Inspiratory and Expiratory Computed Tomography Imaging Clusters Reflect Functional Characteristics in Chronic Obstructive Pulmonary Disease

Abstract

Purpose

Disease probability measure (DPM) is a useful voxel-wise imaging assessment of gas-trapping and emphysematous lesions in patients with chronic obstructive pulmonary disease (COPD). To elucidate the progression of COPD, we performed a cluster analysis using the following DPM parameters: normal (DPM_Normal), gas-trapping (DPM_GasTrap), and emphysematous lesions (DPM_Emph). Our findings revealed the characteristics of each cluster and the 3-year disease progression using imaging parameters.

Patients and Methods

Inspiratory and expiratory chest computed tomography (CT) images of 131 patients with COPD were examined, of which 84 were followed up for 3 years. The percentage of low attenuation volume (LAV%) and the square root of the wall area of a hypothetical airway with an internal perimeter of 10 mm (√Aaw at Pi10) were quantitatively measured using inspiratory chest CT. A hierarchical cluster analysis was performed using the DPM parameters at baseline. Five clusters were named according to the dominant DPM parameters: normal (NL), normal-GasTrap (NL-GT), GasTrap (GT), GasTrap-Emphysema (GT-EM), and Emphysema (EM).

Results

Women were predominantly diagnosed with GT. Forced expiratory volume in 1 s gradually decreased in the following order: NL, NL-GT, GT, GT-EM, and EM. DPM_Emph correlated well with LAV%. Four clusters other than NL showed significantly higher values of √Aaw at Pi10 than NL; however, no significant differences were observed among them. In all clusters, DPM_Emph increased after 3 years. DPM_Normal only increased in the GT cluster.

Conclusion

Clusters using DPM parameters may reflect the characteristics of COPD and help understand the pathophysiology of the disease.

Keywords:

• cluster analysis
• computed tomography
• COPD
• DPM
• gas-trapping
• emphysema

Abbreviations

√Aaw at Pi10, square root of the wall area of a hypothetical airway with an internal perimeter of 10 mm; ALX, low-frequency reactance; CT, computed tomography; COPD, chronic obstructive pulmonary disease; DPM, disease probability measure; EM, Emphysema cluster; FEV₁, forced expiratory volume in 1s; FOT, forced oscillation technique; Fres, resonant frequency; FVC, forced vital capacity; GOLD, Global Initiative for Chronic Obstructive Lung Disease; GT, GasTrap cluster; GT-EM, GasTrap-Emphysema cluster; LABA, long-acting β2 agonist; LAV%, low attenuation volume; LAMA, long-acting muscarinic antagonist; NL, normal cluster; NL-GT, Normal-GasTrap cluster; PRM, parametric response mapping; Rrs, respiratory system resistance; Xrs, respiratory system reactance.

Data Sharing Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Ethics Approval and Informed Consent

This study was approved by the Ethics Committee of SUMS (registration number: 27-11) and conformed to the tenets of the Declaration of Helsinki, and all participants provided written informed consent prior to their participation.

Acknowledgments

The authors would like to thank Yoko Naito, Yukie Miyatake, Yasutaka Horii, Makoto Yamasaki, and Fuko Kikuchi for their continued help throughout the study.

Author Contributions

YM and EO conceived the idea of the study. All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.

Additional information

Funding

This work was supported by JSPS KAKENHI Grant Number JP 22K16189.