CT-Definable Subtypes of Chronic Obstructive Pulmonary Disease: A Statement of the Fleischner Society

Development of a pulmonary imaging biomarker pipeline for phenotyping of chronic lung disease

We designed and generated pulmonary imaging biomarker pipelines to facilitate high-throughput research and point-of-care use in patients with chronic lung disease. Image processing modules and algorithm pipelines were embedded within a graphical user interface (based on the .NET framework) for pulmonary magnetic resonance imaging (MRI) and x-ray computed-tomography (CT) datasets. The software pipelines were generated using C++ and included: (1) inhaled He3/Xe129 MRI ventilation and apparent diffusion coefficients, (2) CT-MRI coregistration for lobar and segmental ventilation and perfusion measurements, (3) ultrashort echo-time H1 MRI proton density measurements, (4) free-breathing Fourier-decomposition H1 MRI ventilation/perfusion and free-breathing H1 MRI specific ventilation, (5) multivolume CT and MRI parametric response maps, and (6) MRI and CT texture analysis and radiomics. The image analysis framework was implemented on a desktop workstation/tablet to generate biomarkers of regional lung structure and function related to ventilation, perfusion, lung tissue texture, and integrity as well as multiparametric measures of gas trapping and airspace enlargement. All biomarkers were generated within 10 min with measurement reproducibility consistent with clinical and research requirements. The resultant pulmonary imaging biomarker pipeline provides real-time and automated lung imaging measurements for point-of-care and high-throughput research.

Quantification of pleural plaques by computed tomography and correlations with pulmonary function: preliminary study

Background

The aims of this study were to quantify pleural plaque volumes (PPVs) by computed tomography (CT) and investigate relations between PPV and pulmonary function after excluding other factors that might affect pulmonary function.

Methods

Twenty-six subjects with pleural plaques and pulmonary function test (PFT) results among 1,544 subjects that registered with the Korea Environment Corporation for asbestos damage relief from January 2011 to December 2015 were included. Subjects with CT evidence of lung diseases and/or previous surgery were excluded. PPVs were measured by tracing the outlines of all pleural plaques on CT images. Patients were allocated to three groups by PPV, as follows, <10, 10-20, or ≥20 mL, and the PFT results of these groups were analyzed and compared. Simple linear regression analysis and multiple regression analysis were used to evaluate correlations between PPV and PFT variables.

Results

No significant relationship was found between total PPV and pulmonary function indices or between PPV groups and PFT results (P>0.05). However, forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), and diffusing capacity of the lung for carbon monoxide (DLCO) values in the higher PPV group (≥20 mL) tended to be lower, indicating a restrictive pattern of pulmonary function.

Conclusions

We quantified PPV on CT and found out higher PPV tended to exhibit a restrictive pattern. However, pleural plaques alone were not found to be significantly associated with pulmonary function.

CT-based Visual Classification of Emphysema: Association with Mortality in the COPDGene Study

Purpose

To determine whether visually assessed patterns of emphysema at CT might provide a simple assessment of mortality risk among cigarette smokers.

Materials and Methods

Of the first 4000 cigarette smokers consecutively enrolled between 2007 and 2011 in this COPDGene study, 3171 had data available for both visual emphysema CT scores and survival. Each CT scan was retrospectively visually scored by two analysts using the Fleischner Society classification system. Severity of emphysema was also evaluated quantitatively by using percentage lung volume occupied by low-attenuation areas (voxels with attenuation of −950 HU or less) (LAA-950). Median duration of follow-up was 7.4 years. Regression analysis for the relationship between imaging patterns and survival was based on the Cox proportional hazards model, with adjustment for age, race, sex, height, weight, pack-years of cigarette smoking, current smoking status, educational level, LAA-950, and (in a second model) forced expiratory volume in 1 second (FEV₁).

Results

Observer agreement in visual scoring was good (weighted κ values, 0.71–0.80). There were 519 deaths in the study cohort. Compared with subjects who did not have visible emphysema, mortality was greater in those with any grade of emphysema beyond trace (adjusted hazard ratios, 1.7, 2.5, 5.0, and 4.1, respectively, for mild centrilobular emphysema, moderate centrilobular emphysema, confluent emphysema, and advanced destructive emphysema, P < .001). This increased mortality generally persisted after adjusting for LAA-950.

Conclusion

The visual presence and severity of emphysema is associated with significantly increased mortality risk, independent of the quantitative severity of emphysema.

Online supplemental material is available for this article.

Finding the right spot: Where to measure airway parameters in patients with COPD

PURPOSE

The importance of spirometry for management of COPD was reduced in the 2017 revision of the GOLD report. CT derived airway measurements show strong correlations with lung function tests and symptoms. However, these correlations are specific to the airway localization, and currently there is no evidence for the ideal spot. Therefore, the aim of this prospective study was to systematically correlate CT derived airway measurements with extensive lung function testing.

METHODS AND MATERIALS

65 patients with diagnosed COPD underwent body plethysmography, impulse oscillometry and dose optimized qCT examination (Somatom Force, Healthineers, Germany) in inspiration and expiration. Eight airway parameters (e.g. outer diameter, maximal wall thickness) were acquired for both scans in every lobe for the third to fifth generation bronchus and correlated with the lung function tests.

RESULTS

The most significant correlations between airway parameters were found for the third generation bronchus of the upper left lobe during expiration (25 out of 48 correlation pairs, mean r = -0.39) and for the third generation bronchus of the upper right lobe during inspiration (9 out of 48 correlation pairs, mean r = -0.25). No significant correlations were for example found for the upper right lobe in expiration.

CONCLUSION

Correlations between airway parameters and lung function tests vary widely between lobes, bronchus generations and breathing states. Our work suggests that the third generation bronchus of the upper left lobe in expiration could be the preferred localization for airway quantification in future studies.

Ultra-low-dose lung screening CT with model-based iterative reconstruction: an assessment of image quality and lesion conspicuity

Background Reducing radiation dose inevitably increases image noise, and thus, it is important in low-dose computed tomography (CT) to maintain image quality and lesion detection performance. Purpose To assess image quality and lesion conspicuity of ultra-low-dose CT with model-based iterative reconstruction (MBIR) and to determine a suitable protocol for lung screening CT. Material and Methods A total of 120 heavy smokers underwent lung screening CT and were randomly and equally assigned to one of five groups: group 1 = 120 kVp, 25 mAs, with FBP reconstruction; group 2 = 120 kVp, 10 mAs, with MBIR; group 3 = 100 kVp, 15 mAs, with MBIR; group 4 = 100 kVp, 10 mAs, with MBIR; and group 5 = 100 kVp, 5 mAs, with MBIR. Two radiologists evaluated intergroup differences with respect to radiation dose, image noise, image quality, and lesion conspicuity using the Kruskal-Wallis test and the Chi-square test. Results Effective doses were 61-87% lower in groups 2-5 than in group 1. Image noises in groups 1 and 5 were significantly higher than in the other groups ( P < 0.001). Overall image quality was best in group 1, but diagnostic acceptability of overall image qualities in groups 1-3 was not significantly different (all P values > 0.05). Lesion conspicuities were similar in groups 1-4, but were significantly poorer in group 5. Conclusion Lung screening CT with MBIR obtained at 100 kVp and 15 mAs enables a ∼60% reduction in radiation dose versus low-dose CT, while maintaining image quality and lesion conspicuity.

Effect of Liuweibuqi capsules on CD4+CD25+Foxp3+ regulatory T cells, helper T cells and lung function in patients with stable chronic obstructive pulmonary disease complicated with lung Qi deficiency

Background

Chronic obstructive pulmonary disease (COPD) is predicted to become the fifth leading cause of disability and the third leading cause of death around the world by 2020. Though it is potentially treatable and preventable, evidence of brain structural alterations in COPD remains sparse and conflicting. We aim to investigate the effect of Liuweibuqi capsules on CD4⁺CD25⁺ Forkhead box protein 3⁺ (Foxp3⁺) regulatory T cells (Tregs), helper T cells (Th) and lung function in patients with stable COPD complicated with lung Qi deficiency.

Methods

COPD patients with lung Qi deficiency [458] were assigned into non-smoking COPD (NS-COPD), non-smoking control (NS-control), smoking COPD (S-COPD) and smoking control (S-control) groups, and healthy volunteers [245] into the non-smoking healthy (NSH) and smoking healthy (SH) groups. Levels of inflammatory cytokines were detected by Enzyme-linked immunoassay (ELISA). Contents of inflammatory cells, inflammatory marker, and CD4⁺CD25⁺Fox3⁺Tregs were measured by flow cytometry. FEV1/FVC (%) and FEV1 (%) were detected by pulmonary function test apparatus. Correlation between FEV1 (%) and Th1, Th2, Th17, Th1/Th2 or CD4⁺CD25⁺Fox3⁺Tregs was analyzed by Spearman rank correlation test. The related factors affecting treatment efficacy was assessed by logistic analysis.

