High-resolution CT diagnosis of emphysema in symptomatic patients with normal chest radiographs and isolated low diffusing capacity

Quantitative imaging of COPD

Computed tomography has facilitated recognition that chronic obstructive pulmonary disease is not a single disease but encompasses several overlapping entities, including emphysema, bronchitis, and small airways disease. Quantitative computed tomography can effectively characterize and quantify the extent of emphysema, airway wall thickening, and air trapping related to small airways disease.

Update on radiology of emphysema and therapeutic implications

Emerging treatments require appropriate CT targeting of a selected lobe or lobes and target airways to obtain a successful response. CT scan is used in pretreatment planning to select patients and plan treatment strategy and posttreatment to confirm correct deployment of devices and assess treatment response. Increasingly treatments are being developed to treat patients who have emphysema who require accurate quantitation of extent and distribution of the process. Functional assessment can be made by inference of detailed anatomic correlates and by direct measurement of regional function using dynamic scan protocols. This article summarizes the current role of imaging in the assessment of patients who have emphysema.

Radiological approach to asthma and COPD--the role of computed tomography

Asthma and chronic obstructive pulmonary disease (COPD) are among the most prevalent lung diseases. In both asthma and COPD, airway inflammation leads to airway remodeling. Parenchyma of the lung is also influenced by disease conditions. Airway wall thickening/lumen narrowing and parenchymal destruction occur in COPD. In asthma, airway remodeling contributes to the lung parenchyma. Computed tomography (CT) has been widely used as an imaging tool for lung diseases. With the technical advancement of CT, together with the development of analysis software, it is now possible to analyze the lung parenchymal change and airway remodeling quantitatively using CT. This article reviews the role of CT in assessing the lung structure and functions of patients with asthma and COPD.

Pulmonary perfusion and xenon gas exchange in rats: MR imaging with intravenous injection of hyperpolarized 129Xe

PURPOSE

To develop and demonstrate a method for regional evaluation of pulmonary perfusion and gas exchange based on intravenous injection of hyperpolarized xenon 129 ((129)Xe) and subsequent magnetic resonance (MR) imaging of the gas-phase (129)Xe emerging in the alveolar airspaces.

MATERIALS AND METHODS

Five Fischer 344 rats that weighed 200-425 g were prepared for imaging according to an institutional animal care and use committee-approved protocol. Rats were ventilated, and a 3-F catheter was placed in the jugular (n = 1) or a 24-gauge catheter in the tail (n = 4) vein. Imaging and spectroscopy of gas-phase (129)Xe were performed after injecting 5 mL of half-normal saline saturated with (129)Xe hyperpolarized to 12%. Corresponding ventilation images were obtained during conventional inhalation delivery of hyperpolarized (129)Xe.

RESULTS

Injections of (129)Xe-saturated saline were well tolerated and produced a strong gas-phase (129)Xe signal in the airspaces that resulted from (129)Xe transport through the pulmonary circulation and diffusion across the blood-gas barrier. After a single injection, the emerging (129)Xe gas could be detected separately from (129)Xe remaining in the blood and was imaged with an in-plane resolution of 1 x 1 mm and a signal-to-noise ratio of 25. Images in one rat revealed a matched ventilation-perfusion deficit, while images in another rat showed that xenon gas exchange was temporarily impaired after saline overload, with recovery of function 1 hour later.

CONCLUSION

MR imaging of gas-phase (129)Xe emerging in the pulmonary airspaces after intravenous injection has the potential to become a sensitive and minimally invasive new tool for regional evaluation of pulmonary perfusion and gas exchange.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/2513081550/DC1.

PULMONARY FUNCTION TESTS VERSUS COMPUTED TOMOGRAPHY IN SHEEP WITH EXPERIMENTAL EMPHYSEMA

The authors explored the relative utility of pulmonary function tests (PFTs) and computed tomography (CT) to characterize the progression of papain induced emphysema in sheep (n = 12). PFT included plethysmography (FRC(pleth)), helium dilution (FRC(He)), and expired reserve volume (ERV). Following papain, FRC(pleth) and FRC(He) were unchanged; ERV decreased hence residual volume increased significantly (RV + 270 mL, +86%, P = .02). In contrast, FRC by CT increased in 10 of 12 sheep (+264 mL +21%, P = .008). We conclude that plethysmography was insensitive to emphysema, but the effect on ERV (i.e., trapped gas volume) and FRC by CT were very similar, and in line with the morphologic changes in this animal model.

Imaging in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is divided into pulmonary emphysema and chronic bronchitis (CB). Emphysema is defined patho-anatomically as "permanent enlargement of airspaces distal to the terminal bronchiole, accompanied by the destruction of their walls, and without obvious fibrosis" (1). These lesions are readily identified and quantitated using computed tomography (CT), whereas the accompanying hyperinflation is best detected on plain chest X-ray, especially in advanced disease. The diagnosis of CB is clinical and relies on the presence of productive cough for 3 months in 2 or more successive years. The pathological changes of mucosal inflammation and bronchial wall thickening have been more difficult to identify with available imaging techniques. However, recent studies using Multi-detector row CT (MDCT) reported more reproducible assessment of air wall thickening.

CT quantification of emphysema in young subjects with no recognizable chest disease

OBJECTIVE

The purpose of this prospective study was to evaluate volumetric CT emphysema quantification (CT densitovolumetry) in a young population with no recognizable lung disease.

