Preoperative severity of emphysema predictive of improvement after lung volume reduction surgery: use of CT morphometry

Application of 3D computed tomography in emphysematous parenchyma patients scheduled for bronchoscopic lung volume reduction

Bronchoscopic lung volume reduction (BLVR) is a feasible, safe, effective and minimally invasive technique to significantly improve the quality of life of advanced severe chronic obstructive pulmonary disease (COPD). In this study, three-dimensional computed tomography (3D-CT) automatic analysis software combined with pulmonary function test (PFT) was used to retrospectively evaluate the postoperative efficacy of BLVR patients. The purpose is to evaluate the improvement of lung function of local lung tissue after operation, maximize the benefits of patients, and facilitate BLVR in the treatment of patients with advanced COPD. All the reported cases of advanced COPD patients treated with BLVR with one-way valve were collected and analysed from 2017 to 2020. Three-dimensional-CT image analysis software system was used to analyse the distribution of low-density areas <950 Hounsfield units in both lungs pre- and post- BLVR. Meanwhile, all patients performed standard PFT pre- and post-operation for retrospective analysis. We reported six patients that underwent unilateral BLVR with 1 to 3 valves according to the range of emphysema. All patients showed a median increase in forced expiratory volume in 1 second (FEV1) of 34%, compared with baseline values. Hyperinflation was reduced by 16.6% (range, 4.9%-47.2%). The volumetric measurements showed a significant reduction in the treated lobe volume among these patients. Meanwhile, the targeted lobe volume changes were inversely correlated with change in FEV1/FEV1% in patients with heterogeneous emphysematous. We confirm that 3D-CT analysis can quantify the changes of lung volume, ventilation and perfusion, to accurately evaluate the distribution and improvement of emphysema and rely less on the observer.

Pulmonary functional MRI: Detecting the structure-function pathologies that drive asthma symptoms and quality of life

Pulmonary functional MRI (PfMRI) using inhaled hyperpolarized, radiation-free gases (such as ³ He and ¹²⁹ Xe) provides a way to directly visualize inhaled gas distribution and ventilation defects (or ventilation heterogeneity) in real time with high spatial (~mm³ ) resolution. Both gases enable quantitative measurement of terminal airway morphology, while ¹²⁹ Xe uniquely enables imaging the transfer of inhaled gas across the alveolar-capillary tissue barrier to the red blood cells. In patients with asthma, PfMRI abnormalities have been shown to reflect airway smooth muscle dysfunction, airway inflammation and remodelling, luminal occlusions and airway pruning. The method is rapid (8-15 s), cost-effective (~$300/scan) and very well tolerated in patients, even in those who are very young or very ill, because unlike computed tomography (CT), positron emission tomography and single-photon emission CT, there is no ionizing radiation and the examination takes only a few seconds. However, PfMRI is not without limitations, which include the requirement of complex image analysis, specialized equipment and additional training and quality control. We provide an overview of the three main applications of hyperpolarized noble gas MRI in asthma research including: (1) inhaled gas distribution or ventilation imaging, (2) alveolar microstructure and finally (3) gas transfer into the alveolar-capillary tissue space and from the tissue barrier into red blood cells in the pulmonary microvasculature. We highlight the evidence that supports a deeper understanding of the mechanisms of asthma worsening over time and the pathologies responsible for symptoms and disease control. We conclude with a summary of approaches that have the potential for integration into clinical workflows and that may be used to guide personalized treatment planning.

Treating tumors with minimally invasive therapy: A review

With high level of morbidity and mortality, tumor is one of the deadliest diseases worldwide. Aiming to tackle tumor, researchers have developed a lot of strategies. Among these strategies, the minimally invasive therapy (MIT) is very promising, for its capability of targeting tumor cells and resulting in a small incision or no incisions. In this review, we will first illustrate some mechanisms and characteristics of tumor metastasis from the primary tumor to the secondary tumor foci. Then, we will briefly introduce the history, characteristics, and advantages of some of the MITs. Finally, emphasis will be, respectively, focused on an overview of the state-of-the-art of the HIFU-, PDT-, PTT-and SDT-based anti-tumor strategies on each stage of tumor metastasis.

Associations of airway tree to lung volume ratio on computed tomography with lung function and symptoms in chronic obstructive pulmonary disease

Background

Decreased airway lumen size and increased lung volume are major structural changes in chronic obstructive pulmonary disease (COPD). However, even though the outer wall of the airways is connected with lung parenchyma and the mechanical properties of the parenchyma affect the behaviour of the airways, little is known about the interactions between airway and lung sizes on lung function and symptoms. The present study examined these effects by establishing a novel computed tomography (CT) index, namely, airway volume percent (AWV%), which was defined as a percentage ratio of the airway tree to lung volume.