Results

COPD patients and smoking people showed higher level of INF-γ, IL-4, IL-17, Th1, Th2, Th17 and Th1/Th2 but lower level of CD4⁺CD25⁺Fox3⁺Tregs. Liuweibuqi capsules could decrease level of inflammatory cells, cytokines, and markers (especially Th17 and IL-17), and increase level of CD4⁺CD25⁺Fox3⁺Tregs. FEV1 (%) negatively correlated with Th1, Th2, Th17 and Th1/Th2 but positively correlated with CD4⁺CD25⁺Fox3⁺Tregs, and smoking may strengthen their correlation, but Liuweibuqi capsules may weaker their correlation. Levels of inflammatory cytokines, cells, marker, CD4⁺CD25⁺Fox3⁺Tregs, FEV1/FVC (%), FEV1 (%), smoking and Liuweibuqi capsules are factors affecting efficacy.

Conclusions

Taken together, our data support the notion that smoking is an important factor to induce and aggravate COPD. Liuweibuqi capsules could stimulate proliferation of CD4⁺CD25⁺Fox3⁺Tregs and decrease Th17 expression to improve the lung function in stable COPD patients with lung Qi deficiency, and it had obvious efficacy for smoking COPD patients.

Cigarette Smoke-Induced Acquired Dysfunction of Cystic Fibrosis Transmembrane Conductance Regulator in the Pathogenesis of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a disease state characterized by airflow limitation that is not fully reversible. Cigarette smoke and oxidative stress are main etiological risks in COPD. Interestingly, recent studies suggest a considerable overlap between chronic bronchitis (CB) phenotypic COPD and cystic fibrosis (CF), a common fatal hereditary lung disease caused by genetic mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Phenotypically, CF and COPD are associated with an impaired mucociliary clearance and mucus hypersecretion, although they are two distinct entities of unrelated origin. Mechanistically, the cigarette smoke-increased oxidative stress-induced CFTR dysfunction is implicated in COPD. This underscores CFTR in understanding and improving therapies for COPD by altering CFTR function with antioxidant agents and CFTR modulators as a great promising strategy for COPD treatments. Indeed, treatments that restore CFTR function, including mucolytic therapy, antioxidant ROS scavenger, CFTR stimulator (roflumilast), and CFTR potentiator (ivacaftor), have been tested in COPD. This review article is aimed at summarizing the molecular, cellular, and clinical evidence of oxidative stress, particularly the cigarette smoke-increased oxidative stress-impaired CFTR function, as well as signaling pathways of CFTR involved in the pathogenesis of COPD, with a highlight on the therapeutic potential of targeting CFTR for COPD treatment.

HU deviation in lung and bone tissues: Characterization and a corrective strategy

INTRODUCTION

In the era of precision medicine, quantitative applications of x-ray Computed Tomography (CT) are on the rise. These require accurate measurement of the CT number, also known as the Hounsfield Unit. In this study, we evaluated the effect of patient attenuation-induced beam hardening of the x-ray spectrum on the accuracy of the HU values and a strategy to correct for the resulting deviations in the measured HU values.

MATERIALS AND METHODS

A CIRS electron density phantom was scanned on a Siemens Biograph mCT Flow CT scanner and a GE Discovery 710 CT scanner using standard techniques that are employed in the clinic to assess the HU deviation caused by beam hardening in different tissue types. In addition, an anthropomorphic ATOM adult male upper torso phantom was scanned on the GE Discovery 710 scanner. Various amounts of Superflab bolus material were wrapped around the phantoms to simulate different patient sizes. The mean HU values that were measured in the phantoms were evaluated as a function of the water-equivalent area (A_w ), a parameter that is described in the report of AAPM Task Group 220. A strategy by which to correct the HU values was developed and tested. The variation in the HU values in the anthropomorphic ATOM phantom under different simulated body sizes, both before and after correction, were compared, with a focus on the lung and bone tissues.

RESULTS

Significant HU deviations that depended on the simulated patient size were observed. A positive correlation between HU and A_w was observed for tissue types that have an HU of less than zero, while a negative correlation was observed for tissue types with HU values that are greater than zero. The magnitude of the difference increases as the underlying attenuation property deviates further away from that of water. In the electron density phantom study, the maximum observed HU differences between the measured and reference values in the cortical bone and lung materials were 426 and 94 HU, respectively. In the anthropomorphic phantom study, the HU difference was as much as -136.7 ± 8.2 HU (or -7.6% ± 0.5% of the attenuation coefficient, AC) in the spine region, and up to 37.6 ± 1.6 HU (or 17.3% ± 0.8% of AC) in the lung region between scenarios that simulated normal and obese patients. Our HU correction method reduced the HU deviations to 8.5 ± 9.1 HU (or 0.5% ± 0.5%) for bone and to -6.4 ± 1.7 HU (or -3.0% ± 0.8%) for lung. The HU differences in the soft tissue materials before and after the correction were insignificant. Visual improvement of the tissue contrast was also achieved in the data of the simulated obese patient.

CONCLUSIONS

The effect of a patient's size on the HU values of lung and bone tissues can be significant. The accuracy of those HU values was substantially improved by the correction method that was developed for and employed in this study.

Time to Exhale: Additional Value of Expiratory Chest CT in Chronic Obstructive Pulmonary Disease

Objectives

Diagnostic guidelines for chronic obstructive pulmonary disease (COPD) are based on spirometry and clinical criteria. However, this does not address the pathophysiological complexity of the disease sufficiently. Until now, inspiratory chest computed tomography (CT) has been considered as the preferred imaging method in these patients. We hypothesized that expiratory CT may be superior to demonstrate pathophysiological changes. The aim of this prospective study was to systematically compare lung function tests with quantified CT parameters in inspiration and expiration.

Materials and Methods

Forty-six patients with diagnosed COPD underwent spirometry, body plethysmography, and dose-optimized CT in maximal inspiration and expiration. Four quantified CT parameters were acquired in inspiration, expiration, and their calculated delta values. These parameters were correlated with seven established lung function parameters.

Results

For inspiratory scans, a weak-to-moderate correlation with the lung function parameters was found. These correlations significantly improved when adding the expiratory scan (p < 0.05). Moreover, some parameters showed a significant correlation only in expiratory datasets. Calculated delta values showed even stronger correlation with lung function testing.

Conclusions

Expiratory quantified CT and calculated delta values significantly improve the correlation with lung function parameters. Thus, an additional expiratory CT may improve image-based phenotyping of patients with COPD.

Features of COPD as Predictors of Lung Cancer

BACKGROUND

Lung cancer is a leading cause of death and hospitalization for patients with COPD. A detailed understanding of which clinical features of COPD increase risk is needed.

METHODS

We performed a nested case-control study of Genetic Epidemiology of COPD (COPDGene) Study subjects with and without lung cancer, age 45 to 80 years, who smoked at least 10-pack years to identify clinical and imaging features of smokers, with and without COPD, that are associated with an increased risk of lung cancer. The baseline evaluation included spirometry, high-resolution chest CT scanning, and respiratory questionnaires. New lung cancer diagnoses were identified over 8 years of longitudinal follow-up. Cases of lung cancer were matched 1:4 with control subjects for age, race, sex, and smoking history. Multiple logistic regression analyses were used to determine features predictive of lung cancer.

RESULTS

Features associated with a future risk of lung cancer included decreased FEV₁/FVC (OR, 1.28 per 10% decrease [95% CI, 1.12-1.46]), visual severity of emphysema (OR, 2.31, none-trace vs mild-advanced [95% CI, 1.41-3.86]), and respiratory exacerbations prior to study entry (OR, 1.39 per increased events [0, 1, and ≥ 2] [95% CI, 1.04-1.85]). Respiratory exacerbations were also associated with small-cell lung cancer histology (OR, 3.57 [95% CI, 1.47-10]).

CONCLUSIONS

The degree of COPD severity, including airflow obstruction, visual emphysema, and respiratory exacerbations, was independently predictive of lung cancer. These risk factors should be further studied as inclusion and exclusion criteria for the survival benefit of lung cancer screening. Studies are needed to determine if reduction in respiratory exacerbations among smokers can reduce the risk of lung cancer.

