Kurtosis and skewness of density histograms on inspiratory and expiratory CT scans in smokers

Tsuneo Yamashiro, Shin Matsuoka, Raúl San José Estépar, Brian J. Bartholmai, Alejandro Diaz, James C. Ross, Sadayuki Murayama, Edwin K. Silverman, Hiroto Hatabu, George R. Washko

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


The aim of this study is to evaluate the relationship between lung function and kurtosis or skewness of lung density histograms on computed tomography (CT) in smokers. Forty-six smokers (age range 46-81 years), enrolled in the Lung Tissue Research Consortium, underwent pulmonary function tests (PFT) and chest CT at full inspiration and full expiration. On both inspiratory and expiratory scans, kurtosis and skewness of the density histograms were automatically measured by open-source software. Correlations between CT measurements and lung function were evaluated by the linear regression analysis. Although no significant correlations were found between inspiratory kurtosis or skewness and PFT results, expiratory kurtosis significantly correlated with the following: the percentage of predicted value of forced expiratory volume in the first second (FEV1), the ratio of FEV1 to forced vital capacity (FVC), and the ratio of residual volume (RV) to total lung capacity (TLC) (FEV1%predicted, R =-0.581, p < 0.001; FEV1/FVC, R =-0.612, p < 0.001; RV/TLC, R = 0.613, p < 0.001, respectively). Similarly, expiratory skewness showed significant correlations with PFT results (FEV1%predicted, R =-0.584, p < 0.001; FEV1/FVC, R =-0.619, p < 0.001; RV/TLC, R = 0.585, p < 0.001, respectively). Also, the expiratory/inspiratory (E/I) ratios of kurtosis and skewness significantly correlated with FEV1%predicted (p < 0.001), FEV1/FVC (p < 0.001), RV/TLC (p < 0.001), and the percentage of predicted value of diffusing capacity for carbon monoxide (kurtosis E/I ratio, p = 0.001; skewness E/I ratio, p = 0.03, respectively). We conclude therefore that expiratory values and the E/I ratios of kurtosis and skewness of CT densitometry reflect airflow limitation and air-trapping. Higher kurtosis or skewness on expiratory CT scan indicates more severe conditions in smokers.

Original languageEnglish (US)
Pages (from-to)13-20
Number of pages8
JournalCOPD: Journal of Chronic Obstructive Pulmonary Disease
Issue number1
StatePublished - Feb 2011


  • Airflow limitation
  • Chronic obstructive pulmonary disease
  • Computed tomography
  • Density histogram
  • Pulmonary emphysema

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine


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