Pattern Of Emphysema Research Articles

Advanced interstitial lung fibrosis with emphysema and pulmonary hypertension with no evidence for interstitial lung disease on high resolution CT.

The diagnosis of idiopathic pulmonary arterial hypertension (iPAH) is complex and, besides invasive hemodynamic evaluation, includes several diagnostic steps to exclude any underlying diseases. The role of a decreased diffusion capacity of the lung for carbon monoxide (DLCO) is a matter of discussion. Here, we present a 76-year-old man with a smoking history of 30 pack-years who was diagnosed with iPAH after chronic thromboembolic pulmonary hypertension was excluded based on a negative perfusion scan, an underlying heart disease was excluded based on echocardiography and right heart catheterization, and a significant lung disease was excluded based on lung function test (FVC = 101% predicted, FEV1 = 104% predicted, FEV1/FVC = 77, TLC = 97% predicted) and thin-slice computed tomography (CT) scan. Just DLCO was reduced to 40% predicted, suggesting a possible structural lung disease. Postmortem examination demonstrated severe interstitial lung fibrosis combined with microscopic emphysema. This indicates that both CT imaging and pulmonary function test may be insensitive to a diffuse peripheral combined pattern of fibrosis and emphysema and that DLCO may be the only sensitive marker of this significant lung pathology.

Applicability of color-coded computed tomography images in lung volume reduction surgery planning.

Adequate patient selection is the key to successful lung volume reduction in patients with pulmonary emphysema. Computed tomography (CT) enables a reliable detection of pulmonary emphysema and allows an accurate quantification of the severity. Our goal was to investigate the usefulness and reliability of color-coded (CC) CT images in classification of emphysema and preoperative lung volume reduction planning. Fifty patients undergoing lung volume reduction surgery at our institution between September 2015 and February 2016 were retrospectively investigated. Three readers visually assessed the amount and distribution patterns of pulmonary emphysema on axial, multi-planar and CC CT images using the Goddard scoring system and a surgically oriented grading system (bilateral markedly heterogenous, bilateral intermediately heterogenous, bilateral homogenous and unilateral heterogenous emphysema). Observer dependency was investigated by using Fleiss' kappa (κ) and the intraclass correlation coefficient (ICC). Results were compared to quantitative results from densitometry measurements and lung perfusion scintigraphy by using Spearman correlation. Recommendations for lung volume reduction sites based on emphysema amount and distribution of all readers were compared to removal sites from the surgical reports. Inter-rater agreement for emphysema distribution rating was substantial for CC images (κ=0.70; 95% CI, 0.64-0.80) and significantly better compared to axial and multiplanar images (P≤0.001). The inter-rater agreement for recommended segment removal was moderate for CC images (κ=0.56; 95% CI, 0.49-0.63) and significantly better compared to axial and multiplanar images (P<0.001). Visual emphysema rating correlated significantly with measurements from densitometry and perfusion scintigraphy in the upper and lower lung zones in all image types. CC CT images allow a precise, less observer-dependent evaluation of distribution of pulmonary emphysema and resection recommendation compared to axial and multiplanar CT images and might therefore be useful in lung volume resection surgery planning.

Imaging Advances in Chronic Obstructive Pulmonary Disease. Insights from the Genetic Epidemiology of Chronic Obstructive Pulmonary Disease (COPDGene) Study.

The Genetic Epidemiology of Chronic Obstructive Pulmonary Disease (COPDGene) study, which began in 2007, is an ongoing multicenter observational cohort study of more than 10,000 current and former smokers. The study is aimed at understanding the etiology, progression, and heterogeneity of chronic obstructive pulmonary disease (COPD). In addition to genetic analysis, the participants have been extensively characterized by clinical questionnaires, spirometry, volumetric inspiratory and expiratory computed tomography, and longitudinal follow-up, including follow-up computed tomography at 5 years after enrollment. The purpose of this state-of-the-art review is to summarize the major advances in our understanding of COPD resulting from the imaging findings in the COPDGene study. Imaging features that are associated with adverse clinical outcomes include early interstitial lung abnormalities, visual presence and pattern of emphysema, the ratio of pulmonary artery to ascending aortic diameter, quantitative evaluation of emphysema, airway wall thickness, and expiratory gas trapping. COPD is characterized by the early involvement of the small conducting airways, and the addition of expiratory scans has enabled measurement of small airway disease. Computational advances have enabled indirect measurement of nonemphysematous gas trapping. These metrics have provided insights into the pathogenesis and prognosis of COPD and have aided early identification of disease. Important quantifiable extrapulmonary findings include coronary artery calcification, cardiac morphology, intrathoracic and extrathoracic fat, and osteoporosis. Current active research includes identification of novel quantitative measures for emphysema and airway disease, evaluation of dose reduction techniques, and use of deep learning for phenotyping COPD.

