Asynchrony in respiratory movements between the pulmonary lobes in patients with COPD: continuous measurement of lung density by 4-dimensional dynamic-ventilation CT

Abstract

Purpose

Four-dimensional dynamic-ventilation CT imaging demonstrates continuous movement of the lung. The aim of this study was to assess the correlation between interlobar synchrony in lung density and spirometric values in COPD patients and smokers, by measuring the continuous changes in lung density during respiration on the dynamic-ventilation CT.

Materials and methods

Thirty-two smokers, including ten with COPD, underwent dynamic-ventilation CT during free breathing. CT data were continuously reconstructed every 0.5 sec. Mean lung density (MLD) of the five lobes (right upper [RU], right middle [RM], right lower [RL], left upper [LU], and left lower [LL]) was continuously measured by commercially available software using a fixed volume of volume of interest which was placed and tracked on a single designated point in each lobe. Concordance between the MLD time curves of six pairs of lung lobes (RU-RL, RU-RM, RM-RL, LU-LL, RU-LU, and RL-LL lobes) was expressed by cross-correlation coefficients. The relationship between these cross-correlation coefficients and the forced expiratory volume in one second/forced vital capacity (FEV_1.0/FVC) values was assessed by Spearman rank correlation analysis.

Results

In all six pairs of the pulmonary lobes, the cross-correlation coefficients of the two MLD curves were significantly positively correlated with FEV_1.0/FVC (ρ =0.60–0.73, P<0.001). The mean value of the six coefficients strongly correlated with FEV_1.0/FVC (ρ =0.80, P<0.0001).

Conclusion

The synchrony of respiratory movements between the pulmonary lobes is limited or lost in patients with more severe airflow limitation.

Keywords:

• computed tomography
• chronic obstructive pulmonary disease
• emphysema
• airflow limitation
• mean lung density

Supplementary material

Acknowledgments

University of the Ryukyus, Ohara General Hospital, and Shiga University of Medical Science received a research grant from Toshiba Medical Systems. University of the Ryukyus also received a research grant from Ziosoft Inc.

This retrospective study was arranged as part of the Area-detector Computed Tomography for the Investigation of Thoracic Diseases (ACTIve), a multicenter research alliance in Japan. The authors thank Mr Shinsuke Tsukagoshi, Mr Tatsuya Kimoto, (Toshiba Medical Systems), and Mr Yasuhiro Kondo (Ziosoft) for their technical support.

The ACTIve Study Group currently consists of the following institutions:

Ohara General Hospital, Fukushima-City, Fukushima, Japan (Kotaro Sakuma, MD, Hiroshi Moriya, MD, PhD); Saitama International Medical Center, Saitama Medical University, Hidaka, Saitama, Japan (Fumikazu Sakai, MD, PhD); Kanagawa Cardiovascular and Respiratory Center, Yokohama, Kanagawa, Japan (Tae Iwasawa, MD, PhD); Shiga University of Medical Science, Otsu, Shiga, Japan (Yukihiro Nagatani, MD, Norihisa Nitta, MD, Kiyoshi Murata, MD); Osaka University, Suita, Osaka, Japan (Masahiro Yanagawa, MD, PhD, Osamu Honda, MD, PhD, Noriyuki Tomiyama, MD, PhD); Osaka Medical College, Takatsuki, Osaka, Japan (Mitsuhiro Koyama, MD, PhD); Tenri Hospital, Tenri, Nara, Japan (Yuko Nishimoto, MD, Satoshi Noma, MD, PhD); Kobe University, Kobe, Hyogo, Japan (Yoshiharu Ohno, MD, PhD); Okayama University, Okayama-City, Okayama, Japan (Katsuhide Kojima, MD); University of the Ryukyus, Nishihara, Okinawa, Japan (Tsuneo Yamashiro, MD, Yanyan Xu, MD, Maho Tsubakimoto, MD, Nanae Tsuchiya, MD, PhD, Sadayuki Murayama, MD, PhD).

Disclosure

Dr Yamashiro receives a research grant from the Japan Society for the Promotion of Science (Kakenhi-16K19837). The authors report no conflicts of interest in this work.