Short-term effect of changes in smoking behaviour on emphysema quantification by CT

Ashraf, Haseem; Lo, Pechin; Shaker, Saher Burhan; Bruijne, Marleen de; Dirksen, Asger; Tønnesen, Philip; Dahlbäck, Magnus; Pedersen, Jesper Holst

doi:10.1136/thx.2009.132688

Cited by 72 publications

(73 citation statements)

References 32 publications

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“…Using clinical meaningful detectable change in lung density metrics (i.e. detectable based on current scanner resolution and a reasonable sample size of few hundred subjects) from published literature(14–16) and results of our repeatability analysis, we extrapolated to the number of subjects needed to achieve at least 80% power to detect a typical change in lung density metrics over a short period of time. For the low attenuation area variables that we considered (%LAA856, %LAA910, and %LAA950), the power analyses utilized relative percent difference between repeat scans.…”

Section: Methodsmentioning

confidence: 99%

Repeatability and Sample Size Assessment Associated with Computed Tomography-Based Lung Density Metrics

Iyer¹,

Grout²,

Zamba³

et al. 2014

J COPD F

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Rationale and Objectives Density-based metrics assess severity of lung disease but vary with lung inflation and method of scanning. The aim of this study was to evaluate the repeatability of single center, CT-based density metrics of the lung in a normal population and assess study sample sizes needed to detect meaningful changes in lung density metrics when scan parameters and volumes are tightly controlled. Materials and Methods Thirty-seven subjects (normal smokers and non-smokers) gave consent to have randomly assigned repeated, breath-held scans at either inspiration (90% vital capacity: TLC) or expiration (20% vital capacity: FRC). Repeated scans were analyzed for: mean lung density (MLD), 15th percentile point of the density histogram (P15), low attenuation areas (LAA) and alpha (fractal measure of hole size distribution). Using inter-subject differences and previously reported bias, sample size was estimated from month or yearly change in density metrics obtained from published literature (i.e. meaningful change). Results Inter-scan difference measurements were small for density metrics (ICC > 0.80) and average ICCs for whole lung alpha−910 and alpha−950 were 0.57 and 0.64, respectively. Power analyses demonstrated that, under the control conditions with minimal extrinsic variation, population sizes needed to detect meaningful changes in density measures for TLC or FRC repeated scans ranged from a few (20–40) to a few hundred subjects, respectively. Conclusion A meaningful sample size was predicted from this study using volume-controlled normal subjects in a controlled imaging environment. Under proper breath-hold conditions, high repeatability was obtained in cohorts of normal smokers and non-smokers.

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Section: Methodsmentioning

confidence: 99%

Repeatability and Sample Size Assessment Associated with Computed Tomography-Based Lung Density Metrics

Iyer¹,

Grout²,

Zamba³

et al. 2014

J COPD F

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“…Age, obesity, and other factors related to ability to attain total lung capacity (50) may also have affected our measurements. Unlike spirometric measurements, percent emphysema is known to be affected acutely by cigarette smoking (42). We did not examine this relationship directly in this study, but we present separate equations for percent emphysema for use with current smokers.…”

Section: Original Researchmentioning

confidence: 99%

Variation in the Percent of Emphysema-like Lung in a Healthy, Nonsmoking Multiethnic Sample. The MESA Lung Study