Pulmonary quantitative CT imaging in focal and diffuse disease: current research and clinical applications

The frenetic development of imaging technology-both hardware and software-provides exceptional potential for investigation of the lung. In the last two decades, CT was exploited for detailed characterization of pulmonary structures and description of respiratory disease. The introduction of volumetric acquisition allowed increasingly sophisticated analysis of CT data by means of computerized algorithm, namely quantitative CT (QCT). Hundreds of thousands of CTs have been analysed for characterization of focal and diffuse disease of the lung. Several QCT metrics were developed and tested against clinical, functional and prognostic descriptors. Computer-aided detection of nodules, textural analysis of focal lesions, densitometric analysis and airway segmentation in obstructive pulmonary disease and textural analysis in interstitial lung disease are the major chapters of this discipline. The validation of QCT metrics for specific clinical and investigational needs prompted the translation of such metrics from research field to patient care. The present review summarizes the state of the art of QCT in both focal and diffuse lung disease, including a dedicated discussion about application of QCT metrics as parameters for clinical care and outcomes in clinical trials.

Quantitative computed tomography applied to interstitial lung diseases

OBJECTIVES

To evaluate a new image marker that retrieves information from computed tomography (CT) density histograms, with respect to classification properties between different lung parenchyma groups. Furthermore, to conduct a comparison of the new image marker with conventional markers.

MATERIALS AND METHODS

Density histograms from 220 different subjects (normal = 71; emphysema = 73; fibrotic = 76) were used to compare the conventionally applied emphysema index (EI), 15^th percentile value (PV), mean value (MV), variance (V), skewness (S), kurtosis (K), with a new histogram's functional shape (HFS) method. Multinomial logistic regression (MLR) analyses was performed to calculate predictions of different lung parenchyma group membership using the individual methods, as well as combinations thereof, as covariates. Overall correct assigned subjects (OCA), sensitivity (sens), specificity (spec), and Nagelkerke's pseudo R² (NR²) effect size were estimated. NR² was used to set up a ranking list of the different methods.

RESULTS

MLR indicates the highest classification power (OCA of 92%; sens 0.95; spec 0.89; NR² 0.95) when all histogram analyses methods were applied together in the MLR. Highest classification power among individually applied methods was found using the HFS concept (OCA 86%; sens 0.93; spec 0.79; NR² 0.80). Conventional methods achieved lower classification potential on their own: EI (OCA 69%; sens 0.95; spec 0.26; NR² 0.52); PV (OCA 69%; sens 0.90; spec 0.37; NR² 0.57); MV (OCA 65%; sens 0.71; spec 0.58; NR² 0.61); V (OCA 66%; sens 0.72; spec 0.53; NR² 0.66); S (OCA 65%; sens 0.88; spec 0.26; NR² 0.55); and K (OCA 63%; sens 0.90; spec 0.16; NR² 0.48).

CONCLUSION

The HFS method, which was so far applied to a CT bone density curve analysis, is also a remarkable information extraction tool for lung density histograms. Presumably, being a principle mathematical approach, the HFS method can extract valuable health related information also from histograms from complete different areas.

Emphysematous and Nonemphysematous Gas Trapping in Chronic Obstructive Pulmonary Disease: Quantitative CT Findings and Pulmonary Function

Purpose To identify a prevalent computed tomography (CT) subtype in patients with chronic obstructive pulmonary disease (COPD) by separating emphysematous from nonemphysematous contributions to total gas trapping and to attempt to predict and grade the emphysematous gas trapping by using clinical and functional data. Materials and Methods Two-hundred and two consecutive eligible patients (159 men and 43 women; mean age, 70 years [age range, 41-85 years]) were prospectively studied. Pulmonary function and CT data were acquired by pulmonologists and radiologists. Noncontrast agent-enhanced thoracic CT scans were acquired at full inspiration and expiration, and were quantitatively analyzed by using two software programs. CT parameters were set as follows: 120 kVp; 200 mAs; rotation time, 0.5 second; pitch, 1.1; section thickness, 0.75 mm; and reconstruction kernels, b31f and b70f. Gas trapping obtained by difference of inspiratory and expiratory CT density thresholds (percentage area with CT attenuation values less than -950 HU at inspiration and percentage area with CT attenuation values less than -856 HU at expiration) was compared with that obtained by coregistration analysis. A logistic regression model on the basis of anthropometric and functional data was cross-validated and trained to classify patients with COPD according to the relative contribution of emphysema to total gas trapping, as assessed at CT. Results Gas trapping obtained by difference of inspiratory and expiratory CT density thresholds was highly correlated (r = 0.99) with that obtained by coregistration analysis. Four groups of patients were distinguished according to the prevalent CT subtype: prevalent emphysematous gas trapping, prevalent functional gas trapping, mixed severe, and mixed mild. The predictive model included predicted forced expiratory volume in 1 second/vital capacity, percentage of predicted forced expiratory volume in 1 second, percentage of diffusing capacity for carbon monoxide, and body mass index as emphysema regressors at CT, with 81% overall accuracy in classifying patients according to its extent. Conclusion The relative contribution of emphysematous and nonemphysematous gas trapping obtained by coregistration of inspiratory and expiratory CT scanning can be determined accurately by difference of CT inspiratory and expiratory density thresholds. CT extent of emphysema can be predicted with accuracy suitable for clinical purposes by pulmonary function data and body mass index. ^© RSNA, 2018 Online supplemental material is available for this article.

Visual Assessment of Chest Computed Tomographic Images Is Independently Useful for Genetic Association Analysis in Studies of Chronic Obstructive Pulmonary Disease

RATIONALE

Automated analysis of computed tomographic (CT) lung images for epidemiologic and genetic association studies is increasingly common, but little is known about the utility of visual versus semiautomated emphysema and airway assessments for genetic association studies.

OBJECTIVES

Assess the relative utility of visual versus semiautomated emphysema and airway assessments for genetic association studies.

METHODS

A standardized inspection protocol was used to visually assess chest CT images for 1,540 non-Hispanic white subjects within the COPDGene Study for the presence and severity of radiographic features representing airway wall thickness and emphysema. A genome-wide association study (GWAS) was performed, and two sets of candidate single-nucleotide polymorphisms with a higher prior likelihood of association were specified a priori for separate analysis. For each visual CT examination feature, a corresponding semiautomated CT feature(s) was identified for comparison in the same subjects.

MEASUREMENTS AND MAIN RESULTS

GWAS for visual features of chest CT scans identified a genome-wide significant association with visual emphysema at the 15q25 locus (P = 6.3e^-9). In the a priori-specified set of 19 previously identified GWAS loci, 7 and 8 loci were associated with airway measures or emphysema measures, respectively. In the a priori-specified candidate gene set, 13 of 196 candidate genes harbored a nearby single-nucleotide polymorphism significantly associated with an emphysema phenotype. Visual CT examination associations were robust to adjustment for semiautomated correlates in many cases.

CONCLUSIONS

Standardized visual assessments of emphysema and airway disease are significantly associated with genetic loci previously associated with chronic obstructive pulmonary disease susceptibility or semiautomated CT examination phenotypes in GWAS. Visual CT measures of emphysema and airways disease offer independent information for genetic association studies in relation to standard semiautomated measures.

Signs of Gas Trapping in Normal Lung Density Regions in Smokers

RATIONALE

A substantial proportion of subjects without overt airflow obstruction have significant respiratory morbidity and structural abnormalities as visualized by computed tomography. Whether regions of the lung that appear normal using traditional computed tomography criteria have mild disease is not known.

OBJECTIVES

To identify subthreshold structural disease in normal-appearing lung regions in smokers.

METHODS

We analyzed 8,034 subjects with complete inspiratory and expiratory computed tomographic data participating in the COPDGene Study, including 103 lifetime nonsmokers. The ratio of the mean lung density at end expiration (E) to end inspiration (I) was calculated in lung regions with normal density (ND) by traditional thresholds for mild emphysema (-910 Hounsfield units) and gas trapping (-856 Hounsfield units) to derive the ND-E/I ratio. Multivariable regression analysis was used to measure the associations between ND-E/I, lung function, and respiratory morbidity.