Effect of Lung Volume Reduction Surgery on Respiratory Muscle Strength in Advanced Emphysema.

Background: Long-term effects of lung volume reduction surgery (LVRS) on respiratory muscle strength and effects of age, sex, and emphysema pattern on these changes are unknown. Therefore, we aimed to determine the long-term effect of LVRS on respiratory muscle strength changes in severe emphysema. Methods: The National Emphysema Treatment Trial was a prospective controlled multicentered trial, comparing LVRS to optimal medical treatment on survival and maximal exercise capacity. We examined percentage change in maximum inspiratory pressure (MIP) from baseline to 36 months follow-up to determine impact of LVRS as well as age, sex, emphysema pattern and exercise capacity on changes in MIP compared to medical treatment. Results: LVRS individuals had significantly greater increases in MIP from baseline compared to medical individuals at all follow-ups (LVRS 19.8 ± 42.3%, medical 3.2 ± 29.3%, p<0.0001, 12 months). The LVRS group had significant decreases in total lung capacity (TLC), residual volume (RV), functional residual capacity (FRC) and RV/TLC compared to the medical arm at all follow-up periods. Males and individuals 65-70 years of age had significantly greater increases in MIP following LVRS compared to the medical arm at all follow-ups; this same relationship was seen at up to 24 months for low exercise capacity, upper lobe predominant emphysema. Conclusions: LVRS significantly increases inspiratory muscle strength up to 3 years post-operatively, with male sex, age 65-70 years and low exercise capacity, upper lobe predominant emphysema especially associated with increased MIP. Inspiratory muscle strength increases were associated with decreases in non-invasive markers of dynamic hyperinflation, suggesting that LVRS allows inspiratory muscles to return to their optimal length-tension relationship.

Quantitative assessment of airway and parenchymal components of chronic obstructive pulmonary disease using thin-section helical computed tomography.

PurposeThe purpose of this study was to diagnose and characterise chronic obstructive pulmonary disease (COPD) into its forms, patterns, and severity using MDCT.Material and methodsIn this prospective study, spirometric and MDCT evaluation was done in 52 consecutive patients diagnosed with COPD. In each patient six segmental bronchi were evaluated for CT morphometric indices of bronchial wall thickness (BWT) and wall area percentage (WAP). Quantitative evaluation of emphysema was done using inbuilt software, and volume of emphysematous lung was determined using percentage low attenuation area (LAA). COPD was categorised into the following: emphysema predominant; airway predominant; or mixed phenotypes, and severity grading was assigned as mild, moderate, or severe.ResultsCentrilobular was the predominant emphysema pattern occurring alone (36.5%) or in combination with paraseptal changes (34.6%). Among COPD phenotypes, emphysema predominant was the commonest (44.3%), followed by mixed (30.8%), and bronchitis predominant (25.0%). The mean BWT in the airway-predominant group was significantly higher (1.94 ± 0.28 mm) than in the emphysema-predominant subgroup (1.79 ± 0.23 mm) with a p value of 0.005.ConclusionMDCT is an indispensable tool in quantitative and qualitative evaluation of COPD patients. Measurement of CT indices like BWT, WAP, and %LAA can reliably categorise COPD into phenotypes like emphysema predominant, airway predominant, or mixed, which serve as a guide for patient management.

