Quantitative Emphysema Measurement On Ultra-High-Resolution CT Scans

Abstract

Purpose

To evaluate the advantages of ultra-high-resolution computed tomography (U-HRCT) scans for the quantitative measurement of emphysematous lesions over conventional HRCT scans.

Materials and methods

This study included 32 smokers under routine clinical care who underwent chest CT performed by a U-HRCT scanner. Chronic obstructive pulmonary disease (COPD) was diagnosed in 13 of the 32 participants. Scan data were reconstructed by 2 different protocols: i) U-HRCT mode with a 1024×1024 matrix and 0.25-mm slice thickness and ii) conventional HRCT mode with a 512×512 matrix and 0.5-mm slice thickness. On both types of scans, lesions of emphysema were quantitatively assessed as percentage of low attenuation volume (LAV%, <−950 Hounsfield units). LAV% values determined for scan data from the U-HRCT and conventional HRCT modes were compared by the Wilcoxon matched-pairs signed rank test. The association between LAV% and forced expiratory volume in 1 s per forced vital capacity (FEV₁/FVC) was assessed by the Spearman rank correlation test.

Results

Mean values for LAV% determined for the U-HRCT and conventional HRCT modes were 8.9 ± 8.8% and 7.3 ± 8.4%, respectively (P<0.0001). The correlation coefficients for LAV% and FEV₁/FVC on the U-HRCT and conventional HRCT modes were 0.50 and 0.49, respectively (both P<0.01).

Conclusion

Compared with conventional HRCT scans, U-HRCT scans reveal emphysematous lesions in greater detail, and provide slightly increased correlation with airflow limitation.

Keywords:

• chronic obstructive pulmonary disease
• computed tomography
• emphysema
• ultra-high-resolution CT
• quantitative measurement

Acknowledgments

The authors thank Mr Kenji Fujii (Canon Medical Systems) for his technical support.

Disclosure

The University of the Ryukyus and Ohara General Hospital receive a research grant from Canon Medical Systems. Ynayan Xu receives a scholarship (Sasagawa scholarship) from the Japan-China Medical Association. Tsuneo Yamashiro reports a grant from Canon Medical Systems during the conduct of the study, and grants from Ziosoft and JSR outside the submitted work. Sadayuki Murayama reports a research grant from Canon Medical Systems during the conduct of the study. The authors report no other conflicts of interest for this work.