SUBJECTS AND METHODS

A cohort of 30 nonsmoking patients with no recognizable lung disease (16 men, 14 women; age range, 19-41 years) underwent inspiratory and expiratory CT, after which the data were postprocessed for volumetric quantification of emphysema (threshold, -950 HU). Correlation was tested for age, weight, height, sex, body surface area (BSA), and physical activity. Normal limits were established by mean +/- 1.96 SD.

RESULTS

No correlation was found between the measured volumes and age or physical activity. Correlation was found between BSA and normal lung volume in inspiration (r = 0.69, p = 0.000), shrink volume (i.e., difference in total lung volume in inspiration and in expiration) (r = 0.66, p = 0.000), and percentage of shrink volume (r = 0.35, p = 0.05). For an alpha error of 5%, the limits of normality based on this sample are percentage of emphysema in inspiration, 0.35%; percentage of emphysema in expiration, 0.12%; and maximum lung volume in expiration, 3.6 L. The maximum predicted percentage of shrink volume can be calculated as %SV = 29.43% + 16.97% x BSA (+/- 1.96 x 7.61%).

CONCLUSION

Young healthy nonsmokers with no recognizable lung disease can also show a small proportion of emphysematous-like changes on CT densitovolumetry when a threshold of -950 HU is used. Reference values should be considered when applying the technique for early detection or grading of emphysema and when studying aging lungs.

[Phenotypic heterogeneity of chronic obstructive pulmonary disease]

A functional definition of chronic obstructive pulmonary disease (COPD) based on airflow limitation has largely dominated the field. However, a view has emerged that COPD involves a complex array of cellular, organic, functional, and clinical events, with a growing interest in disentangling the phenotypic heterogeneity of COPD. The present review is based on the opinion of the authors, who have extensive research experience in several aspects of COPD. The starting assumption of the review is that current knowledge on the pathophysiology and clinical features of COPD allows us to classify phenotypic information in terms of the following dimensions: respiratory symptoms and health status, acute exacerbations, lung function, structural changes, local and systemic inflammation, and systemic effects. Twenty-six phenotypic traits were identified and assigned to one of the 6 dimensions. For each dimension, a summary is provided of the best evidence on the relationships among phenotypic traits, in particular among those corresponding to different dimensions, and on the relationship between these traits and relevant events in the natural history of COPD. The information has been organized graphically into a phenotypic matrix where each cell representing a pair of phenotypic traits is linked to relevant references. The information provided has the potential to increase our understanding of the heterogeneity of COPD phenotypes and help us plan future studies on aspects that are as yet unexplored.

Correlation between high-resolution computed tomography features and patients' characteristics in chronic obstructive pulmonary disease

BACKGROUND

During the last few decades, high-resolution computed tomography (HRCT) has come up as a new diagnostic modality to diagnose emphysematous and chronic bronchitis components of chronic obstructive pulmonary disease (COPD). The present study was undertaken to evaluate for various quantitative and qualitative HRCT features in patients with COPD, and to detect patients' characteristics that correlate with these HRCT features.

MATERIALS AND METHODS

Forty male patients with COPD attending the COPD clinic at a tertiary referral hospital and postgraduate medical institute were included in the study. Various HRCT features, including tracheal index, thoracic cage ratio, sterno-aortic distance, thoracic cross-sectional area, vascular attenuation, vascular distortion, mosaic attenuation pattern, and directly visible small airways, were evaluated and correlated with patients' characteristics, including age, duration of illness, quantum of smoking, dyspnea score, quality-of-life index, and various spirometric indices.

RESULTS

We found significant correlations of various quantitative and qualitative HRCT features with age, duration of illness, quantum of smoking, quality-of-life index, and the spirometric indices showing the extent of airways obstruction.

CONCLUSIONS

Various quantitative and qualitative HRCT features were found to correlate with patients' characteristics, spirometric indices, and health-related quality-of-life score, suggesting that HRCT is useful not only in detecting emphysema and its various subtypes but also in predicting the extent and severity of COPD.

Imaging of small airways disease and chronic obstructive pulmonary disease

CT is a useful tool for identification of small airways diseases, and it can be used to classify these entities into inflammatory and constrictive bronchiolitis. Inflammatory forms of bronchiolitis include cellular bronchiolitis (usually caused by infection or aspiration), respiratory bronchiolitis, panbronchiolitis, and follicular bronchiolitis. Constrictive bronchiolitis may be caused by previous infection, toxic inhalation, collagen vascular disease, or transplantation. CT also helps categorize chronic obstructive pulmonary disease into emphysema predominant and airway predominant forms.

Quantitative assessment of emphysema, air trapping, and airway thickening on computed tomography

The severity of chronic obstructive pulmonary disease (COPD) is evaluated not only by airflow limitation but also by factors such as exercise capacity and body mass index. Recent advances in CT technology suggest that it might be a useful tool for evaluating the severity of the disease components of COPD. The aim of this study is to evaluate the correlation between the parameters measured on volumetric CT, including the extent of emphysema, air trapping, and airway thickening, and clinical parameters. CT scans were performed in 34 patients with COPD at full inspiration and expiration. We used in-house software to measure CT parameters, including volume fraction of emphysema (V(950)), mean lung density (MLD), CT air trapping index (CT ATI), segmental bronchial wall area (WA), lumen area (LA), and wall area percent (WA%). We found that the CT parameters were correlated with the pulmonary function test (PFT) results, body mass index (BMI), the modified Medical Research Council Dyspnea scale (MMRC scale), the six-minute-walk distance (6MWD), and the BODE index. V(950 insp) correlated to the BMI, FEV(1), 6MWD, and the BODE index. The CT ATI correlated with the physiologic ATI (VC-FVC) (R=0.345, p=0.045) and the MMRC scale (R=0.532, p=0.001). There was a positive correlation between the WA% and the BMI (R=0.563, p<0.001). MLD(exp) showed the strongest correlation with the BODE index (R= -0.756, p<0.001). We conclude that the severity of emphysema and air trapping measured on CT correlated with the PFT parameters 6MWD and BMI.