Similarities in the Computed Tomography Appearance in α1-Antitrypsin Deficiency and Smoking-Related Chronic Obstructive Pulmonary Disease in a Smoking Collective

Background: Emphysematous destruction of lung parenchyma visible in computed tomography (CT) can be attributed to chronic obstructive pulmonary disease (COPD) or to α1-antitrypsin deficiency (AATD). Objectives: We evaluated if visual semiquantitative phenotyping of CT data helps identifying individuals with AATD in a group of smokers with severe emphysema and airflow limitation. Method: n = 14 patients with AATD and n = 15 with COPD and a minimum of 10 pack years underwent CT, clinical assessment, and full-body plethysmography. The extent and type of emphysema as well as large and small airway changes were rated semiquantitatively for each lobe using a standardized previously published scoring system. Lastly, a final diagnosis for each patient was proposed. Results: AATD had a significantly lower mean emphysema score than COPD, with 8.9 ± 3.4 versus 11.9 ± 3.2 (p < 0.001), respectively. Within both groups, there was significantly more emphysema in the lower lobes (p < 0.05–0.001). The COPD group showed an upper- and middle-lobe predominance of emphysema distribution when compared to the AATD group (p < 0.001). Centrilobular (CLE) and panlobular (PLE) emphysema patterns showed a uniform distribution within both groups, with a CLE predominance in the upper lung and a PLE predominance in the lower lung regions. AATD and COPD both showed significantly more airway changes in lower lobes compared to upper lobes (p = 0.05–0.001), without significant differences between both groups. Conclusion: The typical emphysema distribution patterns seen on CT traditionally assigned to AATD and COPD were of little use in discriminating both entities. Also, airway changes could not contribute to a more precise differentiation. We conclude that a concise standardized phenotyping-driven approach to chest CT in emphysema is not sufficient to identify patients with AATD in a cohort of smokers with advanced emphysema.

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

PurposeTo determine whether visually assessed patterns of emphysema at CT might provide a simple assessment of mortality risk among cigarette smokers.Materials and MethodsOf 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).ResultsObserver 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.ConclusionThe 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.

Identification of emphysema patterns in high resolution computed tomography images

Fractal dimension (FD) is a very useful metric for the analysis of image structures with statistically self-similar properties. It has applications in areas such as texture segmentation, shape classification and analysis of medical images. Several approaches can be used for calculating the fractal dimension of digital images; the most popular method is the box-counting method. It is also very challenging and difficult to classify patterns in high resolution computed tomography images (HRCT) using this important descriptor. This paper applied the Holder exponent computation of the local intensity values for detecting the emphysema patterns in HRCT images. The absolute differences between the normal and the abnormal regions in the images are the key for a successful classification of emphysema patterns using the statistical analysis. The results obtained in this paper demonstrated the effectiveness of the predictive power of the features extracted from the Holder exponent in the analysis and classification of HRCT images. The overall classification accuracy achieved in lung tissue layers is greater than 90%, which is an evidence to prove the effectiveness of the methods investigated in this paper.

Imaging aspects of interstitial lung disease in patients with rheumatoid arthritis: Literature review.

Interstitial lung disease (ILD) is a frequent and severe complication of rheumatoid arthritis (RA), resulting in pulmonary fibrosis (PF) and respiratory failure. Chest computed tomography (CT-c) or high resolution CT (HRCT) is the main modality for assessment of ILD. We performed a systematic literature review on CT-c/HRCT findings in patients with ILD-RA, using the MEDLINE database for the period from 1991 to 2015. Findings on CT-c/HRCT attributed to ILD-RA are variable (ground glass opacities, reticular and nodular pattern, as well as a combined pattern of emphysema and PF). Correlation of CT-c/HRCT findings with clinical data is inconsistent. ILD-RA is part of a general autoimmune inflammation and should be integrated into the decision-making process for the treatment of RA. There is an unmet need to design an algorithm which will allow prediction of CT-c changes compatible with ILD-RA with a high probability. Hopefully, this will enable treating patients with ILD-RA early, with possible halting of the progression of ILD-RA toward PF.