Methods

Inspiratory chest CT, pulmonary function, and COPD Assessment Tests (CAT) were analysed in 147 stable males with COPD. The whole airway tree was automatically segmented, and the percentage ratio of the airway tree volume in the right upper and middle-lower lobes to right lung volume was calculated as the AWV% for right lung. Low attenuation volume % (LAV%), total airway count (TAC), luminal area (Ai), and wall area percent (WA%) were also measured.

Results

AWV% decreased as the Global Initiative for Chronic Obstructive Lung Disease (GOLD) spirometric grade increased (p < 0.0001). AWV% was lower in symptomatic (CAT score ≥ 10) subjects than in non-symptomatic subjects (p = 0.036). AWV% was more closely correlated with forced expiratory volume in 1 s (FEV₁) and ratio of residual volume to total lung capacity (RV/TLC) than Ai, Ai to lung volume ratio, and volume of either the lung or the airway tree. Multivariate analyses showed that lower AWV% was associated with lower FEV₁ and higher RV/TLC, independent of LAV%, WA%, and TAC.

Conclusions

A disproportionally small airway tree with a relatively large lung could lead to airflow obstruction and gas trapping in COPD. AWV% is an easily measured CT biomarker that may elucidate the clinical impacts of the airway-lung interaction in COPD.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1047-5) contains supplementary material, which is available to authorized users.

A Patient with GOLD Stage 3 COPD « cured » by One-Way Endobronchial Valves

Lung hyperinflation is a main determinant of dyspnoea in patients with chronic obstructive pulmonary disease (COPD). Surgical or bronchoscopic lung volume reduction are the most efficient therapeutic approaches for reducing hyperinflation in selected patients with emphysema. We here report the case of a 69-year old woman with COPD (GOLD stage 3-D) referred for lung volume reduction. She complained of persistent disabling dyspnoea despite appropriate therapy. Chest imaging showed marked emphysema heterogeneity as well as severe hyperinflation of the right lower lobe. She was deemed to be a good candidate for bronchoscopic treatment with one-way endobronchial valves. In the absence of interlobar collateral ventilation, 2 endobronchial valves were placed in the right lower lobe under general anaesthesia. The improvement observed 1 and 3 months after the procedure was such that the patient no longer met the pulmonary function criteria for COPD. The benefit persisted after 3 years.

Emphysema and lung volume reduction: the role of radiology

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death worldwide. One of the main findings is pulmonary emphysema in association with chronic bronchitis. Clinical signs, pulmonary function tests and imaging are the current used methods to diagnose and stage emphysema. Lung volume reduction (LVR) and endoscopic lung volume reduction (ELVR) are the current therapeutic options beside lung transplantation in cases of severe emphysema. Nowadays imaging is one of the key factors for the success of these therapies. Especially quantitative computed tomography (CT) with its increasing possibilities has become a viable tool, providing detailed information about distribution and heterogeneity of emphysema. Other imaging techniques like dual-energy CT (DECT) and functional magnetic resonance (MR) have shown to add functional information. These structural and functional information support thoracic surgeons and interventional pulmonologists in selecting patients and optimizing LVR procedures but also enables the development of new endobronchial therapies. Imaging will further improve the individual outcome by supporting the choice of optimal therapy.

Size-capacity mismatch in the lung: a novel predictor for complications after lung cancer surgery

BACKGROUND

The aim of the present study was to make a combined pulmonary functional and anatomical assessment using spirometry and computed tomography (CT) to clarify the best predictor for cardiopulmonary complications after thoracoscopic major lung resection for cancer.

METHODS

We retrospectively reviewed our prospective database of 304 patients undergoing thoracoscopic major lung resection for cancer. The total lung volume (TLV) was measured preoperatively using deep-inspiratory CT by summing the voxels representing -600 to -1024 Hounsfield units. Forced vital capacity (FVC) was measured by spirometry. FVC/TLV was used to diagnose a lung size-function mismatch. We compared among FVC/TLV, conventional spirometric parameters, and the risk of postoperative cardiopulmonary complications.

RESULTS

Postoperative cardiopulmonary complications developed in 25 of 304 patients (8.2%). There were no cases of operative mortality. A stepwise logistic regression analysis revealed that a history of smoking and low FVC/TLV were independent risk factors for postoperative cardiopulmonary complications in various preoperative measurements. According to a receiver-operating characteristic analysis, FVC/TLV was the only variable that was statistically useful for predicting complications (area under the receiver-operating characteristic curve > 0.7).

CONCLUSIONS

Lung size-function mismatch was identified as the best predictor for cardiopulmonary complications after major lung resection for cancer among various spirometry- and CT-derived parameters. The usefulness of this parameter in screening for patients who are at risk of complications should be validated by a multicenter, large-scale study because it can be obtained through routine preoperative work.