Hoffman

Ahmed²,

Baumhauer³

et al. 2014

Annals ATS

104

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Rationale: Computed tomography (CT)-based lung density is used to quantitate the percentage of emphysema-like lung (hereafter referred to as percent emphysema), but information on its distribution among healthy nonsmokers is limited.Objectives: We evaluated percent emphysema and total lung volume on CT scans of healthy never-smokers in a multiethnic, population-based study. Methods:The Multi-Ethnic Study of Atherosclerosis (MESA) Lung Study investigators acquired full-lung CT scans of 3,137 participants (ages 54-93 yr) between 2010-12. The CT scans were taken at full inspiration following the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) protocol. "Healthy never-smokers" were defined as participants without a history of tobacco smoking or respiratory symptoms and disease. "Percent emphysema" was defined as the percentage of lung voxels below 2950 Hounsfield units. "Total lung volume" was defined by the volume of lung voxels.Measurements and Main Results: Among 854 healthy neversmokers, the median percent emphysema visualized on full-lung scans was 1.1% (interquartile range, 0.5-2.5%). The percent emphysema values were 1.2 percentage points higher among men compared with women and 0.7, 1.2, and 1.2 percentage points lower among African Americans, Hispanics, and Asians compared with whites, respectively (P , 0.001). Percent emphysema was positively related to age and height and inversely related to body mass index. The findings were similar for total lung volume on CT scans and for percent emphysema defined at 2910 Hounsfield units and measured on cardiac scans. Reference equations to account for these differences are presented for never, former and current smokers.Conclusions: Similar to lung function, percent emphysema varies substantially by demographic factors and body size among healthy never-smokers. The presented reference equations will assist in defining abnormal values for percent emphysema and total lung volume on CT scans, although validation is pending.

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“…40,41 Even more intriguingly, the extent of emphysema appears to increase quite rapidly following smoking cessation, reflecting a fall in lung attenuation. 42,43 This effect is presumed to be due to a smoking-induced increase in inflammatory cells in the lung in current smokers, resulting in increased lung attenuation, so that partial volume averaging masks the areas of low-attenuation emphysema. Therefore, smoking status should always be taken into account when assessing severity of emphysema by quantitative CT.…”

Section: Sources Of Variationmentioning

confidence: 99%

Progress in Imaging COPD, 2004 - 2014

Lynch¹

2014

J COPD F

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Abbreviations: computed tomography, CT; magnetic resonance imaging, MRI; positron emission tomography, PET; Global Initiative for chronic Obstructive Lung Disease, GOLD; quantitative CT, QCT; Hounsfield Units, HU; percentage of low attenuation area, %LAA; relative area of lung less than -950 HU, RA950; Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints, ECLIPSE; forced expiratory volume in 1 second, FEV1; forced vital capacity, FVC. Journal of the COPD Foundation(GOLD) stage may have substantial, little, or no emphysema. Discrete subphenotypes of COPD include emphysema of varying morphologic appearance, large airway abnormality and small airway obstruction. Increasing awareness of the heterogeneity of COPD has led to increased use of CT to characterize COPD for purposes of genetic evaluation and identification of specific subgroups which may be amenable to therapeutic trials. 1-3 While visual assessment is important in determining the presence and character of emphysema, the last decade has been characterized by increasing use of quantitative imaging to provide precise estimates of the severity and distribution of emphysema, gas trapping and airway wall thickening. Several large cohorts of cigarette smokers have now been quite extensively characterized by CT, resulting in increased knowledge of the clinical correlates of quantitative CT parameters. [4][5][6] The purpose of this paper is to present the substantial contribution that imaging has made to our understanding of COPD over the past 10 years. AbstractComputed tomography (CT) has contributed substantially to our understanding of COPD over the past decade. Visual and quantitative assessments of CT in COPD are complementary. Visual assessment should provide assessment of centrilobular, panlobular and paraseptal emphysema, airway wall thickening, bronchiectasis, findings of respiratory bronchiolitis, and enlargement of the pulmonary artery. Quantitative CT permits evaluation of severity of emphysema, airway wall thickening, and expiratory air trapping, and is now being used for longitudinal evaluation of the progression of COPD. Innovative techniques are being developed to use CT to characterize the pattern of emphysema and smoking-related respiratory bronchiolitis. Magnetic resonance imaging (MRI) and positron emission tomography PET-CT are useful research tools in the evaluation of COPD.

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Short-term effect of changes in smoking behaviour on emphysema quantification by CT

Cited by 72 publications

References 32 publications

Repeatability and Sample Size Assessment Associated with Computed Tomography-Based Lung Density Metrics

Repeatability and Sample Size Assessment Associated with Computed Tomography-Based Lung Density Metrics

Variation in the Percent of Emphysema-like Lung in a Healthy, Nonsmoking Multiethnic Sample. The MESA Lung Study

Progress in Imaging COPD, 2004 - 2014

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