Quantitative Computed Tomography (CT) Assessment of Emphysema in Patients with Severe Chronic Obstructive Pulmonary Disease (COPD) and its Correlation with Age, Sex, Pulmonary Function Tests, BMI, Smoking, and Biomass Exposure

SummaryBackgroundTo evaluate the role of HRCT in quantifying emphysema in severe COPD patients and to study the variations in the pattern of emphysema in relation to age, sex, FEV1, smoking index, biomass exposure, and BMI.Material/MethodsAutomatic lung segmentation of HRCT scans in 41 severe COPD patients (GOLD stage III or more) was done using an emphysema protocol. The extent of emphysema was assessed using the density mask method with a threshold of –950 HU (%LAA-950). The percentage of emphysema in each lung lobe and both lungs was correlated with 6 parameters – age, sex, BMI, smoking index, biomass exposure, and FEV1.ResultsSmoking resulted in homogenously distributed emphysema regardless of the severity of smoking. BMI was inversely correlated with the extent of emphysema. A significant association was found between the percentage of emphysema in the right lower lobe and BMI (P=0.015), between biomass exposure and the percentage of emphysema in RUL, RLL, and both lungs (P values of 0.024, 0.016, and 0.036, respectively). The extent of emphysema was disproportionately low compared to the amount of obstruction on PFTs, indicating an airway predominant variety of COPD with significant biomass exposure.ConclusionsSmoking is associated with a relatively homogenous distribution of emphysema with no regional predilection. Biomass exposure produces predominantly right-sided emphysema. BMI decreases with increasing levels of emphysema in the right lower lobe. These risk factors of emphysema patterns are helpful in deciding on the management, including surgical options.

Computed Tomography-based Subclassification of Chronic Obstructive Pulmonary Disease.

Computed tomography (CT) is an obvious modality for subclassification of COPD. Traditionally, the pulmonary involvement of chronic obstructive pulmonary disease (COPD) in smokers is understood as a combination of deleterious effects of smoking on small airways (chronic bronchitis and small airways disease) and distal to the airways with destruction and loss of lung parenchyma (emphysema). However, segmentation of airways is still experimental; with contemporary high-resolution CT (HRCT) we can just see the "entrance" of small airways, and until now changes in airway morphology that have been observed in COPD are subtle. Furthermore, recent results indicate that emphysema may also be the essential pathophysiologic mechanism behind the airflow limitation of COPD. The definition of COPD excludes bronchiectasis as a symptomatic subtype of COPD, and CT findings in chronic bronchitis and exacerbations of COPD are rather unspecific. This leaves emphysema as the most obvious candidate for subclassification of COPD. Both chest radiologists and pulmonary physicians are quite familiar with the appearance of various patterns of emphysema on HRCT, such as centrilobular, panlobular, and paraseptal emphysema. However, it has not yet been possible to develop operational definitions of these patterns that can be used by computer software to automatically classify CT scans into distinct patterns. In conclusion, even though various emphysema patterns can be recognized visually, CT has not yet demonstrated a great potential for automated subclassification of COPD, and it is an open question whether it will ever be possible to achieve success equivalent to that obtained by HRCT in the area of interstitial lung diseases.

PiSZ alpha-1 antitrypsin deficiency (AATD): pulmonary phenotype and prognosis relative to PiZZ AATD and PiMM COPD

IntroductionThe PiSZ genotype results in less severe deficiency of alpha-1 antitrypsin (AAT) than PiZZ. Less is known about phenotypic and prognostic features.MethodsWe studied 699 PiZZ, 126 PiSZ and 316 PiMM...

P58 A Comparison Between The Clinical Features Of Pisz And Pizz Patients With Alpha-1 Antitrypsin Deficiency

Introduction Alpha-1 antitrypsin deficiency (AATD) is a hereditary disorder affecting about 1 in 3000 people in the UK commonly associated with early-onset emphysema. There are two common deficiency alleles - PiS and PiZ. PiZZ patients have severe AATD, with levels of 10–15% normal. PiSZ patients have less severe deficiency (≈ 40% normal) and are generally thought to have a minimal risk. We hypothesised that if PiSZ patients were at lower risk of COPD than PiZZ, and their lung disease would be more characteristic of usual COPD than that of PiZZ patients. Method 104 PiSZ patients and 638 PiZZ patients from the UK AATD registry (ADAPT) were compared for their demographics, lung function, risk factors for COPD (e.g. smoking, occupation), co-morbidities associated with COPD, index status (i.e. if diagnosed due to lung disease or family screening) and CT densitometry (where available). Outcome in terms of lung function decline and mortality was also assessed. Univariate statistics were used to guide subsequent regression analyses. Results Emphysema was more likely in PiZZ than PiSZ patients (OR 11.0 (5.7–21.3); p Conclusion PiSZ patients have a milder form of AATD associated with better lung function. The data suggests the pattern of emphysema is closer to usual COPD than classical AATD. Further analyses comparing PiSZ to PiMM are now ongoing.