Matrix Metalloproteinase-Targeted Imaging of Lung Inflammation and Remodeling

Imaging techniques for detection of molecular and cellular processes that precede or accompany lung diseases are needed. Matrix metalloproteinases (MMPs) play key roles in the development of pulmonary pathology. The objective of this study was to investigate the feasibility of in vivo MMP-targeted molecular imaging for detection of lung inflammation and remodeling.

METHODS

Lung-specific IL-13 transgenic (Club cell 10-kDa protein [CC10]-IL-13 Tg) mice and wild-type littermates were used in this study. Lung structure, gene expression, and MMP activity were assessed by histology, real-time reverse transcription polymerase chain reaction, Western blotting, and zymography. MMP activation was imaged by in vivo small-animal SPECT/CT followed by ex vivo planar imaging. Signal specificity was addressed using a control tracer. The correlation between in vivo MMP signal and gene expression was addressed.

RESULTS

CC10-IL-13 Tg mice developed considerable pulmonary tissue remodeling and inflammation. CD68, MMP-12, and MMP-13 were significantly higher in CC10-IL-13 Tg lungs. On in vivo small-animal SPECT/CT and ex vivo planar images, the MMP signal was significantly higher in the lungs of CC10-IL-13 Tg mice than wild-type animals. Furthermore, a nonbinding analog tracer showed significantly lower accumulation in CC10-IL-13 Tg lungs relative to the specific tracer. There was a significant correlation between small-animal SPECT/CT-derived MMP signal and CD68 expression in the lungs (r = 0.70, P < 0.01).

CONCLUSION

Small-animal SPECT/CT-based MMP-targeted imaging of the lungs is feasible and reflects pulmonary inflammation. If validated in humans, molecular imaging of inflammation and remodeling can potentially help early diagnosis and monitoring of the effects of therapeutic interventions in pulmonary diseases.

Assessment of volume reduction effect after lung lobectomy for cancer

BACKGROUND

Lung lobectomy results in an unexpected improvement of the remaining lung function in some patients with moderate-to-severe emphysema. Because the lung function is the main limiting factor for therapeutic decision making in patients with lung cancer, it may be advantageous to identify patients who may benefit from the volume reduction effect, particularly those with a poor functional reserve.

METHODS

We measured the regional distribution of the emphysematous lung and normal lung using quantitative computed tomography in 84 patients undergoing lung lobectomy for cancer between January 2010 and December 2012. The volume reduction effect was diagnosed using a combination of radiologic and spirometric parameters.

RESULTS

Eight patients (10%) were favorably affected by the volume reduction effect. The forced expiratory volume in one second increased postoperatively in these eight patients, whereas the forced vital capacity was unchanged, thus resulting in an improvement of the airflow obstruction postoperatively. This improvement was not due to a compensatory expansion of the remaining lung but was associated with a relative decrease in the forced end-expiratory lung volume. According to a multivariate analysis, airflow obstruction and the forced end-expiratory lung volume were independent predictors of the volume reduction effect.

CONCLUSIONS

A combined assessment using spirometry and quantitative computed tomography helped to characterize the respiratory dynamics underlying the volume reduction effect, thus leading to the identification of novel predictors of a volume reduction effect after lobectomy for cancer. Verification of our results by a large-scale prospective study may help to extend the indications for lobectomy in patients with oncologically resectable lung cancer who have a marginal pulmonary function.

Longitudinal Computed Tomography and Magnetic Resonance Imaging of COPD: Thoracic Imaging Network of Canada (TINCan) Study Objectives

Although the human and societal burden and cost of COPD is staggering, there are few clinical tools that provide earlier diagnoses or a means to regionally monitor disease in a way that might lead to improved therapies and outcomes. In acknowledgement of the current gaps in COPD therapy, the objective of the Thoracic Imaging Network of Canada (TINCan) is to improve COPD patient phenotyping through imaging, to provide methods and imaging-based intermediate endpoints for the development of new treatments, and to evaluate disease progression and patient-based outcomes in COPD patients and those at risk of COPD. Here we summarize and outline the TINCan study protocol and describe our objectives. TINCan is a prospective study that aims to identify and quantify novel COPD phenotypes from thoracic computed tomography (CT) and thoracic hyperpolarized noble gas magnetic resonance imaging (MRI) in 200 ex-smokers, 50 years of age or greater, including asymptomatic ex-smokers with normal pulmonary function and Global initiative for chronic Obstructive Lung Disease (GOLD) Unclassified (U) , and GOLD stages I-IV patients. Baseline and 2-year follow-up measurements will be acquired using spirometry, plethysmography, diffusing capacity of the lung for carbon monoxide (DLCO), St. George's Respiratory Questionnaire (SGRQ), 6-minute walk test (6MWT), thoracic CT and hyperpolarized helium-3 (3He) and xenon 129 (129Xe) MRI. TINCan provides a unique opportunity to quantify and compare novel lung structure-function measurements and investigate their relationship with well-established clinical measurements and outcomes. Such intermediate endpoints of COPD may be used to stratify patients for personalized treatments and to develop new treatments to improve outcomes, a long-standing clinical goal.

