Air Trapping at CT: High Prevalence in Asymptomatic Subjects with Normal Pulmonary Function

Tanaka, Nobuyuki; Matsumoto, Tsuneo; Miura, Gouji; Emoto, Takuya; Matsunaga, Naofumi; Ueda, Katsuhiko; Lynch, David A.

doi:10.1148/radiol.2273020352

Cited by 113 publications

(71 citation statements)

References 22 publications

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“…with minimal (<10%) air trapping, which may have yielded better within-subject repeatability. Several studies have reported similar ranges in air-trapping percentages in asymptomatic smokers, as high as 20%(6). We used FRC scans to measure air trapping rather than full expiratory scans because of subject difficulty in holding their breath at RV and because of know correlations, at FRC, between air-trapping and clinical metrics of lung disease(17, 18).…”

Section: Discussionmentioning

confidence: 81%

“…Lung density measurements based upon the density histogram have been useful to quantify the presence and distribution of air trapping and emphysema-like lung regions in COPD and asthma patients, but the pattern and percentage can vary even among normal subjects(6). Subject differences in inspiratory and expiratory effort, scanner type, radiation dose, and reconstruction algorithms have considerable effect on quantification of regional parenchymal pathology and their association with global measures of lung function(7–10).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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: Discussionmentioning

confidence: 81%

Section: Introductionmentioning

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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“…Although such ''gas trapping'' is apparent even in asymptomatic individuals who have normal lung function [86], it is markedly increased in patients with asthma and the degree of gas trapping is related to abnormalities of lung function [33,34,48,70,87].…”

Section: Gas Trappingmentioning

confidence: 99%

Computed tomographic imaging of the airways: relationship to structure and function

Jong

Müller²,

Paré³

et al. 2005

European Respiratory Journal

156

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Alterations in the structure of the airways, collectively termed airway remodelling, contribute to airflow obstruction in a variety of chronic lung diseases. While histology has provided valuable insights into the structure of airway wall remodelling, this technique is invasive and does not allow the longitudinal analysis of airway wall dimensions. Technical advances in computed tomography allow the assessment of airway wall dimensions, and are ideally suited for the noninvasive investigation of the pathogenesis of airway wall remodelling and the evaluation of new therapeutic interventions. The aim of this article is to review the use of computed tomography in the investigation of airway structure and function in health and disease.

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“…Regional air trapping was only scored as absent or present (three or more secondary lobules involved) while several studies have shown that some air trapping can also be seen in nonobstructive smokers, as in healthy volunteers [17][18][19]. This is also reflected in the high and similar prevalence rates of regional air trapping in nonobstructive smokers and healthy volunteers in their study.…”

mentioning

confidence: 83%

Air trapping on computed tomography: regional versus diffuse

Hoesein

Jong

2017

Eur Respir J

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Chronic obstructive pulmonary disease (COPD) is diagnosed and classified by spirometry, assessing the presence of airflow obstruction and extent of forced expiratory flow deterioration. Spirometry, however, is unsuitable for characterising and quantifying the underlying pulmonary pathology of COPD, including alveolar destruction (emphysema) and airway remodelling (large-and small-airway disease). Accurate diagnosis of the pulmonary pathologies underlying COPD is seen as an important step towards better understanding its biology and "personalised" treatment. Computed tomography (CT) of the lungs provides an excellent opportunity to assess COPD in vivo and quantify its macroscopic pathology [1][2][3]. Emphysema and airway remodelling can be visually assessed and automatically quantified, and several studies have shown associations with morbidity and mortality [4][5][6][7]. In addition, CT can provide information on the spatial distribution of disease.In this issue of the European Respiratory Journal, KARIMI et al. [8] hypothesise that regional air trapping maybe a new imaging marker, in addition to emphysema, large-airway remodelling and diffuse air trapping.The small airways, commonly defined as those <2 mm in diameter, are regarded as the most important site of airflow obstruction in COPD [9]. Measuring small-airway disease on CT can be challenging as these cannot be visualised directly because they are too small and below the resolution of the CT scanner. Indirect measures are thus used to measure small-airway disease on CT. Air trapping on CT, sometimes also referred to as gas trapping, is often used to asses small-airway disease [10]. Pathophysiologically, it is defined as retention of air in the lung distal to an obstruction, but it is difficult to prove this by radiology-pathology correlation studies. To assess air trapping, both inspiratory and some form of expiratory scans are needed.The definition of regional air trapping on CT consists of three components. First, the trapped areas have a relatively high attenuation on expiratory CT scans. Fully inflated alveoli have an average attenuation of −850 Hounsfield units (HU) and with a good expiratory effort, the average attenuation increases by 150 HU. The second component is volume, as areas with air trapping do not lose much of their volume on expiration. The third component is morphology, as air trapping has a sharp delineation at the border of the secondary pulmonary lobule.The radiological diagnosis of regional air trapping is challenging for several reasons. First, proper expiration is needed for the air trapping to become visible. This needs compliance from patients or research participants, properly trained technicians, and/or spirometric gating. CT technicians tend to train patients to only a limited extent before the CT acquisition and they also sometimes start the scan too

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Air Trapping at CT: High Prevalence in Asymptomatic Subjects with Normal Pulmonary Function

Abstract: Various degrees of air trapping, including the mosaic or extensive types, can be observed in subjects with normal pulmonary function and have no correlation with the subject's current smoking status or cigarette consumption.

Cited by 113 publications

References 22 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

Computed tomographic imaging of the airways: relationship to structure and function

Air trapping on computed tomography: regional versus diffuse

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