Strain measurement on four-dimensional dynamic-ventilation CT: quantitative analysis of abnormal respiratory deformation of the lung in COPD

Abstract

Purpose

Strain measurement is frequently used to assess myocardial motion in cardiac imaging. This study aimed to apply strain measurement to pulmonary motion observed by four-dimensional dynamic-ventilation computed tomography (CT) and to clarify motion abnormality in COPD.

Materials and methods

Thirty-two smokers, including ten with COPD, underwent dynamic-ventilation CT during spontaneous breathing. CT data were continuously reconstructed every 0.5 seconds. In the series of images obtained by dynamic-ventilation CT, five expiratory frames were identified starting from the peak inspiratory frame (first expiratory frame) and ending with the fifth expiratory frame. Strain measurement of the scanned lung was performed using research software that was originally developed for cardiac strain measurement and modified for assessing deformation of the lung. The measured strain values were divided by the change in mean lung density to adjust for the degree of expiration. Spearman’s rank correlation analysis was used to evaluate associations between the adjusted strain measurements and various spirometric values.

Results

The adjusted strain measurement was negatively correlated with FEV₁/FVC (ρ=−0.52, P<0.01), maximum mid-expiratory flow (ρ=−0.59, P<0.001), and peak expiratory flow (ρ=−0.48, P<0.01), suggesting that abnormal deformation of lung motion is related to various patterns of expiratory airflow limitation.

Conclusion

Abnormal deformation of lung motion exists in COPD patients and can be quantitatively assessed by strain measurement using dynamic-ventilation CT. This technique can be expanded to dynamic-ventilation CT in patients with various lung and airway diseases that cause abnormal pulmonary motion.

Keywords:

• COPD
• computed tomography
• CT
• dynamic-ventilation CT
• strain measurement
• emphysema

Acknowledgments

The authors greatly thank Mr Shun Muramatsu (Ohara General Hospital) for his great help in scanning patients. The authors also thank Dr Shinsuke Tsukagoshi (Canon 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); University of Occupational and Environmental Health, Kitakyushu, Fukuoka, Japan (Takatoshi Aoki, MD, PhD); University of the Ryukyus, Nishihara, Okinawa, Japan (Tsuneo Yamashiro, MD, Maho Tsubakimoto, MD, PhD, Yanyan Xu, MD, Sadayuki Murayama, MD, PhD). University of the Ryukyus, Ohara General Hospital, and Shiga University of Medical Science receive a research grant from Canon Medical Systems (formerly Toshiba Medical Systems). University of the Ryukyus also receives a research grant from Ziosoft. Xu Y receives a scholarship (Sasagawa scholarship) from the Japan China Medical Association. Yamashiro T received a research grant from the Japan Society for the Promotion of Science (Kakenhi-16K19837).

Disclosure

The authors report no conflicts of interest in this work.