High prevalence of emphysema and its association with BMI: a study of smokers with normal spirometry

OBJECTIVES

To evaluate to what extent emphysema was evident, as identified by High Resolution Computed Tomography (HRCT), in smokers with normal lung function and to relate age, gender, smoking history, and body mass index (BMI) to the HRCT results. A secondary aim was to study to what extent emphysema was present in smokers with lower normal values of lung function defined as FEV(1)/FVC ratio percentage of predicted value (89-93% of predicted value for males and 90-93% for females) or FEF(50) < or = 60% of predicted compared with smokers without this definition.

METHODS

Fifty-nine smokers, with a mean age of 53 years and with normal lung function, were examined with HRCT.

RESULTS

Emphysema evidenced visually by HRCT was present in 43% of the subjects. Using a 0-5 grade scale (0=normal finding; 5=emphysema in most slices), the degree of emphysema was almost exclusively 3-4. The type of emphysema was distributed as centrilobular emphysema predominant in 43.5%, paraseptal emphysema predominant in 43.5%, and as an equal mixture of these types in 13%. The presence of emphysema did not differ between the group of smokers with lower normal values of lung function and the rest of the smokers. Smokers with emphysema had significantly lower BMI than those devoid of emphysema, 24 and 27 respectively (p<0.0011).

CONCLUSION

There was a high occurrence of visual emphysema in middle-aged smokers with normal lung function. The densitometric quantitative analysis method is inadequate for detecting mild emphysema. High prevalence of emphysema was associated with low BMI.

Chronic effort dyspnea explained by lung function tests and by HRCT and CRX radiographic patterns in COPD: a post-hoc analysis in 51 patients

This paper is a post-hoc analysis of a previous study performed to investigate the relationship between computerized tomography (CT) and lung function in 51 outpatients with mild-to-moderate COPD. We studied whether changes in lung function and radiographic patterns may help to explain dyspnea, the most disturbing symptom in patients with COPD. The Medical Research Council (MRC) dyspnea scale shows, by univariate analysis, a similar strength of association to CT expiratory lung density and to DL(CO), a functional index of lung parenchymal loss. The MRC dyspnea scale shows a somewhat less strength of association with a small vertical heart on plain chest films. In multivariate analysis, the model with the strongest association to the MRC dyspnea scale (r = 0.76, p < 0.0001) contains 4 explanatory variables (DL(CO), FRC, PaCO(2), and radiographic pattern of pulmonary hypertension). We suggest that diffusing capacity reflects the emphysematous component of hyperinflation, associated by definition with destruction of terminal airspace walls, as distinct from the air trapping component, which is ascribed to airway obstruction and associated with FRC. PaCO(2) mainly reflects the ventilatory components, i.e., ventilatory drive and ventilatory constraints, of pulmonary gas exchange in COPD, while radiographic pattern of pulmonary hypertension likely reflects hypoxic vascular changes, which depend mainly on ventilation/perfusion mismatch and give rise to pulmonary arterial hypertension that may contribute per se to dyspnea. In conclusion, our analysis points out that chronic effort dyspnea variance may account for up to 58% (r(2) = 0.58) by lung function tests and radiographic patterns. Thus, about 42% of the MRC dyspnea variance remains unexplained by this model. On the other hand, dyspnea ascertainment is dependent on subjective behavior and evaluation and in tests is influenced by individual performance and perception. For example in the 6-minute walk test, a similar or higher proportion (60%) of the overall variance is unexplained.

Phenotypes of chronic obstructive pulmonary disease

The current clinical classification of smoking-related lung disease fails to take into account the heterogeneity of chronic obstructive pulmonary disease (COPD). With an increased understanding of pathophysiologic variation, COPD now clearly represents a spectrum of overlapping diseases with important extrapulmonary consequences. A "phenotype" describes the outward physical manifestations of a particular disease, and compromises anything that is part of the observable structure, function or behavior of an individual. Such phenotypic distinctions in COPD include: frequent exacerbator, pulmonary cachectic, rapid decliner, airways hyperresponsiveness, impaired exercise tolerance, and emphysema versus airways disease. These variable manifestations, each with unique prognostic, clinical and physiologic ramifications, represent distinct phenotypes within COPD. While all of these phenotypes have smoking as a common risk factor, the other risk factors that determine these phenotypes remain poorly understood. An individual smoker has variable expression of each phenotype and there is mounting evidence that COPD phenotypes have different clinical outcomes. These phenotypes can be broadly classified into one of three groups: clinical, physiologic and radiographic. This review presents the evidence for the spectrum of COPD phenotypes with a focused discussion on the pathophysiologic, epidemiologic and clinical significance of each subtype.

Radiologic and Clinical Features of COPD Patients With Discordant Pulmonary Physiology

INTRODUCTION

Subjects with COPD display heterogeneity in clinical, physiologic, and radiologic characteristics, which are thought to result from different pathophysiologic mechanisms. It is important to identify and understand specific phenotypes for patient management. We investigated differences in emphysema distribution and health status in alpha(1)-antitrypsin deficient subjects (PiZ) with discordant lung function.

