquartile range (IQR), 38.0 to 60.3] years; 32 males; 38 females}. Overall, the inspiratory and expiratory volumes of the LL were smaller than those of the RL (both P<0.001). For the ventilation workload (λ, which indicates the ratio of lobar volume to total LV), the end-expiratory volume ratio (λ_ex ) of the LL was 0.44 (IQR, 0.43 to 0.46), while the end-inspiratory volume ratio (λ_in ) had risen to 0.46 (IQR, 0.45 to 0.47) (P<0.001). Comparing the 5 lobes, not all lobes shared the same LV. However, the left lower lobe (LLL) and right lower lobe (RLL) showed some similarities. The λ_in-LLL and λ_in-RLL was higher than λ_ex-LLL and λ_ex-RLL , respectively (both P<0.001), while the ratios of the other lobes reduced. The pairwise mean absolute difference (PMAD) on λ_in and λ_ex of the bilateral lower lobes was low in inspiration (0.0288) and expiration (0.0346). The MLD of bilateral lower lobes showed consistency in inspiration or in expiration (inspiration: P>0.999; expiration: P=0.975). In addition, the PMADs between the right middle lobe (RML) and other lobes were significantly larger than the PMAD between other pairs of lobes in both inspiration and expiration. Beyond that, the expiratory MLD of RML [-789.6 (IQR, -814 to -762.05) HU] was the lowest among the 5 lobes.

Conclusions: We found that the LL assumes a higher workload during ventilation than it does during respiration. The 5 normal lobes were non-synchronous during respiration and contributed differently to ventilation. The bilateral lower lobes showed similarities and had a high-ventilation function, while and the LV and MLD of the RML showed the least changes within a respiration cycle.

Keywords: Quantitative computed tomography (CT); pulmonary anatomy; pulmonary ventilation function; respiration.