MEASUREMENTS AND MAIN RESULTS

The ND-E/I ratio was greater in smokers than in nonsmokers, and it progressively increased from mild to severe chronic obstructive pulmonary disease severity. A proportion of 26.3% of smokers without airflow obstruction had ND-E/I greater than the 90th percentile of normal. ND-E/I was independently associated with FEV₁ (adjusted β = -0.020; 95% confidence interval [CI], -0.032 to -0.007; P = 0.001), St. George's Respiratory Questionnaire scores (adjusted β = 0.952; 95% CI, 0.529 to 1.374; P < 0.001), 6-minute-walk distance (adjusted β = -10.412; 95% CI, -12.267 to -8.556; P < 0.001), and body mass index, airflow obstruction, dyspnea, and exercise capacity index (adjusted β = 0.169; 95% CI, 0.148 to 0.190; P < 0.001), and also with FEV₁ change at follow-up (adjusted β = -3.013; 95% CI, -4.478 to -1.548; P = 0.001).

CONCLUSIONS

Subthreshold gas trapping representing mild small airway disease is prevalent in normal-appearing lung regions in smokers without airflow obstruction, and it is associated with respiratory morbidity. Clinical trial registered with www.clinicaltrials.gov (NCT00608764).

Occupational exposure to vapor, gas, dust, or fumes and chronic airflow limitation, COPD, and emphysema: the Swedish CArdioPulmonary BioImage Study (SCAPIS pilot)

Background

The aim of this study was to estimate the occupational burden of airflow limitation, chronic airflow limitation, COPD, and emphysema.

Materials and methods

Subjects aged 50-64 years (n=1,050) were investigated with forced expiratory volume in 1 s (FEV₁) and forced vital capacity (FVC). Airflow limitation was defined as FEV₁/FVC <0.7 before bronchodilation. Chronic airflow limitation was defined after bronchodilation either according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) as FEV₁/FVC <0.7 or according to the lower limit of normal (LLN) approach as FEV₁/FVC < LLN. COPD was defined as chronic airflow limitation (GOLD) in combination with dyspnea, wheezing, or chronic bronchitis. Emphysema was classified according to findings from computed tomography of the lungs. Occupational exposure was defined as self-reported occupational exposure to vapor, gas, dust, or fumes (VGDF). Odds ratios (OR) were calculated in models adjusted for age, gender, and smoking; population-attributable fractions and 95% CI were also calculated.

Results

There were significant associations between occupational exposure to VGDF and COPD (OR 2.7, 95% CI 1.4-51), airflow limitation (OR 1.8, 95% CI 1.3-2.5), and emphysema (OR 1.8, 95% CI 1.1-3.1). The associations between occupational exposure to VGDF and chronic airflow limitation were weaker, and for the OR, the CIs included unity. The population-attributable fraction for occupational exposure to VGDF was 0.37 (95% CI 0.23-0.47) for COPD and 0.23 (95% CI 0.05-0.35) for emphysema.

Conclusion

The occupational burden of COPD and computed tomography-verified emphysema is substantial.

The Role of Computed Tomography for the Evaluation of Lung Disease in Alpha-1 Antitrypsin Deficiency

Alpha-1 antitrypsin deficiency (AATD) is characterized by low serum levels of or dysfunctional alpha-1 proteinase inhibitor. In the lung parenchyma, this results in a loss of protection against the activity of serine proteases, particularly neutrophil elastase. The resultant imbalance in protease and antiprotease activity leads to an increased risk for the development of early-onset emphysema and COPD. As in traditional smoke-related COPD, the assessment of the severity and disease progression of lung disease in AATD is conventionally based on lung function; however, pulmonary function tests are unable to discriminate between emphysema and airways disease, the two hallmark pathologic features of COPD. CT imaging has been used as a tool to further characterize lung structure and evaluate therapeutic interventions in AATD-related COPD. Moreover, recent advances in quantitative CT have significantly improved our assessment of the lung architecture, which has provided investigators and clinicians with a more detailed evaluation of the extent and severity of emphysema and airways disease in AATD. In addition, serial CT imaging measures are becoming increasingly important, as they provide a tool to monitor emphysema progression. This review describes the principles of CT technology and the role of CT imaging in assessing pulmonary disease progression in AATD, including the effect of therapeutic interventions.

Incidental perifissural nodules on routine chest computed tomography: lung cancer or not?

Objectives

Perifissural nodules (PFNs) are a common finding on chest CT, and are thought to represent non-malignant lesions. However, data outside a lung cancer-screening setting are currently lacking.

Methods

In a nested case-control design, out of a total cohort of 16,850 patients ≥ 40 years of age who underwent routine chest CT (2004-2012), 186 eligible subjects with incident lung cancer and 511 controls without were investigated. All non-calcified nodules ≥ 4 mm were semi-automatically annotated. Lung cancer location and subject characteristics were recorded.

Results

Cases (56 % male) had a median age of 64 years (IQR 59–70). Controls (60 % male) were slightly younger (p<0.01), median age of 61 years (IQR 51–70). A total of 262/1,278 (21 %) unique non-calcified nodules represented a PFN. None of these were traced to a lung malignancy over a median follow-up of around 4.5 years. PFNs were most often located in the lower lung zones (72 %, p<0.001). Median diameter was 4.6 mm (range: 4.0–8.1), volume 51 mm³ (range: 32–278). Some showed growth rates < 400 days.

Conclusions

Our data show that incidental PFNs do not represent lung cancer in a routine care, heterogeneous population. This confirms prior screening-based results.

Key Points

• One-fifth of non-calcified nodules represented a perifissural nodule in our non-screening population.

• PFNs fairly often show larger size, and can show interval growth.

• When morphologically resembling a PFN, nodules are nearly certainly not a malignancy.

• The assumed benign aetiology of PFNs seems valid outside the screening setting.

Cardiovascular risk in patients with alpha-1-antitrypsin deficiency

Background

Alpha-1-antitrypsin deficiency (AATD) is a rare inherited condition caused by mutations of the SERPINA1 gene that is associated with the development of a COPD like lung disease. The comorbidities in patients with AATD-related lung diseases are not well defined. The aim of this study was to analyze the clinical phenotype of AATD patients within the German COPD cohort study COSYCONET (“COPD and SYstemic consequences-COmorbidities NETwork”) cohort focusing on the distribution of comorbidities.

Method and results

The data from 2645 COSYCONET patients, including 139 AATD patients (110 with and 29 without augmentation therapy), were analyzed by descriptive statistics and regression analyses. We found significantly lower prevalence of cardiovascular comorbidities in AATD patients as compared to non-AATD COPD patients. After correction for age, pack years, body mass index, and sex, the differences were still significant for coronary artery disease (p = 0.002) and the prevalence of peripheral artery disease as determined by an ankle-brachial-index <= 0.9 (p = 0.035). Also the distribution of other comorbidities such as bronchiectasis differed between AATD and non-deficient COPD.

Conclusion

AATD is associated with a lower prevalence of cardiovascular disease, the underlying mechanisms need further investigation.

Electronic supplementary material

The online version of this article (10.1186/s12931-017-0655-1) contains supplementary material, which is available to authorized users.

Lung densitometry: why, how and when

Lung densitometry assesses with computed tomography (CT) the X-ray attenuation of the pulmonary tissue which reflects both the degree of inflation and the structural lung abnormalities implying decreased attenuation, as in emphysema and cystic diseases, or increased attenuation, as in fibrosis. Five reasons justify replacement with lung densitometry of semi-quantitative visual scales used to measure extent and severity of diffuse lung diseases: (I) improved reproducibility; (II) complete vs. discrete assessment of the lung tissue; (III) shorter computation times; (IV) better correlation with pathology quantification of pulmonary emphysema; (V) better or equal correlation with pulmonary function tests (PFT). Commercially and open platform software are available for lung densitometry. It requires attention to technical and methodological issues including CT scanner calibration, radiation dose, and selection of thickness and filter to be applied to sections reconstructed from whole-lung CT acquisition. Critical is also the lung volume reached by the subject at scanning that can be measured in post-processing and represent valuable information per se. The measurements of lung density include mean and standard deviation, relative area (RA) at -970, -960 or -950 Hounsfield units (HU) and 1st and 15th percentile for emphysema in inspiratory scans, and RA at -856 HU for air trapping in expiratory scans. Kurtosis and skewness are used for evaluating pulmonary fibrosis in inspiratory scans. The main indication for lung densitometry is assessment of emphysema component in the single patient with chronic obstructive pulmonary diseases (COPD). Additional emerging applications include the evaluation of air trapping in COPD patients and in subjects at risk of emphysema and the staging in patients with lymphangioleiomyomatosis (LAM) and with pulmonary fibrosis. It has also been applied to assess prevalence of smoking-related emphysema and to monitor progression of smoking-related emphysema, alpha1 antitrypsin deficiency emphysema, and pulmonary fibrosis. Finally, it is recommended as end-point in pharmacological trials of emphysema and lung fibrosis.