METHOD

CT scan densitometry, arterial oxygen tension, and St. George respiratory questionnaire scores were compared for 15 subjects with normal FEV1 and lung diffusion capacity corrected for alveolar ventilation (KCO), both defined as > 80% predicted (group 1), 10 subjects with abnormal FEV(1) and normal KCO (group 2), 15 subjects with normal FEV1 and abnormal KCO (group 3), and 10 subjects with both an abnormal FEV1 and KCO (group 4).

RESULTS

Group 2 subjects had the greatest predominance of basal emphysema, and group 3 subjects had the least. Upper zone voxel index (ie, the percentage of voxels < -910 Hounsfield units) was greater in all groups with abnormal lung function (p = 0.003, 0.044, and < 0.001, respectively), indicating more upper zone emphysema than in subjects with normal lung function. Lower zone voxel index was increased in groups 2 and 4 compared to groups 1 and 3. Groups 2 and 4 had a lower Pao(2) (p < 0.001) than the other groups. All groups with abnormal lung function had a worse quality of life than those with normal lung function.

CONCLUSION

Abnormality of FEV1 is associated with basal-predominant emphysema, and abnormality of KCO is associated with relatively more upper zone emphysema; but, an isolated defect in KCO has a significant effect on health status.

Associations between reduced diffusing capacity and airflow obstruction in community-based subjects

INTRODUCTION

The purpose of this analysis was to determine if abnormal diffusing capacity of the lung for carbon monoxide (DLco) identified a group of subjects with significantly different characteristics than those with normal lung function or airflow obstruction alone.

METHODS

Participants were a random sample of adults aged 45-70 years. They completed a detailed respiratory questionnaire, spirometry, methacholine challenge and measurement of single breath DLco. Subjects were categorized into one of three groups: airflow obstruction only, reduced DLco only, or both airflow obstruction and reduced DLco.

RESULTS

Individuals with airflow obstruction and reduced DLco in combination reported more symptoms than those with either condition alone. In subjects with a combination of both airflow obstruction and reduced DLco, a significantly higher proportion reported use of medication and laboratory tests. Current smoking was significantly associated with a reduced DLco alone and in combination with airflow obstruction, however, the association was stronger in those with DLco and airflow obstruction. Bronchial hyperreactivity (BHR) was found to be a risk factor while atopy was associated with a reduced risk of DLco and airflow obstruction.

CONCLUSIONS

Reduced DLco plus airflow obstruction together identifies a group of individuals with significantly more symptoms and worse lung function. Current cigarette smoking, early life serious respiratory infection and BHR were strongly associated with reduced DLco in combination with airflow obstruction.

Retrospective study of pulmonary function tests in patients presenting with isolated reduction in single-breath diffusion capacity: implications for the diagnosis of combined obstructive and restrictive lung disease

OBJECTIVE

To examine the frequency and spectrum of diseases associated with isolated reduction in the diffusing capacity of lung for carbon monoxide (D(Lco)).

PATIENTS AND METHODS

We retrospectively identified all potentially dyspneic patients who had pulmonary function tests (PFTs) performed at the Mayo Clinic in Jacksonville, Fla, between January 1, 1990, and June 30, 2000, that showed reduced D(Lco) (< 70% of predicted), normal lung volumes (total lung capacity and residual volume > 80% and < 120% of predicted, respectively), and airflow variables (forced expiratory volume in 1 second and forced vital capacity values > 80% of predicted and forced expiratory volume in 1 second/forced vital capacity ratio > 70% of predicted). Only patients who had also undergone chest computed tomography (CT) and echocardiography within 1 month of PFTs were studied.

RESULTS

Of the 38,095 patients who underwent PFTs during the study period, 179 (0.47%; 95% confidence interval [CI], 0.40%-0.54%) had isolated D(Lco) abnormalities. The 27 patients (15.1%; 95% CI, 10.2%-21.2%) who had also undergone chest CT and echocardiography within 1 month of PFTs form the study cohort reported herein. Their mean D(Lco) was 50% +/- 15% (95% CI, 45%-56%) with average normal pulse oxygen saturation at rest and mild hypoxemia with activity. Thirteen of the 27 patients (48%; 95% CI, 28.7%-68.1%) had underlying emphysema evident on CT. Eleven of these 13 patients had emphysema associated with a restrictive lung process. The 14 patients without emphysema had interstitial lung disease, pulmonary vascular disease, and other isolated findings. Six patients with combined emphysema and idiopathic pulmonary fibrosis accounted for the largest percentage (22%) of patients with Isolated D(Lco) reduction. The mean +/- SD smoking history of the 27 patients in the study cohort was 36 +/- 33 pack-years (range, 0-116 pack-years).

CONCLUSION

Dyspneic patients with respiratory symptoms and normal lung volumes and airflows associated with Isolated reduction in D(Lco) should be evaluated for underlying diseases such as emphysema, with or without a concomitant restrictive process, and pulmonary vascular disease.

Quantification of emphysema: a composite physiologic index derived from CT estimation of disease extent

The combination of functional indices best reflecting the extent of emphysema is not known. High-resolution computed tomography (HRCT) studies of 106 patients with emphysema [men=71; median age=61 (range=26-86 years)] were reviewed and the extent of emphysema was quantified: (a) visually (emphysema(vis)) and (b) by automated estimation (emphysema(auto)). Functional-morphologic relationships were compared for the two scoring systems, and a composite physiologic index (CPI) (providing the best fit of functional indices against emphysema extent) was derived. Emphysema(vis) and emphysema(auto) were strongly correlated (r=0.90; p<0.0005), but the extent of emphysema(vis) was consistently greater (p<0.00005). Emphysema(vis) correlated most strongly with indices of gas transfer [percent predicted single-breath carbon monoxide diffusing capacity (Dl(co)) and alveolar volume (K(co)); r=-0.70, both p<0.0005]. The combination of physiologic indices most representative of emphysema extent on CT (using visual or automated methods) consisted of K(co) and forced expiratory volume in 1 s (FEV(1)) levels. The equation explanatory power was higher for visual scoring [emphysema(vis)=96.8-(0.67 x % predicted K(co))-(0.41 x % predicted FEV(1)); equation r(2)=0.57] than automated estimation (equation r(2)=0.48). Weighted combinations of K(co) and FEV(1) levels provide a CPI best reflecting morphologic emphysema extent. CPI has the potential to refine the stratification of patients in epidemiological and therapeutic studies.