Heterogeneity of lung volume reduction surgery outcomes in patients selected by use of evidence-based criteria

BACKGROUND

Despite its benefit, lung volume reduction surgery (LVRS) is underused, partially because of the heterogeneous responses and lack of recent outcomes data.

METHODS

Data from 59 consecutive emphysema patients who underwent LVRS were analyzed. The proportion of patients responding based on 6-minute walk distance (6-MWD), exercise capacity (watts), and forced expiratory volume in 1 second (FEV1) were calculated. Baseline variables were correlated with improvements in 6-MWD, maximal watts, and FEV1.

RESULTS

Eighty-eight percent of patients responded to LVRS, with a higher proportion of FEV1 and 6-MWD responders in our cohort compared with similar patients from the National Emphysema Treatment Trial. Significant associations existed between lower baseline 6-MWD and increased 6-MWD after operation (r = -0.423), more extensive emphysema and increased FEV1 (r = 0.491), and hyperinflation and increased maximal watts (r = 0.438). The probability of survival was 0.93 at 90 days, 0.90 at 1 year, and 0.80 (3 years). The lowest exercise group (<20 watts on baseline testing) had an increased risk for death (RR 13.3, p = 0.001).

CONCLUSIONS

There were durable improvements in FEV1 and exercise capacity in patients meeting the National Emphysema Treatment Trial criteria. Survival was comparable to that in similar patients from the National Emphysema Treatment Trial; response rates were higher in our cohort for FEV1 and 6-MWD. Those with lower 6-MWD, more emphysema, and more hyperinflation at baseline were most likely to respond to LVRS. Those with lowest exercise capacity at baseline may have a higher risk of death after LVRS.

Assessment of lung volume collapsibility in chronic obstructive lung disease patients using CT

OBJECTIVE

To investigate the collapsibility of the lung and individual lobes in patients with COPD during inspiration/expiration and assess the association of whole lung and lobar volume changes with pulmonary function tests (PFTs) and disease severity.

METHODS

PFT measures used were RV/TLC%, FEV1% predicted, FVC, FEV1/FVC%, DLco% predicted and GOLD category. A total of 360 paired inspiratory and expiratory CT examinations acquired in 180 subjects were analysed. Automated computerised algorithms were used to compute individual lobe and total lung volumes. Lung volume collapsibility was assessed quantitatively using the simple difference between CT computed inspiration (I) and expiration (E) volumes (I-E), and a relative measure of volume changes, (I-E)/I.

RESULTS

Mean absolute collapsibility (I-E) decreased in all lung lobes with increasing disease severity defined by GOLD classification. Relative collapsibility (I-E)/I showed a similar trend. Upper lobes had lower volume collapsibility across all GOLD categories and lower lobes collectively had the largest volume collapsibility. Whole lung and left lower lobe collapsibility measures tended to have the highest correlations with PFT measures. Collapsibility of lung lobes and whole lung was also negatively correlated with the degree of air trapping between expiration and inspiration, as measured by mean lung density. All measured associations were statistically significant (P < 0.01).

CONCLUSION

Severity of COPD appears associated with increased collapsibility in the upper lobes, but change (decline) in collapsibility is faster in the lower lobes.

KEY POINTS

• Inspiratory and expiratory computed tomography allows assessment of lung collapsibility • Lobe volume collapsibility is significantly correlated with measures of lung function. • As COPD severity increases, collapsibility of individual lung lobes decreases. • Upper lobes exhibit more severe disease, while lower lobes decline faster.

Recent findings in chronic obstructive pulmonary disease by using quantitative computed tomography

Chronic obstructive pulmonary disease (COPD) is characterized by an incompletely reversible airflow limitation that results from a combination of airway wall remodeling and emphysematous lung destruction. Forced expiratory volume in 1s (FEV(1)) has been considered the gold standard for diagnosis, classification, and follow-up in patients with COPD, but it has certain limitations and it is still necessary to find other noninvasive modalities to complement FEV(1) to evaluate the effect of therapeutic interventions and the pathogenesis of COPD. Quantitative computed tomography (CT) has partly met this demand. The extent of emphysema and airway dimensions measured using quantitative CT are associated with morphological and functional changes and clinical symptoms in patients with COPD. Phenotyping COPD based on quantitative CT has facilitated interventional and genotypic studies. Recent advances in COPD findings with quantitative CT are discussed in this review.