Chronic obstructive pulmonary disease with mild airflow limitation: current knowledge and proposal for future research - a consensus document from six scientific societies

Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality and morbidity worldwide, with high and growing prevalence. Its underdiagnosis and hence under-treatment is a general feature across all countries. This is particularly true for the mild or early stages of the disease, when symptoms do not yet interfere with daily living activities and both patients and doctors are likely to underestimate the presence of the disease. A diagnosis of COPD requires spirometry in subjects with a history of exposure to known risk factors and symptoms. Postbronchodilator forced expiratory volume in 1 second (FEV₁)/forced vital capacity <0.7 or less than the lower limit of normal confirms the presence of airflow limitation, the severity of which can be measured by FEV₁% predicted: stage 1 defines COPD with mild airflow limitation, which means postbronchodilator FEV₁ ≥80% predicted. In recent years, an elegant series of studies has shown that "exclusive reliance on spirometry, in patients with mild airflow limitation, may result in underestimation of clinically important physiologic impairment". In fact, exercise tolerance, diffusing capacity, and gas exchange can be impaired in subjects at a mild stage of airflow limitation. Furthermore, growing evidence indicates that smokers without overt abnormal spirometry have respiratory symptoms and undergo therapy. This is an essential issue in COPD. In fact, on one hand, airflow limitation, even mild, can unduly limit the patient's physical activity, with deleterious consequences on quality of life and even survival; on the other hand, particularly in younger subjects, mild airflow limitation might coincide with the early stage of the disease. Therefore, we thought that it was worthwhile to analyze further and discuss this stage of "mild COPD". To this end, representatives of scientific societies from five European countries have met and developed this document to stimulate the attention of the scientific community on COPD with "mild" airflow limitation. The aim of this document is to highlight some key features of this important concept and help the practicing physician to understand better what is behind "mild" COPD. Future research should address two major issues: first, whether mild airflow limitation represents an early stage of COPD and what the mechanisms underlying the evolution to more severe stages of the disease are; and second, not far removed from the first, whether regular treatment should be considered for COPD patients with mild airflow limitation, either to prevent progression of the disease or to encourage and improve physical activity or both.

Influence of fissure integrity on quantitative CT and emphysema distribution in emphysema-type COPD using a dedicated COPD software

OBJECTIVES

Fissure integrity (FI) plays a key role in selecting patients for interventional emphysema therapy. We investigated its interference with automated lobar segmentation in quantitative computed tomography (CT) and emphysema distribution.

METHODS

CT was available for 50 patients with chronic obstructive pulmonary disease (COPD). Lobe segmentation was performed fully automated by software and corrected manually. FI was evaluated visually using a %-scale. The influence of FI on emphysema ratio (ER=percentage of lung volume with density values<-950 HU), mean lung density (MLD), emphysema and total volume of adjacent lobes was analyzed. Lobe-based results were compared with respect to FI.

RESULTS

Differences in ER in adjacent lobes for complete vs. incomplete fissures were 12.4% for the right horizontal, 0.2% and 3% for the right oblique and 4.4% for the left oblique fissure (all p>0.05). Results for emphysema comparing automated vs. manually corrected segmentation exceeded clinically acceptable values, but were not significantly affected by FI (p>0.05). The widest limits of agreement for ER and MLD were noted in the right middle lobe ([-14, 17.4%], [-22.4, 32.4 Hounsfield Units]).

CONCLUSIONS

Automated lobe segmentation and emphysema distribution are not significantly affected by FI. Manual correction of automated lobar segmentation is still recommended in severe emphysema.

Influence of exposure parameters and iterative reconstruction on automatic airway segmentation and analysis on MDCT-An ex vivo phantom study

OBJECTIVES

To evaluate the influence of exposure parameters and raw-data-based iterative reconstruction (IR) on computer-aided segmentation and quantitative analysis of the tracheobronchial tree on multidetector computed tomography (MDCT).

MATERIAL AND METHODS

10 porcine heart-lung-explants were mounted inside a dedicated chest phantom. MDCT was performed at 120kV and 80kV with 120, 60, 30 and 12 mAs each. All scans were reconstructed with filtered back projection (FBP) or IR, resulting in a total of 160 datasets. The maximum number of detected airway segments, most peripheral airway generation detected, generation-specific airway wall thickness (WT), total diameter (TD) and normalized wall thickness (pi10) were compared.

RESULTS

The number of detected airway segments decreased slightly with dose (324.8±118 at 120kV/120mAs vs. 288.9±130 at 80kV/30mAs with FBP, p<0.05) and was not changed by IR. The 20th generation was constantly detected as most peripheral. WT did not change significantly with exposure parameters and reconstruction algorithm across all generations: range 1st generation 2.4-2.7mm, 5th 1.0-1.1mm, and 10th 0.7mm with FBP; 1st 2.3-2.4mm, 5th 1.0-1.1mm, and 10th 0.7-0.8mm with IR. pi10 was not affected as well (range 0.32-0.34mm).

CONCLUSIONS

Exposure parameters and IR had no relevant influence on measured airway parameters even for WT <1mm. Thus, no systematic errors would be expected using automatic airway analysis with low-dose MDCT and IR.

Cross-Sectional Study of Chronic Obstructive Pulmonary Disease Prevalence Among Smokers, Ex-Smokers, and Never-Smokers in Almaty, Kazakhstan: Study Protocol

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is significantly underdiagnosed in Kazakhstan, and there is no previously conducted study on COPD prevalence in the country.

OBJECTIVE

The purpose of this study is to assess the prevalence of COPD among individuals aged 40 to 59 years based on results of spirometry before and after bronchodilator, presence of structural changes in the lungs (emphysema, inflammatory changes, and thickening of the walls of the large and small airways) detected by computer tomography, and the symptoms of COPD. The study has 3 study groups: smokers of conventional cigarettes, those who had quit smoking 1 to 5 years ago, and those who haven't smoked cigarettes.

METHODS

This is an observational study with a cross-sectional design among individuals aged 40 to 59 years in Almaty, Kazakhstan. The sample of 900 individuals of both sexes contains 500 smokers, 200 ex-smokers, and 200 never-smokers. Study measures include spirometry, chest computed tomography, electrocardiography, physical exams, laboratory testing of serum, anthropometry, and 6-minute walk test. Data are collected by computer-assisted personal interviewing with tablets. The questionnaire was designed to explore possible COPD risk factors including history of smoking, current smoking, level of smoking exposure (in pack-years), passive smoking, occupational and environmental hazards, and covariates: age, gender, ethnicity, education, occupation, and self-reported morbidity. COPD Assessment Test (CAT) is used to collect information about COPD symptoms.

RESULTS

We have completed the participant recruitment and study procedures. Currently, we are working on data processing and data analysis. The authors anticipate the preliminary results should be available by September 2017. Study results will be published in peer-reviewed scientific journals.

CONCLUSIONS

This is the first study in Kazakhstan that assesses prevalence of COPD and its comorbidities in the adult population aged 40 to 59 years. The results of the study will be useful for improving COPD preventive measures, better COPD screening, identification, and registration. Findings of the study will also contribute to global knowledge on the epidemiology of COPD.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02926534; https://clinicaltrials.gov/ct2/show/NCT02926534 (Archived by WebCite at http://www.webcitation.org/6rjwGsPOZ).

Micro-Computed Tomography Comparison of Preterminal Bronchioles in Centrilobular and Panlobular Emphysema

RATIONALE

Very little is known about airways that are too small to be visible on thoracic multidetector computed tomography but larger than the terminal bronchioles.

OBJECTIVES

To examine the structure of preterminal bronchioles located one generation proximal to terminal bronchioles in centrilobular and panlobular emphysema.

METHODS

Preterminal bronchioles were identified by backtracking from the terminal bronchioles, and their centerlines were established along the entire length of their lumens. Multiple cross-sectional images perpendicular to the centerline were reconstructed to evaluate the bronchiolar wall and lumen, and the alveolar attachments to the outer airway walls in relation to emphysematous destruction in 28 lung samples from six patients with centrilobular emphysema, 20 lung samples from seven patients with panlobular emphysema associated with alpha-1 antitrypsin deficiency, and 47 samples from seven control (donor) lungs.

MEASUREMENTS AND MAIN RESULTS

The preterminal bronchiolar length, wall volume, total volume (wall + lumen), lumen circularity, and number of alveolar attachments were reduced in both centrilobular and panlobular emphysema compared with control lungs. In contrast, thickening of the wall and narrowing of the lumen were more severe and heterogeneous in centrilobular than in panlobular emphysema. The bronchiolar lumen was narrower in the middle than at both ends, and the decreased number of alveolar attachments was associated with increased wall thickness in centrilobular emphysema.

