A size-based emphysema severity index: robust to the breath-hold-level variations and correlated with clinical parameters

International Journal of Chronic Obstructive Pulmonary Disease, Aug 2016

A size-based emphysema severity index: robust to the breath-hold-level variations and correlated with clinical parameters Jeongeun Hwang,1 Minho Lee,2 Sang Min Lee,2 Sang Young Oh,2 Yeon-Mok Oh,3,4 Namkug Kim,2,3,* Joon Beom Seo2,* 1Asan Institute for Life Sciences, 2Department of Radiology, 3Department of Convergence Medicine, 4Department of Pulmonary and Critical Care Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea *These authors contributed equally to this work Objective: To determine the power-law exponents (D) of emphysema hole-size distributions as a competent emphysema index. Robustness to extreme breath-hold-level variations and correlations with clinical parameters for chronic obstructive pulmonary disease (COPD) were investigated and compared to a conventional emphysema index (EI%). Patients and methods: A total of 100 patients with COPD (97 males and three females of mean age 67±7.9 years) underwent multidetector row computed tomography scanning at full inspiration and full expiration. The diameters of the emphysematous holes were estimated and quantified with a fully automated algorithm. Power-law exponents (D) of emphysematous hole-size distribution were evaluated. Results: The diameters followed a power-law distribution in all cases, suggesting the scale-free nature of emphysema. D of inspiratory and expiratory computed tomography of patients showed intraclass correlation coefficients >0.8, indicating statistically absolute agreement of different breath-hold levels. By contrast, the EI% failed to agree. Bland–Altman analysis also revealed the superior robustness of D to EI%. D also significantly correlated with clinical parameters such as airflow limitation, diffusion capacity, exercise capacity, and quality of life. Conclusion: The D of emphysematous hole-size distribution is robust to breath-hold-level variations and sensitive to the severity of emphysema. This measurement may help rule out the confounding effects of variations in breath-hold levels. Keywords: chronic obstructive pulmonary disease, emphysema, computed tomography, quantitative imaging, breath-hold, power law

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A size-based emphysema severity index: robust to the breath-hold-level variations and correlated with clinical parameters

International Journal of COPD a size-based emphysema severity index: robust to the breath-hold-level variations and correlated with clinical parameters Yeon-Mok Oh 0 2 4 0 Department of Convergence Medicine 1 Department of radiology 2 Joon Beom seo 3 asan Institute for life sciences 4 Department of Pulmonary and Critical Care Medicine, University of Ulsan College of Medicine, a san Medical Center , s eoul, r epublic of Korea 8 1 0 2 - l u J - 2 1 n o 8 3 1 . 7 4 2 . 8 3 . 1 5 y b / m o c . s s e r p e v o d . w w w / / : s p t th l.y rom on f e d s de lu loa ona saedonw rrsopeF PowerdbyTCPDF(ww.tcpdf.org) O r I g I n a l r e s e a r C h Jeongeun hwang 1 Minho lee 2 sang Min lee 2 sang Young Oh 2 Objective: To determine the power-law exponents (D) of emphysema hole-size distributions as a competent emphysema index. Robustness to extreme breath-hold-level variations and correlations with clinical parameters for chronic obstructive pulmonary disease (COPD) were investigated and compared to a conventional emphysema index (EI%). Patients and methods: A total of 100 patients with COPD (97 males and three females of mean age 67±7.9 years) underwent multidetector row computed tomography scanning at full inspiration and full expiration. The diameters of the emphysematous holes were estimated and quantified with a fully automated algorithm. Power-law exponents (D) of emphysematous holesize distribution were evaluated. Results: The diameters followed a power-law distribution in all cases, suggesting the scale-free nature of emphysema. D of inspiratory and expiratory computed tomography of patients showed intraclass correlation coefficients .0.8, indicating statistically absolute agreement of different breath-hold levels. By contrast, the EI% failed to agree. Bland-Altman analysis also revealed the superior robustness of D to EI%. D also significantly correlated with clinical parameters such as airflow limitation, diffusion capacity, exercise capacity, and quality of life. Conclusion: The D of emphysematous hole-size distribution is robust to breath-hold-level variations and sensitive to the severity of emphysema. This measurement may help rule out the confounding effects of variations in breath-hold levels. chronic obstructive pulmonary disease; emphysema; computed tomography; quan- - open access to scientific and medical research *These authors contributed equally to this work Introduction Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality that imposes significant socioeconomic burden globally.1,2 Emphysema, one of the key components in the pathophysiology of COPD, is characterized by alveolar wall destruction3–6 and can be quantified using computed tomography (CT) scanning.7–9 Reliable and objective quantification of emphysema severity is a key to proper diagnosis and treatment.9–11 Increased emphysema volume fraction, expressed as percent emphysema index (EI%), on CT images in COPD patients has been reported to represent the severity of pulmonary emphysema.7–11 EI% is widely used because it is intuitive and correlates with histopathology measurements12 and scoring by radiologists.13 However, an important limitation of EI% is its susceptibility to occasional variations in breath-hold levels. Thus, EI% in patients with similar emphysema severity may differ, depending on variations in breath-hold levels during CT scanning. These variations, which may result in the over- or underestimation of emphysema severity, are especially problematic in patients with severe airflow limitation or pain while breathing. This limitation has hindered multicenter and/or longitudinal 81 studies, as irregularities in CT image acquisition may be l-u20 more frequent. -J21 The lung has a scale-free, fractal nature,14–19 with the fracon tal dimension power-law exponents (D) reflecting intrinsic .381 complexity.20 The distribution of emphysematous hole sizes .742 has been shown to follow a power law, with the exponent .83 associated with clinical parameters.20,21 Moreover, the powery15 law exponent deduced from the distribution in emphysema/bm tous hole sizes may reflect the extent of intrinsic complexity. .sco This study describes the development of a new algorithm to rspe measure the size of emphysematous holes and its applicavode tion in determining D. This exponent, D, may constitute a .ww new emphysema severity index that is robust to variations in /:/w breath-hold levels. It was hypothesized that these variations s th .y in breath-hold levels alter the size of emphysematous holes p t rom on but not the statistical properties of size distribution. The D of l fdde lseu emphysematous hole-size distribution may therefore repreloa ona sent the unaltered statistical property. To date, this hypothesis saedonw rrsopeF ahtasdinfofetrbeenetnbvreaalitdha-hteodldulseinvgelCs.T images of the same patients e s i D y r a n o m l u P e v it c u tr s b O c i n o r h C f o l a n r u o J l a n o it a n tr e n I Patients an (...truncated)


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Jeongeun Hwang, Minho Lee, Sang Min Lee, Sang Young Oh, Yeon-Mok Oh, Namkug Kim, Joon Beom Seo. A size-based emphysema severity index: robust to the breath-hold-level variations and correlated with clinical parameters, International Journal of Chronic Obstructive Pulmonary Disease, 2016, pp. 1835-1841, DOI: 10.2147/COPD.S109846