Emphysema progression is visually detectable in low-dose CT in continuous but not in former smokers.

To evaluate interobserver agreement and time-trend in chest CT assessment of emphysema, airways, and interstitial abnormalities in a lung cancer screening cohort. Visual assessment of baseline and fifth-year examination of 1990 participants was performed independently by two observers. Results were standardised by means of an electronic score sheet; kappa and time-trend analyses were performed. Interobserver agreement was substantial in early emphysema diagnosis; highly significant (p < 0.001) time-trends in both emphysema presence and grading were found (higher prevalence and grade of emphysema in late CT examinations). Significant progression in emphysema was seen in continuous smokers, but not in former smokers. Agreement on centrilobular emphysema subtype was substantial; agreement on paraseptal subtype, moderate. Agreement on panlobular and mixed subtypes was only fair. Agreement was fair regarding airway analysis. Interstitial abnormalities were infrequent in the cohort, and agreement on these was fair to moderate. A highly significant time-trend was found regarding interstitial abnormalities, which were more frequent in late examinations. Visual scoring of chest CT is able to characterise the presence, pattern, and progression of early emphysema. Continuous smokers progress; former smokers do not. • Substantial interobserver consistency in determining early-stage emphysema in low-dose CT. • Longitudinal analyses show clear time-trends for emphysema presence and grading. • For continuous smokers, progression of emphysema was seen in all lung zones. • For former smokers, progression of emphysema was undetectable by visual assessment. • Onset and progression of interstitial abnormalities are visually detectable.

Left Atrial Volume in Chronic Obstructive Pulmonary Disease

The aim of the study was to evaluate left atrial (LA) volume in smokers according to the severity of emphysema, with the objective of providing indirect evidence of reduced pulmonary venous return due to capillary destruction. A total of 121 smokers underwent a high-pitch and high-temporal resolution computed tomography (CT) angiographic examination, enabling quantification of emphysema, total lung volume, and LA volume measurements normalized to body surface area. The CT phenotypes were as follows: emphysema predominant (group 1; n=57); airway predominant (group 2; n=30); a mixed pattern of emphysema and airway disease (group 3; n=15); and absence of bronchopulmonary CT abnormalities (group 4; n=19). A negative correlation was found between the indexed LA volume and the percentage of emphysema: (a) in the overall study group (P=0.032; r=-0.19); (b) in group 1 (P=0.0163; r=-0.32); and (c) in groups 1 and 3 when analyzed together (P=0.0492; r=-0.23). A negative correlation was found between the indexed LA volume and the total lung volume in the overall study group (P=0.039; r=-0.19) and in group 1 (P=0.048; r=-0.26), whereas no correlations were found in group 2 (P=0.44; r=-0.15), group 3 (P=0.52; r=-0.17), and groups 1 and 3 analyzed as a whole (P=0.14; r=-0.17). The indexed LA volume, impacting left ventricular preload, is correlated to the severity of emphysema.

Thoracoscopic-assisted lung lobectomy using hem-o-lok clips in a dog with lung lobe torsion: a case report

An eleven-year-old, 3-kg, intact female Maltese was presented for depression, anorexia and dyspnoea. Thoracic radiographs showed right-side pleural effusion, a vesicular emphysema pattern and consolidation of the right middle lung lobe. A presumptive diagnosis of lung lobe torsion (LLT) in the right middle lobe was made using a computed tomography scan. Thoracoscopic exploration was performed without one-lung ventilation in the right hemithorax. Pleural fluid and engorgement of the torsed lung lobe were observed. A total lung lobectomy of the right middle lung lobe was performed with a thoracoscopic-assisted procedure using hem-o-lok clips applied to the hilus. The dog was discharged three days after surgery, and no recurrence of the clinical signs of disease related to the respiratory system was observed during the follow-up time period of six months. Based on these findings, we conclude that thoracoscopic-assisted lung lobectomy using hem-o-lok clips is a minimally invasive surgical alternative to thoracotomy and successful operative intervention for lung lesions in small breed dogs. &amp;nbsp;

Active relearning for robust supervised training of emphysema patterns.