CONCLUSIONS

These results provide new information about small airways pathology in centrilobular and panlobular emphysema and show that these changes affect airways that are not visible with thoracic multidetector computed tomography scans but located proximal to the terminal bronchioles in chronic obstructive pulmonary disease.

Influence of lung CT changes in chronic obstructive pulmonary disease (COPD) on the human lung microbiome

BACKGROUND

Changes in microbial community composition in the lung of patients suffering from moderate to severe COPD have been well documented. However, knowledge about specific microbiome structures in the human lung associated with CT defined abnormalities is limited.

METHODS

Bacterial community composition derived from brush samples from lungs of 16 patients suffering from different CT defined subtypes of COPD and 9 healthy subjects was analyzed using a cultivation independent barcoding approach applying 454-pyrosequencing of 16S rRNA gene fragment amplicons.

RESULTS

We could show that bacterial community composition in patients with changes in CT (either airway or emphysema type changes, designated as severe subtypes) was different from community composition in lungs of patients without visible changes in CT as well as from healthy subjects (designated as mild COPD subtype and control group) (PC1, Padj = 0.002). Higher abundance of Prevotella in samples from patients with mild COPD subtype and from controls and of Streptococcus in the severe subtype cases mainly contributed to the separation of bacterial communities of subjects. No significant effects of treatment with inhaled glucocorticoids on bacterial community composition were detected within COPD cases with and without abnormalities in CT in PCoA. Co-occurrence analysis suggests the presence of networks of co-occurring bacteria. Four communities of positively correlated bacteria were revealed. The microbial communities can clearly be distinguished by their associations with the CT defined disease phenotype.

CONCLUSION

Our findings indicate that CT detectable structural changes in the lung of COPD patients, which we termed severe subtypes, are associated with alterations in bacterial communities, which may induce further changes in the interaction between microbes and host cells. This might result in a changed interplay with the host immune system.

Aging Airways: between Normal and Disease. A Multidimensional Diagnostic Approach by Combining Clinical, Functional, and Imaging Data

The lack of data on lung function decline in the aging process as well as the lack of gold standards to define obstructive and restrictive respiratory disease in older people point out the need for a multidimensional assessment and interpretation of the aging airways. By integrating clinical data together with morphologic and morphometric findings clinicians can assess the airways with a more comprehensive perspective, helpful in the interpretation of the "grey zone" between normal aging and disease. This review focuses on the value of a multidimensional approach in the study of the aging airways, including clinical findings, respiratory function tests, and imaging as parts of a whole. Nowadays this multidimensional diagnostic approach can be used in daily clinical practice. In next future, it can be implemented by the analysis of exhaled gases, post-processing imaging techniques, and genetic analysis, that will hopefully reduce the gaps in knowledge of normal aging and airway disease in older people.

CT-Based Local Distribution Metric Improves Characterization of COPD

Parametric response mapping (PRM) of paired CT lung images has been shown to improve the phenotyping of COPD by allowing for the visualization and quantification of non-emphysematous air trapping component, referred to as functional small airways disease (fSAD). Although promising, large variability in the standard method for analyzing PRMfSAD has been observed. We postulate that representing the 3D PRMfSAD data as a single scalar quantity (relative volume of PRMfSAD) oversimplifies the original 3D data, limiting its potential to detect the subtle progression of COPD as well as varying subtypes. In this study, we propose a new approach to analyze PRM. Based on topological techniques, we generate 3D maps of local topological features from 3D PRMfSAD classification maps. We found that the surface area of fSAD (SfSAD) was the most robust and significant independent indicator of clinically meaningful measures of COPD. We also confirmed by micro-CT of human lung specimens that structural differences are associated with unique SfSAD patterns, and demonstrated longitudinal feature alterations occurred with worsening pulmonary function independent of an increase in disease extent. These findings suggest that our technique captures additional COPD characteristics, which may provide important opportunities for improved diagnosis of COPD patients.

Chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) kills more than 3 million people worldwide every year. Despite progress in the treatment of symptoms and prevention of acute exacerbations, few advances have been made to ameliorate disease progression or affect mortality. A better understanding of the complex disease mechanisms resulting in COPD is needed. Smoking cessation programmes, increasing physical activity, and early detection and treatment of comorbidities are further key components to reduce the burden of the disease. However, without a global political and economic effort to reduce tobacco use, to regulate environmental exposure, and to find alternatives to the massive use of biomass fuel, COPD will remain a major health-care problem for decades to come.

Bronchiectasis in COPD patients: more than a comorbidity?

Computed tomography scan images have been used to identify different radiological COPD phenotypes based on the presence and severity of emphysema, bronchial wall thickening, and bronchiectasis. Bronchiectasis is defined as an abnormal dilation of the bronchi, usually as a result of chronic airway inflammation and/or infection. The prevalence of bronchiectasis in patients with COPD is high, especially in advanced stages. The identification of bronchiectasis in COPD has been defined as a different clinical COPD phenotype with greater symptomatic severity, more frequent chronic bronchial infection and exacerbations, and poor prognosis. A causal association has not yet been proven, but it is biologically plausible that COPD, and particularly the infective and exacerbator COPD phenotypes, could be the cause of bronchiectasis without any other known etiology, beyond any mere association or comorbidity. The study of the relationship between COPD and bronchiectasis could have important clinical implications, since both diseases have different and complementary therapeutic approaches. Longitudinal studies are needed to investigate the development of bronchiectasis in COPD, and clinical trials with treatments aimed at reducing bacterial loads should be conducted to investigate their impact on the reduction of exacerbations and improvements in the long-term evolution of the disease.

Computed tomographic findings in subjects who died from respiratory disease in the National Lung Screening Trial

We evaluated the prevalence of significant lung abnormalities on computed tomography (CT) in patients who died from a respiratory illness other than lung cancer in the National Lung Screening Trial (NLST).

In this retrospective case–control study, NLST participants in the CT arm who died of respiratory illness other than lung cancer were matched for age, sex, pack-years and smoking status to a surviving control. A chest radiologist and a radiology resident blinded to the outcome independently scored baseline CT scans visually and qualitatively for the presence of emphysema, airway wall thickening and fibrotic lung disease. The prevalence of CT abnormalities was compared between cases and controls by using chi-squared tests.

In total, 167 participants died from a respiratory cause other than lung cancer. The prevalence of severe emphysema, airway wall thickening and fibrotic lung disease were 28.7% versus 4.8%, 26.9% versus 13.2% and 18.6% versus 0.5% in cases and controls, respectively. Radiological findings were significantly more prevalent in deaths compared with controls (all p<0.001).

CT-diagnosed severe emphysema, airway wall thickening and fibrosis were much more common in NLST participants who died from respiratory disease, and CT may provide an additional means of identifying these diseases.

CT Findings, Radiologic-Pathologic Correlation, and Imaging Predictors of Survival for Patients With Interstitial Pneumonia With Autoimmune Features

OBJECTIVE

The objective of this study is to determine the CT findings and patterns of interstitial pneumonia with autoimmune features (IPAF) and to assess whether imaging can predict survival for patients with IPAF.

MATERIALS AND METHODS

The study included 136 subjects who met the criteria for IPAF and had diagnostic-quality chest CT scans obtained from 2006 to 2015; a total of 74 of these subjects had pathologic samples available for review within 1 year of chest CT examination. CT findings and the presence of an usual interstitial pneumonitis (UIP) pattern of disease were assessed, as was the UIP pattern noted on pathologic analysis. Analysis of chest CT findings associated with survival was performed using standard univariate and multivariate Cox proportional hazards methods as well as the unadjusted log-rank test. Survival data were visually presented using the Kaplan-Meier survival curve estimator.

RESULTS

Most subjects with IPAF (57.4%; 78/136) had a high-confidence diagnosis of a UIP pattern on CT. Substantially fewer subjects (28.7%; 39/136) had a pattern that was inconsistent with UIP noted on CT. The presence of a UIP pattern on CT was associated with smoking (p < 0.01), male sex (p < 0.01), and older age (p < 0.001). Approximately one-fourth of the subjects had a nonspecific interstitial pneumonitis pattern on CT. Of interest, nearly one-tenth of the subjects had a CT pattern that was most consistent with hypersensitivity pneumonitis rather than the customary CT patterns ascribed to lung disease resulting from connective tissue disease. Most subjects with a possible UIP pattern on CT (83.3%) had UIP diagnosed on the basis of pathologic findings. Focused multivariate analysis showed that honeycombing on CT (hazard ratio, 2.17; 95% CI, 1.05-4.47) and pulmonary artery enlargement on CT (hazard ratio, 2.08; 95% CI, 1.02-4.20) were independent predictors of survival.