State of the Art. A structural and functional assessment of the lung via multidetector-row computed tomography: phenotyping chronic obstructive pulmonary disease

With advances in multidetector-row computed tomography (MDCT), it is now possible to image the lung in 10 s or less and accurately extract the lungs, lobes, and airway tree to the fifth- through seventh-generation bronchi and to regionally characterize lung density, texture, ventilation, and perfusion. These methods are now being used to phenotype the lung in health and disease and to gain insights into the etiology of pathologic processes. This article outlines the application of these methodologies with specific emphasis on chronic obstructive pulmonary disease. We demonstrate the use of our methods for assessing regional ventilation and perfusion and demonstrate early data that show, in a sheep model, a regionally intact hypoxic pulmonary vasoconstrictor (HPV) response with an apparent inhibition of HPV regionally in the presence of inflammation. We present the hypothesis that, in subjects with pulmonary emphysema, one major contributing factor leading to parenchymal destruction is the lack of a regional blunting of HPV when the regional hypoxia is related to regional inflammatory events (bronchiolitis or alveolar flooding). If maintaining adequate blood flow to inflamed lung regions is critical to the nondestructive resolution of inflammatory events, the pathologic condition whereby HPV is sustained in regions of inflammation would likely have its greatest effect in the lung apices where blood flow is already reduced in the upright body posture.

Functional impairment in emphysema: contribution of airway abnormalities and distribution of parenchymal disease

OBJECTIVE

The aim of this study was to identify ancillary morphologic features on high-resolution CT that modify airflow obstruction and gas transfer levels in individuals with emphysema.

MATERIALS AND METHODS

The extent of emphysema on high-resolution CT was quantified by density masking in 101 patients. CT scans were evaluated for airway abnormalities (bronchial wall thickness, extent of bronchiectasis, bronchial dilatation, and evidence of small airways disease) and disease heterogeneity (uniformity, core-rind distribution, craniocaudal distribution, and lung texture). Stepwise regression analysis was used to determine CT features that influenced forced expiratory volume in 1 sec (FEV1) and the single-breath diffusing capacity for carbon monoxide (Dlco) for a given extent of emphysema.

RESULTS

The extent of emphysema using automated estimation was 28.4% +/- 12.3% (mean +/- SD). On univariate analysis the extent of emphysema correlated strongly with FEV1 (R = -0.63, p < 0.0005) and Dlco (R = -0.63, p < 0.0005) levels. Stepwise regression analysis revealed that bronchial wall thickness and the extent of emphysema were the strongest independent determinants of FEV1 (model R2 = 0.49; p = 0.002 and < 0.001, respectively); the extent of bronchiectasis and degree of bronchial dilation did not separately influence FEV1 levels. The only morphologic features linked to Dlco levels on multivariate analysis were increasingly extensive emphysema and a higher proportion of emphysema in the core region (model R2 = 0.45; p < 0.001 and 0.002, respectively).

CONCLUSION

The important additional CT abnormalities in individuals with emphysema that influence FEV1 and Dlco levels irrespective of disease extent are bronchial wall thickness and core-rind heterogeneity, respectively. These observations have implications for the accurate functional assessment of patients considered for lung volume reduction surgery.

Emphysematous changes and normal variation in smokers and COPD patients using diffusion 3He MRI

INTRODUCTION

This study aims to quantify global and regional changes of diffusive motion of 3He gas within the lung, as determined by hyperpolarized 3He MR apparent diffusion coefficient (ADC) measurement, in non-smokers, smokers and chronic obstructive pulmonary disease (COPD) patients.

METHODS

Age-matched groups of six healthy non-smokers, five healthy smokers and five patients with COPD. The experiments were performed with approval from the local Research Ethics Committee. Diffusion imaging was performed following hyperpolarized 3He gas inhalation, producing ADC maps. Mean and standard deviation of the ADCs were used to compare the subject groups and assess regional variations within individuals.

RESULTS

The intra-individual standard deviation of ADC in the healthy smokers was significantly larger than that of the non-smoking group (P < 0.02). Compared to the non-smoking group, COPD patients had significantly higher mean and standard deviation of ADC (P < 0.01). The mean ADC in the anterior half of the chest was systematically higher than in the posterior half in the healthy non-smoking subject group.

DISCUSSION

This study suggests that there are regional trends in the ADC values of healthy volunteers that may have implications for the clinical interpretation of ADC values. Less homogeneous ADC values have been detected in asymptomatic smokers, indicative of damage to the distal air spaces.

Alpha1-antitrypsin deficiency. 7: Computed tomographic imaging in alpha1-antitrypsin deficiency

Computed tomographic scanning may replace lung function tests as the golden standard for assessing the response to known and novel treatments for alpha1-antitrypsin deficiency.