Radiologists are adept at recognizing the character and extent of lung parenchymal abnormalities in computed tomography (CT) scans. However, the inconsistent differential diagnosis due to subjective aggregation necessitates the exploration of automated classification based on supervised or unsupervised learning. The robustness of supervised learning depends on the training samples. Towards optimizing emphysema classification, we introduce a physician-in-the-loop feedback approach to minimize ambiguity in the selected training samples. An experienced thoracic radiologist selected 412 regions of interest (ROIs) across 15 datasets to represent 124, 129, 139 and 20 training samples of mild, moderate, severe emphysema and normal appearance, respectively. Using multi-view (multiple metrics to capture complementary features) inductive learning, an ensemble of seven un-optimized support vector models (SVM) each based on a specific metric was constructed in less than 6s. The training samples were classified using seven SVM models and consensus labels were created using majority voting. In the active relearning phase, the ensemble-expert label conflicts were resolved by the expert. The efficacy and generality of active relearning feedback was assessed in the optimized parameter space of six general purpose classifiers across the seven dissimilarity metrics. The proposed just-in-time active relearning feedback with un-optimized SVMs yielded 15% increase in classification accuracy and 25% reduction in the number of support vectors. The average improvement in accuracy of six classifiers in their optimized parameter space was 21%. The proposed cooperative feedback method enhances the quality of training samples used to construct automated classification of emphysematous CT scans. Such an approach could lead to substantial improvement in quantification of emphysema.

RANKING AND CLASSIFICATION OF MONOTONIC EMPHYSEMA PATTERNS WITH A MULTI-CLASS HIERARCHICAL APPROACH.

Emphysema has distinct and well-defined visually apparent CT patterns called centrilobular and panlobular emphysema. Existing studies concentrated on the classification of these patterns but they have not looked at the complete evolution of this disease as the destruction of lung parenchyma progresses from normal lung tissue to mild, moderate, and severe disease with complete effacement of the lung architecture. In this paper, we discretize this continuous process into five classes of increasing disease severity and construct a training set of 1161 CT patches. We exploit three solutions to this monotonic multi-class classification problem: a global rankSVM for ranking, hierarchical SVM for classification and a combination of these two, which we call a hierarchical rankSVM. Results showed that both hierarchical approaches were computationally efficient. The classification accuracies were slightly better for hierarchical SVM. However, in addition to classification, ranking approaches also provided a ranking of patterns, which can be utilized as a continuous disease progression score. In terms of the classification accuracy and ratio of pair-wise constraints satisfied, hierarchical rankSVM outperformed the global rankSVM.

Cluster analysis in the COPDGene study identifies subtypes of smokers with distinct patterns of airway disease and emphysema

BackgroundThere is notable heterogeneity in the clinical presentation of patients with COPD. To characterise this heterogeneity, we sought to identify subgroups of smokers by applying cluster analysis to data from...

Progress in Imaging COPD, 2004 - 2014.

Computed tomography (CT) has contributed substantially to our understanding of COPD over the past decade. Visual and quantitative assessments of CT in COPD are complementary. Visual assessment should provide assessment of centrilobular, panlobular and paraseptal emphysema, airway wall thickening, bronchiectasis, findings of respiratory bronchiolitis, and enlargement of the pulmonary artery. Quantitative CT permits evaluation of severity of emphysema, airway wall thickening, and expiratory air trapping, and is now being used for longitudinal evaluation of the progression of COPD. Innovative techniques are being developed to use CT to characterize the pattern of emphysema and smoking- related respiratory bronchiolitis. Magnetic resonance imaging (MRI) and positron emission tomography PET-CT are useful research tools in the evaluation of COPD.