CONCLUSION

IPAF most often presents with a UIP pattern on CT and is associated with worse survival when concomitant honeycombing or pulmonary artery enlargement is present.

Emphysema quantification and lung volumetry in chest X-ray equivalent ultralow dose CT - Intra-individual comparison with standard dose CT

OBJECTIVES

To determine whether ultralow dose chest CT with tin filtration can be used for emphysema quantification and lung volumetry and to assess differences in emphysema measurements and lung volume between standard dose and ultralow dose CT scans using advanced modeled iterative reconstruction (ADMIRE).

METHODS

84 consecutive patients from a prospective, IRB-approved single-center study were included and underwent clinically indicated standard dose chest CT (1.7±0.6mSv) and additional single-energy ultralow dose CT (0.14±0.01mSv) at 100kV and fixed tube current at 70mAs with tin filtration in the same session. Forty of the 84 patients (48%) had no emphysema, 44 (52%) had emphysema. One radiologist performed fully automated software-based pulmonary emphysema quantification and lung volumetry of standard and ultralow dose CT with different levels of ADMIRE. Friedman test and Wilcoxon rank sum test were used for multiple comparison of emphysema and lung volume. Lung volumes were compared using the concordance correlation coefficient.

RESULTS

The median low-attenuation areas (LAA) using filtered back projection (FBP) in standard dose was 4.4% and decreased to 2.6%, 2.1% and 1.8% using ADMIRE 3, 4, and 5, respectively. The median values of LAA in ultralow dose CT were 5.7%, 4.1% and 2.4% for ADMIRE 3, 4, and 5, respectively. There was no statistically significant difference between LAA in standard dose CT using FBP and ultralow dose using ADMIRE 4 (p=0.358) as well as in standard dose CT using ADMIRE 3 and ultralow dose using ADMIRE 5 (p=0.966). In comparison with standard dose FBP the concordance correlation coefficients of lung volumetry were 1.000, 0.999, and 0.999 for ADMIRE 3, 4, and 5 in standard dose, and 0.972 for ADMIRE 3, 4 and 5 in ultralow dose CT.

CONCLUSIONS

Ultralow dose CT at chest X-ray equivalent dose levels allows for lung volumetry as well as detection and quantification of emphysema. However, longitudinal emphysema analyses should be performed with the same scan protocol and reconstruction algorithms for reproducibility.

Standardizing CT lung density measure across scanner manufacturers

PURPOSE

Computed Tomography (CT) imaging of the lung, reported in Hounsfield Units (HU), can be parameterized as a quantitative image biomarker for the diagnosis and monitoring of lung density changes due to emphysema, a type of chronic obstructive pulmonary disease (COPD). CT lung density metrics are global measurements based on lung CT number histograms, and are typically a quantity specifying either the percentage of voxels with CT numbers below a threshold, or a single CT number below which a fixed relative lung volume, nth percentile, falls. To reduce variability in the density metrics specified by CT attenuation, the Quantitative Imaging Biomarkers Alliance (QIBA) Lung Density Committee has organized efforts to conduct phantom studies in a variety of scanner models to establish a baseline for assessing the variations in patient studies that can be attributed to scanner calibration and measurement uncertainty.

METHODS

Data were obtained from a phantom study on CT scanners from four manufacturers with several protocols at various tube potential voltage (kVp) and exposure settings. Free from biological variation, these phantom studies provide an assessment of the accuracy and precision of the density metrics across platforms solely due to machine calibration and uncertainty of the reference materials. The phantom used in this study has three foam density references in the lung density region, which, after calibration against a suite of Standard Reference Materials (SRM) foams with certified physical density, establishes a HU-electron density relationship for each machine-protocol. We devised a 5-step calibration procedure combined with a simplified physical model that enabled the standardization of the CT numbers reported across a total of 22 scanner-protocol settings to a single energy (chosen at 80 keV). A standard deviation was calculated for overall CT numbers for each density, as well as by scanner and other variables, as a measure of the variability, before and after the standardization. In addition, a linear mixed-effects model was used to assess the heterogeneity across scanners, and the 95% confidence interval of the mean CT number was evaluated before and after the standardization.

RESULTS

We show that after applying the standardization procedures to the phantom data, the instrumental reproducibility of the CT density measurement of the reference foams improved by more than 65%, as measured by the standard deviation of the overall mean CT number. Using the lung foam that did not participate in the calibration as a test case, a mixed effects model analysis shows that the 95% confidence intervals are [-862.0 HU, -851.3 HU] before standardization, and [-859.0 HU, -853.7 HU] after standardization to 80 keV. This is in general agreement with the expected CT number value at 80 keV of -855.9 HU with 95% CI of [-857.4 HU, -854.5 HU] based on the calibration and the uncertainty in the SRM certified density.

CONCLUSIONS

This study provides a quantitative assessment of the variations expected in CT lung density measures attributed to non-biological sources such as scanner calibration and scanner x-ray spectrum and filtration. By removing scanner-protocol dependence from the measured CT numbers, higher accuracy and reproducibility of quantitative CT measures were attainable. The standardization procedures developed in study may be explored for possible application in CT lung density clinical data.

The Pathology of Chronic Obstructive Pulmonary Disease: Progress in the 20th and 21st Centuries

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and is the fourth leading cause of death worldwide. There has been significant progress in the pathologic description and pathophysiologic analysis of COPD in the 20th and 21st centuries. We review the history, progression, and significance of pathologic alterations in COPD, including emphysematous changes, airway alterations, and vascular alterations. We also indicate what pathologic features of COPD the practicing pathologist should be describing in standard surgical and autopsy specimens.

Antibody deficiency in patients with frequent exacerbations of Chronic Obstructive Pulmonary Disease (COPD)

Chronic Obstructive Pulmonary Disease is the third leading cause of death in the US, and is associated with periodic exacerbations, which account for the largest proportion of health care utilization, and lead to significant morbidity, mortality, and worsening lung function. A subset of patients with COPD have frequent exacerbations, occurring 2 or more times per year. Despite many interventions to reduce COPD exacerbations, there is a significant lack of knowledge in regards to their mechanisms and predisposing factors. We describe here an important observation that defines antibody deficiency as a potential risk factor for frequent COPD exacerbations. We report a case series of patients who have frequent COPD exacerbations, and who were found to have an underlying primary antibody deficiency syndrome. We also report on the outcome of COPD exacerbations following treatment in a subset with of these patients with antibody deficiency. We identified patients with COPD who had 2 or more moderate to severe exacerbations per year; immune evaluation including serum immunoglobulin levels and pneumococcal IgG titers was performed. Patients diagnosed with an antibody deficiency syndrome were treated with either immunoglobulin replacement therapy or prophylactic antibiotics, and their COPD exacerbations were monitored over time. A total of 42 patients were identified who had 2 or more moderate to severe COPD exacerbations per year. Twenty-nine patients had an underlying antibody deficiency syndrome: common variable immunodeficiency (8), specific antibody deficiency (20), and selective IgA deficiency (1). Twenty-two patients had a follow-up for at least 1 year after treatment of their antibody deficiency, which resulted in a significant reduction of COPD exacerbations, courses of oral corticosteroid use and cumulative annual dose of oral corticosteroid use, rescue antibiotic use, and hospitalizations for COPD exacerbations. This case series identifies antibody deficiency as a potentially treatable risk factor for frequent COPD exacerbations; testing for antibody deficiency should be considered in difficult to manage frequently exacerbating COPD patients. Further prospective studies are warranted to further test this hypothesis.

A Bayesian Nonparametric Model for Disease Subtyping: Application to Emphysema Phenotypes

We introduce a novel Bayesian nonparametric model that uses the concept of disease trajectories for disease subtype identification. Although our model is general, we demonstrate that by treating fractions of tissue patterns derived from medical images as compositional data, our model can be applied to study distinct progression trends between population subgroups. Specifically, we apply our algorithm to quantitative emphysema measurements obtained from chest CT scans in the COPDGene Study and show several distinct progression patterns. As emphysema is one of the major components of chronic obstructive pulmonary disease (COPD), the third leading cause of death in the United States [1], an improved definition of emphysema and COPD subtypes is of great interest. We investigate several models with our algorithm, and show that one with age , pack years (a measure of cigarette exposure), and smoking status as predictors gives the best compromise between estimated predictive performance and model complexity. This model identified nine subtypes which showed significant associations to seven single nucleotide polymorphisms (SNPs) known to associate with COPD. Additionally, this model gives better predictive accuracy than multiple, multivariate ordinary least squares regression as demonstrated in a five-fold cross validation analysis. We view our subtyping algorithm as a contribution that can be applied to bridge the gap between CT-level assessment of tissue composition to population-level analysis of compositional trends that vary between disease subtypes.