Quantitative computed tomography in COPD: possibilities and limitations

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease that is characterized by chronic airflow limitation. Unraveling of this heterogeneity is challenging but important, because it might enable more accurate diagnosis and treatment. Because spirometry cannot distinguish between the different contributing pathways of airflow limitation, and visual scoring is time-consuming and prone to observer variability, other techniques are sought to start this phenotyping process. Quantitative computed tomography (CT) is a promising technique, because current CT technology is able to quantify emphysema, air trapping, and large airway wall dimensions. This review focuses on CT quantification techniques of COPD disease components and their current status and role in phenotyping COPD.

A randomized study of endobronchial valves for advanced emphysema

BACKGROUND

Endobronchial valves that allow air to escape from a pulmonary lobe but not enter it can induce a reduction in lobar volume that may thereby improve lung function and exercise tolerance in patients with pulmonary hyperinflation related to advanced emphysema.

METHODS

We compared the safety and efficacy of endobronchial-valve therapy in patients with heterogeneous emphysema versus standard medical care. Efficacy end points were percent changes in the forced expiratory volume in 1 second (FEV1) and the 6-minute walk test on intention-to-treat analysis. We assessed safety on the basis of the rate of a composite of six major complications.

RESULTS

Of 321 enrolled patients, 220 were randomly assigned to receive endobronchial valves (EBV group) and 101 to receive standard medical care (control group). At 6 months, there was an increase of 4.3% in the FEV1 in the EBV group (an increase of 1.0 percentage point in the percent of the predicted value), as compared with a decrease of 2.5% in the control group (a decrease of 0.9 percentage point in the percent of the predicted value). Thus, there was a mean between-group difference of 6.8% in the FEV1 (P=0.005). Roughly similar between-group differences were observed for the 6-minute walk test. At 12 months, the rate of the complications composite was 10.3% in the EBV group versus 4.6% in the control group (P=0.17). At 90 days, in the EBV group, as compared with the control group, there were increased rates of exacerbation of chronic obstructive pulmonary disease (COPD) requiring hospitalization (7.9% vs. 1.1%, P=0.03) and hemoptysis (6.1% vs. 0%, P=0.01). The rate of pneumonia in the target lobe in the EBV group was 4.2% at 12 months. Greater radiographic evidence of emphysema heterogeneity and fissure completeness was associated with an enhanced response to treatment.

CONCLUSIONS

Endobronchial-valve treatment for advanced heterogeneous emphysema induced modest improvements in lung function, exercise tolerance, and symptoms at the cost of more frequent exacerbations of COPD, pneumonia, and hemoptysis after implantation. (Funded by Pulmonx; ClinicalTrials.gov number, NCT00129584.)

Diagnostic imaging in COPD

Chronic obstructive pulmonary disease (COPD) is a pathological pulmonary condition characterized by expiratory airflow obstruction due to emphysematous destruction of the lung parenchyma and small airways remodeling. Although spirometry is a very useful diagnostic tool for screening large groups of smokers, it cannot readily differentiate the etiologies of COPD and thus has limited utility in characterizing subjects for clinical and investigational purposes. There has been a longstanding interest in thoracic imaging and its role in the in vivo characterization of smoking-related lung disease. Research in this area has spanned readily available modalities such as chest -ray and computed tomography to more advanced imaging techniques such as optical coherence tomography (OCT) and magnetic resonance imaging (MRI). Although the chest x-ray is almost universally available, it lacks sensitivity in detecting both airway disease and mild emphysema and is not generally amenable to objective analysis. Computed tomography has become the standard modality to objectively visualize lung disease. It can provide useful measures of the presence and extent of emphysema, airway disease, and, more recently, pulmonary vascular disease for clinical correlation. It does, however, face limitations in standardization across brands and generations of scanners, and the ionizing radiation associated with image acquisition is of concern to both patients and health care providers. Newer techniques such as OCT and MRI offer exciting in vivo insights into lung structure and function that were previously available only in necropsy specimens and physiology laboratories. Given the more limited availability of these techniques, they will be viewed here as adjuncts to computed tomographic imaging.

Are airflow obstruction and radiographic evidence of emphysema risk factors for lung cancer? A nested case-control study using quantitative emphysema analysis

OBJECTIVES

Several studies have identified airflow obstruction as a risk factor for lung cancer independent of smoking history, but the risk associated with the presence of radiographic evidence of emphysema has not been extensively studied. We proposed to assess this risk using a quantitative volumetric CT scan analysis.