Pattern of emphysema distribution in alpha1-antitrypsin deficiency influences lung function impairment

FEV(1) is fundamental to the diagnosis and staging of chronic obstructive pulmonary disease. In emphysema, airflow obstruction usually coexists with impairment of gas exchange, but discordance is not infrequent. We hypothesized that variations in the distribution of emphysema would be associated with functional differences and therefore account for discordant physiology. We used quantitative computed tomography to assess emphysema severity and distribution in 119 subjects with alpha1-antitrypsin deficiency (PiZ phenotype) and grouped them according to distribution pattern. In the 102 subjects with emphysema, 65 had a predominantly basal pattern ("basal"), but 37 (36%) had greater involvement of the upper regions ("apical"). Subjects from each group were matched for total volume of emphysema and age, and matched pairs analysis was used to relate emphysema distribution to clinical phenotype. Basal distribution was associated with greater impairment of FEV(1) (mean difference, 9.9% predicted; 95% confidence interval, 3.8 to 16.0; p = 0.002) but less impairment of gas exchange (Pa(O(2)) mean difference, 0.5 kPa, 0.03 to 0.1; p = 0.016) and alveolar-arterial oxygen gradient (mean difference, 0.7 kPa; 0.2 to 1.2; p = 0.007) than the apical distribution. Emphysema distribution correlated with physiologic discordance (r = -0.409, p < 0.001). The use of single physiologic parameters as a surrogate measure of emphysema severity may introduce systematic bias in the staging of subjects with emphysema.

Long-term sequelae of Farmer's lung disease in HRCT: a 14-year follow-up study of 88 patients and 83 matched control farmers

The aim of this study was to compare high-resolution computed tomography (HRCT) findings of long-term farmer's lung (FL) patients and control farmers. We studied 88 FL patients and 83 matched control farmers with a mean follow-up time of 14 years. Emphysematous, fibrotic, and miliary changes were recorded by HRCT. The pattern of emphysema and location and distribution of other findings were evaluated in detail. Emphysema was found in 20 (23%) FL patients and in 6 (7%) controls (p=0.005). Recurrences of FL attacks increased (p=0.021) the risk of emphysema. Prevalence of fibrosis (17 vs 10%, p=0.16) and miliary changes (11 vs 4%, p=0.06) did not differ significantly in patients and controls. Among FL patients, emphysematous, fibrous, and miliary changes were more pronounced at the base than in the upper parts of the lung (p<0.02). In slice analysis, the pattern of emphysema was more polymorphous (p=0.001) and the distribution of fibrotic and miliary changes was more variable among FL patients than controls. Emphysema in HRCT is more common in FL patients than matched control farmers, and the occurrence is increased by recurrences of FL. Emphysematous, fibrous, and miliary changes in FL patients HRCT are multiform and predominate in the lower parts of the lung.

Chronic obstructive pulmonary disease. 4: imaging the lungs in patients with chronic obstructive pulmonary disease

The role of chest radiography and computed tomography in the evaluation of pulmonary emphysema and chronic bronchitis is reviewed.

Low-density areas on high-resolution computed tomograms in chronic pediatric asthma

OBJECTIVE

In children with chronic persistent asthma, we evaluated whether the presence of increased residual volume (RV) after anti-inflammatory treatment correlates with the detection of low-density areas on high-resolution computed tomography (HRCT), similar to those in emphysema.

METHODS

Children with a confirmed diagnosis of asthma (n = 32) were enrolled in a prospective study. All patients had reduction of airflow in the peripheral airways, increased RV, and increased serum eosinophil cationic protein (ECP) values indicating airway inflammation. All the children were treated with salmeterol (50 microg twice daily) and fluticasone (250 microg twice daily) for a 3-month period.

RESULTS

At the end of treatment, peripheral eosinophil counts, serum ECP, forced expiratory volume in 1 second (FEV(1)), mean forced expiratory flow during the middle half of forced vital capacity (FEF(25-75)), RV, and total lung capacity values improved in all the patients. HRCT was normal in 22 children (68.8%); in the remaining 10 subjects, low-density areas were found despite normalization of FEV(1), FEF(25-75), and significant reduction in ECP. A significant correlation was found between persistence of RV values >150% predicted and the presence of low-density areas on HRCT (r = 0.84, P <.0001).

CONCLUSIONS

Structural changes similar to emphysema are also present in asthmatic children. Our findings suggest that the persistence of increased RV may be used to identify subjects with low-density areas on HRCT.

Thin-section CT in obstructive pulmonary disease: discriminatory value

PURPOSE

To use thin-section computed tomography (CT) to distinguish between causes of obstructive pulmonary disease, to determine which distinctions give rise to diagnostic imprecision, and to identify the most useful CT features.

MATERIALS AND METHODS

Thin-section CT scans of 105 patients with obstructive pulmonary disease (asthma, n = 35; centrilobular emphysema, n = 30; panlobular emphysema, n = 21; and obliterative bronchiolitis, n = 19) and 33 healthy subjects were assessed independently by two observers. The most likely diagnosis and a confidence rating were assigned. Individual thin-section CT features were recorded. Accuracy, sensitivity, specificity, negative predictive value, and positive predictive value for first-choice diagnoses were calculated. The prevalence of CT features between pairs of conditions was compared with the chi(2) or Fisher exact test as appropriate.

RESULTS

A correct first-choice diagnosis was made in 199 of 276 (72%) observations. A correct first-choice diagnosis was made in 35 of 38 (92%) observations in patients with obliterative bronchiolitis, in 53 of 60 (88%) observations in patients with centrilobular emphysema, in 53 of 66 (80%) observations in healthy subjects, in 37 of 70 (53%) observations in patients with asthma, and in 20 of 42 (48%) observations in patients with panlobular emphysema. The major sources of diagnostic inaccuracy were differentiation between panlobular and centrilobular emphysema, asthma and normality, and asthma and obliterative bronchiolitis. There were significant increases in prevalence of (a) bronchial wall thickening and vascular attenuation in patients with asthma when compared with healthy subjects and (b) vascular attenuation and decreased attenuation in patients with obliterative bronchiolitis when compared with patients with asthma (P <.001).