Evaluation of pulmonary function using single-breath-hold dual-energy computed tomography with xenon: Results of a preliminary study

Xenon-enhanced dual-energy computed tomography (xenon-enhanced CT) can provide lung ventilation maps that may be useful for assessing structural and functional abnormalities of the lung. Xenon-enhanced CT has been performed using a multiple-breath-hold technique during xenon washout. We recently developed xenon-enhanced CT using a single-breath-hold technique to assess ventilation. We sought to evaluate whether xenon-enhanced CT using a single-breath-hold technique correlates with pulmonary function testing (PFT) results.Twenty-six patients, including 11 chronic obstructive pulmonary disease (COPD) patients, underwent xenon-enhanced CT and PFT. Three of the COPD patients underwent xenon-enhanced CT before and after bronchodilator treatment. Images from xenon-CT were obtained by dual-source CT during a breath-hold after a single vital-capacity inspiration of a xenon-oxygen gas mixture. Image postprocessing by 3-material decomposition generated conventional CT and xenon-enhanced images.Low-attenuation areas on xenon images matched low-attenuation areas on conventional CT in 21 cases but matched normal-attenuation areas in 5 cases. Volumes of Hounsfield unit (HU) histograms of xenon images correlated moderately and highly with vital capacity (VC) and total lung capacity (TLC), respectively (r = 0.68 and 0.85). Means and modes of histograms weakly correlated with VC (r = 0.39 and 0.38), moderately with forced expiratory volume in 1 second (FEV1) (r = 0.59 and 0.56), weakly with the ratio of FEV1 to FVC (r = 0.46 and 0.42), and moderately with the ratio of FEV1 to its predicted value (r = 0.64 and 0.60). Mode and volume of histograms increased in 2 COPD patients after the improvement of FEV1 with bronchodilators. Inhalation of xenon gas caused no adverse effects.Xenon-enhanced CT using a single-breath-hold technique depicted functional abnormalities not detectable on thin-slice CT. Mode, mean, and volume of HU histograms of xenon images reflected pulmonary function. Xenon images obtained with xenon-enhanced CT using a single-breath-hold technique can qualitatively depict pulmonary ventilation. A larger study comprising only COPD patients should be conducted, as xenon-enhanced CT is expected to be a promising technique for the management of COPD.

Lung disease recalling paraseptal emphysema in a patient with Goltz syndrome

Background

Goltz syndrome is a rare, genetic disorder mainly occurring in female patients.

Case presentation

The case presented here is, to the best of our knowledge, the first description of the occurrence of lung parenchymal alterations in a young female patient affected by Goltz syndrome. Although pulmonary involvement is not known in patients affected by X-linked Goltz syndrome, the case here described is related to the even rarer autosomal form of the disease, as in this case. It is thus conceivable that in such different genetic setting the involvement of lung parenchyma may be unveiled through atypical emphysematous lesions.

Conclusion

This report suggested - for the first time time - a rationale for a lung function and imaging screening in patients affected by Goltz syndrome at least in its autosomal form.

Parametric response mapping on chest computed tomography associates with clinical and functional parameters in chronic obstructive pulmonary disease

BACKGROUND

In the search for specific phenotypes of chronic obstructive pulmonary disease (COPD) computed tomography (CT) derived Parametric Response Mapping (PRM) has been introduced. This study evaluates the association between PRM and currently available biomarkers of disease severity in COPD.

METHODS

Smokers with and without COPD were characterized based on questionnaires, pulmonary function tests, body plethysmography, and low-dose chest CT scanning. PRM was used to calculate the amount of emphysema (PRM^Emph) and non-emphysematous air trapping (i.e. functional small airway disease, PRM^fSAD). PRM was first compared with other biomarkers for emphysema (Perc15) and air trapping (E/I-ratio_MLD). Consequently, linear regression models were utilized to study associations of PRM measurements with clinical parameters.

RESULTS

166 participants were included with a mean ± SD age of 50.5 ± 17.7 years. Both PRM^Emph and PRM^fSAD were more strongly correlated with lung function parameters as compared to Perc15 and E/I-ratio_MLD. PRM^Emph and PRM^fSAD were higher in COPD participants than non-COPD participants (14.0% vs. 1.1%, and 31.6% vs. 8.2%, respectively, both p < 0.001) and increased with increasing GOLD stage (all p < 0.001). Multivariate analysis showed that PRM^fSAD was mainly associated with total lung capacity (TLC) (β = -7.90, p < 0.001), alveolar volume (VA) (β = 7.79, p < 0.001), and residual volume (β = 6.78, p < 0.001), whilst PRM^Emph was primarily associated with Kco (β = 8.95, p < 0.001), VA (β = -6.21, p < 0.001), and TLC (β = 6.20, p < 0.001).

CONCLUSIONS

PRM strongly associates with the presence and severity of COPD. PRM therefore appears to be a valuable tool in differentiating COPD phenotypes.

Findings on Thoracic Computed Tomography Scans and Respiratory Outcomes in Persons with and without Chronic Obstructive Pulmonary Disease: A Population-Based Cohort Study

BACKGROUND

Thoracic computed tomography (CT) scans are widely performed in clinical practice, often leading to detection of airway or parenchymal abnormalities in asymptomatic or minimally symptomatic individuals. However, clinical relevance of CT abnormalities is uncertain in the general population.

METHODS

We evaluated data from 1361 participants aged ≥40 years from a Canadian prospective cohort comprising 408 healthy never-smokers, 502 healthy ever-smokers, and 451 individuals with spirometric evidence of chronic obstructive pulmonary disease (COPD) who had thoracic CT scans. CT images of subjects were visually scored for respiratory bronchiolitis(RB), emphysema(E), bronchial-wall thickening(BWT), expiratory air-trapping(AT), and bronchiectasis(B). Multivariable logistic regression models were used to assess associations of CT features with respiratory symptoms, dyspnea, health status as determined by COPD assessment test, and risk of clinically significant exacerbations during 12 months follow-up.

RESULTS

About 11% of life-time never-smokers demonstrated emphysema on CT scans. Prevalence increased to 30% among smokers with normal lung function and 36%, 50%, and 57% among individuals with mild, moderate or severe/very severe COPD, respectively. Presence of emphysema on CT was associated with chronic cough (OR,2.11; 95%CI,1.4-3.18); chronic phlegm production (OR,1.87; 95% CI,1.27-2.76); wheeze (OR,1.61; 95% CI,1.05-2.48); dyspnoea (OR,2.90; 95% CI,1.41-5.98); CAT score≥10(OR,2.17; 95%CI,1.42-3.30) and risk of ≥2 exacerbations over 12 months (OR,2.17; 95% CI, 1.42-3.0).

CONCLUSIONS

Burden of thoracic CT abnormalities is high among Canadians ≥40 years of age, including never-smokers and smokers with normal lung function. Detection of emphysema on CT scans is associated with pulmonary symptoms and increased risk of exacerbations, independent of smoking or lung function.

Clinical-Radiologic-Pathologic Correlation of Smoking-Related Diffuse Parenchymal Lung Disease

The direct toxicity of cigarette smoke and the body's subsequent response to this lung injury leads to a wide array of pathologic manifestations and disease states that lead to both reversible and irreversible injury to the large airways, small airways, alveolar walls, and alveolar spaces. These include emphysema, bronchitis, bronchiolitis, acute eosinophilic pneumonia, pulmonary Langerhans cell histiocytosis, respiratory bronchiolitis, desquamative interstitial pneumonia, and pulmonary fibrosis. Although these various forms of injury have different pathologic and imaging manifestations, they are all part of the spectrum of smoking-related diffuse parenchymal lung disease.

Risk of Lung Disease in PI MZ Heterozygotes. Current Status and Future Research Directions

The potential for increased chronic obstructive pulmonary disease (COPD) risk among PI MZ subjects was initially recognized decades ago. However, despite many studies of this topic, it has remained controversial whether such increased risk exists. Several recent studies in large populations strongly support increased risk for COPD among PI MZ subjects. This increased PI MZ risk will need to be understood in the context of other identified COPD genetic determinants and investigations of COPD phenotypic heterogeneity.