METHODS

Sixty-four cases of lung cancer were identified from a prospective cohort of 1,520 participants enrolled in a spiral CT scan lung cancer screening trial. Each case was matched to six control subjects for age, sex, and smoking history. Quantitative CT scan analysis of emphysema was performed. Spirometric measures were also conducted. Data were analyzed using conditional logistic regression making use of the 1:6 set groups of 64 cases and 377 matched control subjects.

RESULTS

Decreased FEV(1) and FEV(1)/FVC were significantly associated with a diagnosis of lung cancer with ORs of 1.15 (95% CI, 1.00-1.32; P = .046) and 1.29 (95% CI, 1.02-1.62; P = .031), respectively. The quantity of radiographic evidence of emphysema was not found to be a significant risk for lung cancer with OR of 1.042 (95% CI, 0.816-1.329; P = .743). Additionally, there was no significant association between severe emphysema and lung cancer with OR of 1.57 (95% CI, 0.73-3.37).

CONCLUSIONS

We confirm previous observations that airflow obstruction is an independent risk factor for lung cancer. The absence of a clear relationship between radiographic evidence of emphysema and lung cancer using an automated quantitative volumetric analysis may result from different population characteristics than those of prior studies, radiographic evidence of emphysema quantitation methodology, or absence of any relationship between emphysema and lung cancer risk.

Carbon monoxide diffusing capacity and mortality in pulmonary arterial hypertension

BACKGROUND

Abnormal carbon monoxide diffusing capacity (DLCO) is a marker of pulmonary vascular disease and predicts the presence of pulmonary arterial hypertension (PAH) and poor prognosis in diseases such as systemic sclerosis and idiopathic pulmonary fibrosis. Little is known of its prognostic utility in World Health Organization (WHO) Group I PAH.

METHODS

We performed a cohort study of 408 patients with WHO Group I PAH from 1982 to 2006, with data on demographics, comorbidities, medications, functional class, laboratory tests, exercise testing, and hemodynamics. DLCO was determined upon entry into the study. We divided the cohort into tertiles based on DLCO and compared differences between groups. We used a Cox proportional hazards analysis to determine the association of DLCO with mortality, after adjusting for age, connective tissue disease etiology, functional class, pulmonary function testing variables, serum creatinine, albumin, hemoglobin, lung parenchymal abnormalities on chest computed tomography, oxygen use, and hemodynamic variables.

RESULTS

The lowest tertile of DLCO was independently associated with an increased risk of death (univariate hazard ratio [HR] = 2.7, 95% confidence interval [CI] 1.9 to 3.9, p < 0.0001; multivariate HR = 2.4, 95% CI 1.1 to 5.0, p = 0.025). On receiving operator characteristic (ROC) curve analysis, the c-statistic for the multivariate model without DLCO was 0.75, whereas the c-statistic for the multivariate model with DLCO was 0.78 (p = 0.003 by likelihood ratio test). Importantly, a multivariate model with hemodynamic variables alone (c-statistic = 0.61) was quite inferior to the multivariate model, which included DLCO.

CONCLUSION

DLCO is an independent predictor of death in patients with WHO Group I PAH.

Physiological and computed tomographic predictors of outcome from lung volume reduction surgery

RATIONALE

Previous investigations have identified several potential predictors of outcomes from lung volume reduction surgery (LVRS). A concern regarding these studies has been their small sample size, which may limit generalizability. We therefore sought to examine radiographic and physiologic predictors of surgical outcomes in a large, multicenter clinical investigation, the National Emphysema Treatment Trial.

OBJECTIVES

To identify objective radiographic and physiological indices of lung disease that have prognostic value in subjects with chronic obstructive pulmonary disease being evaluated for LVRS.

METHODS

A subset of the subjects undergoing LVRS in the National Emphysema Treatment Trial underwent preoperative high-resolution computed tomographic (CT) scanning of the chest and measures of static lung recoil at total lung capacity (SRtlc) and inspiratory resistance (Ri). The relationship between CT measures of emphysema, the ratio of upper to lower zone emphysema, CT measures of airway disease, SRtlc, Ri, the ratio of residual volume to total lung capacity (RV/TLC), and both 6-month postoperative changes in FEV(1) and maximal exercise capacity were assessed.

MEASUREMENTS AND MAIN RESULTS

Physiological measures of lung elastic recoil and inspiratory resistance were not correlated with improvement in either the FEV(1) (R = -0.03, P = 0.78 and R = -0.17, P = 0.16, respectively) or maximal exercise capacity (R = -0.02, P = 0.83 and R = 0.08, P = 0.53, respectively). The RV/TLC ratio and CT measures of emphysema and its upper to lower zone ratio were only weakly predictive of postoperative changes in both the FEV(1) (R = 0.11, P = 0.01; R = 0.2, P < 0.0001; and R = 0.23, P < 0.0001, respectively) and maximal exercise capacity (R = 0.17, P = 0.0001; R = 0.15, P = 0.002; and R = 0.15, P = 0.002, respectively). CT assessments of airway disease were not predictive of change in FEV(1) or exercise capacity in this cohort.