CONCLUSION

CT helps to distinguish diseases that cause airflow obstruction. Thin-section CT is particularly accurate in the identification of obliterative bronchiolitis.

Longitudinal follow-up study of smoker's lung with thin-section CT in correlation with pulmonary function tests

PURPOSE

To evaluate thin-section computed tomography (CT) in depicting longitudinal changes in the lung parenchyma.

MATERIALS AND METHODS

One hundred eleven volunteers underwent sequential examination with thin-section CT and pulmonary function tests over a mean period of 5.5 years. According to their smoking habits between initial evaluation (T0) and follow-up (T1), the subjects were classified as persistent current smokers (n = 57), persistent nonsmokers (n = 31), persistent ex-smokers (n = 13), or quitters (n = 10).

RESULTS

Significant differences in CT findings between T0 and T1 were seen in only the group of persistent current smokers, who showed a higher frequency of emphysema (40% vs 26%; P =.005) and ground-glass attenuation (42% vs 28%; P =.02). Individual analysis of follow-up CT scans in the 19 persistent current smokers with micronodules at T0 demonstrated (a) no changes in seven cases, (b) a higher profusion of micronodules in seven cases, and (c) replacement of micronodules with emphysema in five cases. Subjects with emphysema and/or areas of ground-glass attenuation at T0 had a significantly more rapid decline in lung function than did those with a normal CT scan.

CONCLUSION

Emphysema and/or ground-glass attenuation are linked with impairment of ventilatory lung function over time in persistent current smokers.

CT of emphysema

This article focuses on three main topics: (1) the importance of emphysema as a serious respiratory disease, (2) qualitative assessment of emphysema using CT, and (3) the emerging importance of quantitative CT in the evaluation of patients with emphysema for surgery and drug therapy. CT also can identify the major anatomic subtypes of emphysema. CT is critical in the assessment of patients with the potential for lung volume reduction surgery. CT may well be superior to pulmonary function tests in the longitudinal assessment of current and proposed drug therapies for the treatment of emphysema.

Patterns of lung disease in a "normal" smoking population: are emphysema and airflow obstruction found together?

STUDY OBJECTIVES

We determined whether emphysema demonstrated on high-resolution CT (HRCT) scanning in apparently well smokers is associated with airflow obstruction.

INTERVENTIONS

Lung function testing and limited HRCT scanning.

DESIGN

Lung function measurements and scans were analyzed independently of each other. We used analysis of covariance to compare FEV(1) and maximum expiratory flow at 50% of vital capacity (MEF(50)) values after suitable corrections, between subjects with and without parenchymal damage (emphysema and/or reduced carbon monoxide transfer coefficient [KCO]), and to compare indexes of parenchymal damage between subjects with and without airflow obstruction.

SETTING

Radiology and lung function departments of a district general hospital.

PARTICIPANTS

Eighty current cigarette smokers and 20 lifetime nonsmoking control subjects (aged 35 to 65 years) who volunteered following publicity in local media. In all subjects, FEV(1) was > 1.5 L; no subjects were known to have lung disease.

MEASUREMENTS AND RESULTS

FEV(1) and MEF(50) were measured spirometrically; static lung volumes were measured by helium dilution and body plethysmography; KCO was measured by a single-breath technique. HRCT scans were analyzed for emphysema by two radiologists. Of smokers, 25% had HRCT emphysema, generally mild; 16.3% and 25% had reduced FEV(1) and MEF(50), respectively; 12.5% had reduced KCO. Smokers with airflow obstruction were not more likely to have parenchymal damage. Smokers with parenchymal damage did not have reduced airway function. Nonsmokers generally had normal airways and parenchyma.

CONCLUSIONS

"Normal" smokers with lung damage had either airflow obstruction or parenchymal damage, but not generally both.

Assessment of lung volumes in pulmonary emphysema using multidetector helical CT: comparison with pulmonary function tests

The purpose of this study is to evaluate the usefulness of multidetector helical CT (MDCT) with three-dimensional (3D) postprocessing for assessing the lung volume at inspiration and expiration of the pulmonary emphysema and for comparing it with pulmonary function tests. Percentage lung volume at the threshold of -930, -900, -810, -790, and -770 at expiration showed good correlation with FEV1, FEV1/FVC, and DLCO/Va. Excellent correlation was observed between percentage lung volume at the threshold of -900 and FEV1/FVC. CT densitometry at expiration showed better correlation than that at inspiration with pulmonary function tests. MDCT with 3D technique is useful for assessing the severity of pulmonary emphysema.

Dyspnoea in the elderly: a clinical approach to diagnosis

This review briefly overviews the pathophysiology of dyspnoea and then focuses on discussion of the most frequent causes of chronic and acute dyspnoea in the elderly. The most common causes of dyspnoea in the elderly include heart failure, chronic obstructive pulmonary disease and asthma. Other causes include parenchymal lung disease, pulmonary vascular diseases, upper airway obstruction and pneumonia. Dyspnoea should not be attributed to aging alone. Careful clinical evaluation and spirometry is indicated, and additional testing may be appropriate. In this article, emphasis is placed on the clinical manifestations of dyspnoea in the elderly and an approach to their differential diagnosis is provided. Discussion of available therapy is beyond the scope of this article.

