Variation in quantitative CT air trapping in heavy smokers on repeat CT examinations.
ABSTRACT OBJECTIVES: To determine the variation in quantitative computed tomography (CT) measures of air trapping in low-dose chest CTs of heavy smokers. METHODS: We analysed 45 subjects from a lung cancer screening trial, examined by CT twice within 3 months. Inspiratory and expiratory low-dose CT was obtained using breath hold instructions. CT air trapping was defined as the percentage of voxels in expiratory CT with an attenuation below -856 HU (EXP(-856)) and the expiratory to inspiratory ratio of mean lung density (E/I-ratio(MLD)). Variation was determined using limits of agreement, defined as 1.96 times the standard deviation of the mean difference. The effect of both lung volume correction and breath hold reproducibility was determined. RESULTS: The limits of agreement for uncorrected CT air trapping measurements were -15.0 to 11.7 % (EXP(-856)) and -9.8 to 8.0 % (E/I-ratio(MLD)). Good breath hold reproducibility significantly narrowed the limits for EXP(-856) (-10.7 to 7.5 %, P = 0.002), but not for E/I-ratio(MLD) (-9.2 to 7.9 %, P = 0.75). Statistical lung volume correction did not improve the limits for EXP(-856) (-12.5 to 8.8 %, P = 0.12) and E/I-ratio(MLD) (-7.5 to 5.8 %, P = 0.17). CONCLUSIONS: Quantitative air trapping measures on low-dose CT of heavy smokers show considerable variation on repeat CT examinations, regardless of lung volume correction or reproducible breath holds. KEY POINTS: • Computed tomography quantitatively measures small airways disease in heavy smokers. • Measurements of air trapping vary considerably on repeat CT examinations. • Variation remains substantial even with reproducible breath holds and lung volume correction.
Article: Relationship between peripheral airway dysfunction, airway obstruction, and neutrophilic inflammation in COPD.[show abstract] [hide abstract]
ABSTRACT: Considerable research has been conducted into the nature of airway inflammation in chronic obstructive pulmonary disease (COPD) but the relationship between proximal airways inflammation and both dynamic collapse of the peripheral airways and HRCT determined emphysema severity remains unknown. A number of research tools have been combined to study smokers with a range of COPD severities classified according to the GOLD criteria. Sixty five subjects (11 healthy smokers, 44 smokers with stage 0-IV COPD, and 10 healthy non-smokers) were assessed using lung function testing and HRCT scanning to quantify emphysema and peripheral airway dysfunction and sputum induction to measure airway inflammation. Expiratory HRCT measurements and the expiratory/inspiratory mean lung density ratio (both indicators of peripheral airway dysfunction) correlated more closely in smokers with the severity of airflow obstruction (r = -0.64, p<0.001) than did inspiratory HRCT measurements (which reflect emphysema severity; r = -0.45, p<0.01). Raised sputum neutrophil counts also correlated strongly in smokers with HRCT indicators of peripheral airway dysfunction (r = 0.55, p<0.001) but did not correlate with HRCT indicators of the severity of emphysema. This study suggests that peripheral airway dysfunction, assessed by expiratory HRCT measurements, is a determinant of COPD severity. Airway neutrophilia, a central feature of COPD, is closely associated with the severity of peripheral airway dysfunction in COPD but is not related to the overall severity of emphysema as measured by HRCT.Thorax 10/2004; 59(10):837-42. · 6.84 Impact Factor
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ABSTRACT: The aggressive and heterogeneous nature of lung cancer has thwarted efforts to reduce mortality from this cancer through the use of screening. The advent of low-dose helical computed tomography (CT) altered the landscape of lung-cancer screening, with studies indicating that low-dose CT detects many tumors at early stages. The National Lung Screening Trial (NLST) was conducted to determine whether screening with low-dose CT could reduce mortality from lung cancer. From August 2002 through April 2004, we enrolled 53,454 persons at high risk for lung cancer at 33 U.S. medical centers. Participants were randomly assigned to undergo three annual screenings with either low-dose CT (26,722 participants) or single-view posteroanterior chest radiography (26,732). Data were collected on cases of lung cancer and deaths from lung cancer that occurred through December 31, 2009. The rate of adherence to screening was more than 90%. The rate of positive screening tests was 24.2% with low-dose CT and 6.9% with radiography over all three rounds. A total of 96.4% of the positive screening results in the low-dose CT group and 94.5% in the radiography group were false positive results. The incidence of lung cancer was 645 cases per 100,000 person-years (1060 cancers) in the low-dose CT group, as compared with 572 cases per 100,000 person-years (941 cancers) in the radiography group (rate ratio, 1.13; 95% confidence interval [CI], 1.03 to 1.23). There were 247 deaths from lung cancer per 100,000 person-years in the low-dose CT group and 309 deaths per 100,000 person-years in the radiography group, representing a relative reduction in mortality from lung cancer with low-dose CT screening of 20.0% (95% CI, 6.8 to 26.7; P=0.004). The rate of death from any cause was reduced in the low-dose CT group, as compared with the radiography group, by 6.7% (95% CI, 1.2 to 13.6; P=0.02). Screening with the use of low-dose CT reduces mortality from lung cancer. (Funded by the National Cancer Institute; National Lung Screening Trial ClinicalTrials.gov number, NCT00047385.).New England Journal of Medicine 08/2011; 365(5):395-409. · 53.30 Impact Factor