CONCLUSIONS

The RV/TLC ratio and CT measures of emphysema and its distribution are weak but statistically significant predictors of outcome after LVRS.

Lung volume reduction surgery in nonheterogeneous emphysema

Patients with a homogeneous type of emphysema have been excluded a priori from LVRS in many centers because of the fear of removing parenchyma, which potentially contributes to gas exchange, and because the observation that heterogeneity of emphysema is a predictor of functional improvement. It is obvious that resection of functionless tissue, such as in heterogeneous emphysema with bullae, can be advised to the patient with a relative low risk. However, as the main positive effect of LVRS is its improvement on respiratory mechanics, it is not surprising that well-selected patients with homogeneous emphysema also benefit from surgery. Their selection has to be done cautiously. It is crucial to exclude patients with a very low functional reserve, such as with diffusing capacity below 20% predicted or with pulmonary hypertension, and with extreme parenchymal loss (vanished lungs) on CT from LVRS. Additionally, cofactors which may potentially interfere with a smooth postoperative course, such as previous recurrent infections, extensive scarring of the lungs, or previous surgery, have to be taken into consideration. When respecting these caveats, LVRS in patients with complete homogeneous emphysema provides a comparable symptomatic and almost the same functional improvement as in patients with heterogeneous emphysema. Although the perioperative mortality is low, patients with homogeneous emphysema have a slightly reduced long-term survival without lung transplantation compared with patients with heterogeneous emphysema. Based on our own experience, we conclude that LVRS can be recommended to selected symptomatic patients with advanced homogenous emphysema associated with severe hyperinflation, if diffusing capacity is not below 20% of predicted values and if the CT scan does not show aspects of vanished lungs.

Radiographic evaluation of the potential lung volume reduction surgery candidate

Delineating the extent and distribution of emphysema is an essential component of the evaluation of candidates for lung volume reduction surgery (LVRS). Imaging also may identify contraindications to LVRS, including bronchiectasis and pleural scarring. The chest X-ray is of limited utility in LVRS evaluation. Chest computed tomography (CT) scanning is an essential component of the evaluation, demonstrating the presence of emphysema and its amount and distribution. Clinical experience has shown that a substantial minority of chest CT scans will also demonstrate pulmonary nodules, some of which represent lung cancers. Published series, including the National Emphysema Treatment Trial, consistently demonstrate that patients with upper lobe predominant or heterogeneous emphysema are most likely to benefit from LVRS. Heterogeneity and distribution can also be assessed by radionuclide ventilation perfusion scanning, but this modality adds little additional information to CT scanning.

New 133Xe gas trapping index for quantifying severe emphysema before partial lung volume reduction

Lung volume reduction (LVR) is an effective therapy for end-stage emphysema. Preliminary and postprocedure imaging is usually limited to CT for anatomic delineation of the location and severity of the most acutely affected lung zones. The purpose of this study was to investigate the potential of using a new quantitative gas trapping index (GTI) derived from a (133)Xe ventilation scan to assess the severity of emphysema.

METHODS

Using the equilibration and washout phases of a (133)Xe ventilation study, a GTI was compared with visual National Emphysema Treatment Trial (NETT) CT scoring, semiautomated CT densitometry, and (99m)Tc perfusion scintigraphy in 28 patients being evaluated for LVR. The GTI was calculated as the percentage of (133)Xe gas retention in a 3-min washout image compared with the peak equilibrium image for 6 lung zones.

RESULTS

The GTI correlated best with the percentage of perfusion (-0.39, P<0.0001) and the CT density scoring with the percentage of severe emphysema (0.36, P<0.0001). There was less correlation with visual NETT CT scores (0.25, P<0.001).

CONCLUSION

This GTI, based on widely available (133)Xe imaging, shows good correlation with other quantitative measures of emphysema that are anatomically based. Because this GTI provides a more functional assessment of gas trapping and airway disease, these results suggest that additional study is warranted to investigate its use as a functional measure of emphysema before and after LVR.

Computerized estimation of the lung volume removed during lung volume reduction surgery

RATIONALE AND OBJECTIVES

This study was designed to develop an automated method for estimating lung volume removed during lung volume reduction surgery (LVRS) using computed tomography (CT).

MATERIALS AND METHODS

The CT examinations of six patients who underwent bilateral LVRS were analyzed in this study. The resected lung tissue (right and left) was weighed during pathologic examination. An automated computer scheme was developed to estimate the lung volume removed using the CT voxel values and lung specimen weight. The computed fraction of lung volume removed was evaluated across a range of simulated surgical planes (ie, other than parallel to the CT image plane) and CT reconstruction kernels, and it was compared with the surgeons' postsurgical estimates.