Estudo comparativo entre tomografia computadorizada de alta resolução e radiografia de tórax no diagnóstico da silicose em casos incipientes

Introdução:A radiografia de tórax (RX) ainda é, no dias atuais, o principal método de diagnóstico da silicose, seguindo-se as normas da Organização Internacional do Trabalho (OIT). A interpretação radiológica de casos iniciais é difícil, podendo ocorrer divergências mesmo entre leitores experientes. Recentemente, tem sido considerada a possibilidade de utilização da tomografia computadorizada com técnica de alta resolução (TCAR) para avaliação de casos incipientes. Objetivo: Comparar os resultados da RX com a TCAR. Material e métodos: Foi avaliado um grupo inicial de 135 ex-mineiros, cujas radiografias foram examinadas por três leitores, no período de novembro de 1997 a dezembro de 1999. Indicou-se TCAR para 68 pacientes, cuja mediana de três leituras radiológicas foi menor ou igual a 1/0. As tomografias foram avaliadas por dois leitores e, em casos de divergência, houve participação de um terceiro leitor. As TCAR foram classificadas de acordo com a profusão de micronódulos em categorias de 0 a 3. Os resultados de TCAR e RX foram comparados através do teste de McNemar, coeficiente Kappa ponderado e modelos log-lineares. Resultados e conclusão: Houve boa concordância entre os métodos quanto à classificação na categoria 0, ou seja, os dois métodos mostraram-se equivalentes para excluir o diagnóstico de silicose. Porém, para o diagnóstico da doença, caracterizado por classificação na categoria 1 ou superior, não foi obtida boa concordância entre os métodos.

High-resolution computed tomography scanning in alpha1-antitrypsin deficiency: relationship to lung function and health status

The development of computed tomography (CT) has enabled emphysema to be assessed noninvasively. Objective quantification of lung density correlates well with lung function in patients with chronic obstructive pulmonary disease and has been shown to be a sensitive tool for monitoring disease progression. In order to determine the clinical impact of changes seen on high-resolution computed tomography (HRCT), the relationship between the objective quantification of emphysema on HRCT, lung function and health status in 111 patients with alpha1-antitrypsin deficiency was examined (PiZ). The degree of HRCT scan abnormality correlated well (p<0.001 for all comparisons) with forced expiratory volume in one second (r = -0.60- -0.75), specific airway conductance (r = -0.67-0.76), residual volume/total lung capacity (r = 0.46-0.58) and transfer factor of the lung for carbon monoxide (r = -0.64- -0.81). In addition, the CT scans correlated (p<0.001) with health status as assessed by the St. George's Respiratory Questionnaire (SGRQ total: r = -0.38-0.50) and the Short-Form health survey (e.g. physical functioning: r = -0.39-0.54). In summary, other workers have shown high-resolution computed tomography to be a sensitive indicator of disease progression. This study confirms the relationship between high-resolution computed tomography and lung physiology, and suggests the relationship is even stronger in patients with predominantly lower zone pan-lobular emphysema than in usual chronic obstructive pulmonary disease. High-resolution computed tomography also relates to patients disability and impairment as defined by health status questionnaires and, therefore, should be considered as an alternative outcome measure particularly in alpha1-antitrypsin deficiency.

Automated CT image evaluation of the lung: a morphology-based concept

Computed tomography (CT) provides the most reliable method to detect emphysema in vivo. Commonly used methods only calculate the area of low attenuation [pixel index (PI)], while a radiologist considers the bullous morphology of emphysema. The PI is a good, well-known measure of emphysema. But it is not able to detect emphysema in cases in which emphysema and fibrosis occur at the same time. This is because fibrosis leads to a low number of low-attenuation pixels, while emphysema leads to a high number of pixels. The PI takes the average of both and, consequently, may present a result within the normal range.

METHOD

The main focus of this paper is to present a new algorithm of thoracic CT image evaluation based on pulmonary morphology of emphysema. The PI is extended, in that it is enabled to differentiate between small, medium, and large bullae (continuous low-attenuation areas). It is not a texture-based algorithm. The bullae are sorted by size into four size classes: class 1 being within the typical size of lung parenchyma; classes 2-4 presenting small, medium, and large bullae. It is calculated how much area the different classes take up of all low-attenuation pixels. The bullae index (BI) is derived from the percentage of areas covered, respectively, by small, medium, and large bullae. From the relation of the area of bullae belonging to class 4, to that of those belonging to class 2, a measure of the emphysema type (ET)is calculated. It classifies the lung by the type of emphysema in bullous emphysema or small-sized, diffuse emphysema, respectively.

RESULTS

The BI is as reliable as the PI. In cases in which the PI indicates normal values while in fact emphysema is coexisting with fibrosis, the BI, nevertheless, detects the destruction caused by the emphysema. The BI combined with the ET reflects the visual assessment of the radiological expert.

CONCLUSION

The BI is an objective and reliable index in order to quantify emphysematous destruction, hence, avoiding interobserver variance. This is particularly interesting for follow-up. The classification of the ET is a helpful and unique approach to achieving an exact diagnosis of emphysema.

Advances in radiologic assessment of chronic obstructive pulmonary disease

Chest radiography allows detection of moderate and severe emphysema but does not allow quantitation of severity of disease or detection of mild emphysema. Chest radiography is helpful in assessing complications of emphysema such as pneumothorax or secondary infection of a bulla. HRCT provides a detailed image of emphysematous lung disease comparable to that of macroscopic pathologic appearance. The main role of HRCT in patients with COPD is in the preoperative assessment of patients being considered for bullectomy or LVRS.