RESULTS

The computed fraction of the lung volume removed during LVRS was linearly correlated with the resected lung tissue weight (Pearson correlation = 0.697, P = .012). The computed fraction of lung volume removed ranged from 12.9% to 51.7% of the total lung volume. The surgeons' postsurgical estimates of lung volume removed ranged from 30% to 33%. The percent difference between the surgeons' estimates and the computed lung volume removed as a percentage of the surgeons' estimates ranged from -72.3% to 57.0% with mean absolute difference of 29.7% (+/-20.7).

CONCLUSION

The preliminary findings of this study suggest that the proposed quantitative model should provide an objective measure of lung volume removed during LVRS that may be used to investigate the relationship between lung volume removed and outcome.

Short- and long-term outcome of lung volume reduction surgery. The predictive value of the preoperative clinical status and lung scintigraphy

The NETT study assessed the benefits of lung volume reduction surgery (LVRS) versus medical treatment. However, data is available only on the early outcome of LVRS (24 months). We evaluate the factors affecting the outcome at one-year and up to 6 years after LVRS. Thirty-seven patients underwent LVRS. Thirty-five patients, who survived the operation for at least one-year, were followed up to 6 years. Patients' laboratory, clinical and scintigraphic data before surgery were reviewed retrospectively, and follow-up at one-year and at the end of data collection. Successful LVRS with improvement of FEV(1)30% at one-year was observed in 13 of 35 patients. Five of these patients had initial FEV(1) values of <20% of the predicted. The group of patients with improvement was younger as compared to the 22 patients without improvement (P<0.005). The younger age group used less supplemental oxygen and had a PDiff of >23%. Combinations of age under 60 years and PDiff >23% were a favorable factor (P<0.002) for successful LVRS. Thirty-four patients were followed up to 6 years. Fifteen of the 34 patients (44.1%) remained well. Use of supplemental oxygen before surgery, and FEV(1) improvement of 30% at one-year after surgery were good prognostic factors. We concluded that the long-term success of LVRS is affected by non-dependence on oxygen supplementation before surgery, and the one-year post-surgical improvement of FEV(1) (30%). Based on our findings, the subgroup of patients below 60 years old with severe disease (FEV(1)<20%) and heterogeneous upper lobe emphysema (Pdiff>23%) has improved outcome.

Lung volume reduction surgery for emphysema: What the radiologist needs to know

Imaging plays a pivotal role in the selection of patients for the surgical treatment of emphysema. In this article, the imaging features of emphysema are reviewed along with the surgical options for treatment. Particular emphasis is given to lung volume reduction surgery as this technique has gained wide acceptance within the thoracic surgical community in recent years. Radiologists need to have an understanding of which patients may be potentially suitable for this technique.

Quantitative computed tomography of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is described as airflow limitation that is not fully reversible. Quantitative assessment of structural changes within the lung that are responsible for this airflow limitation has relied on the examination of tissue obtained from surgical or postmortem specimens. However, in the past two decades, researchers have developed novel and robust tools to measure the structure of the lung parenchyma and airway wall by using computed tomographic (CT) scans, which do not require the removal of lung tissue. These techniques are extremely important because they allow longitudinal studies of the pathogenesis of COPD and the assessment of therapeutic interventions. Another application of this approach is that it potentially allows phenotyping of individuals who predominately have emphysema or small-airway disease, which may be important for the evaluation of pathogenesis and prescription of treatment options. This review describes some of these CT techniques for quantitative assessment of lung structure.

Use of CT Morphometry To Detect Changes in Lung Weight and Gas Volume

STUDY OBJECTIVES

CT estimates of lung density have been used to estimate the extent and severity of emphysema. The present study was designed to test the hypothesis that quantitative CT can track the changes that occur in diffuse lung disease.

DESIGN

The study was based on five patients with pulmonary alveolar proteinosis (PAP) who underwent lung lavage. Pulmonary function was measured before and after each individual lung lavage, and the CT scans before and after lavage were used to compare total lung volume, airspace volume, lung weight, and regional lung inflation. The dry weight of proteinaceous material lavaged from the lung was measured and compared to the change in CT lung weight.

RESULTS

All the patients showed improvements in dyspnea, percentage of predicted diffusion capacity of the lung for carbon monoxide, and FVC. There was no change in CT-measured total lung volume or airspace volume, but there was a reduction in lung weight following lavage (p = 0.001), which correlated with the dry weight of the lavage effluent (R(2) = 0.73). Therefore, there was a shift in the regional lung inflation toward a more inflated lung with a corresponding increase in the mean lung inflation (p = 0.001).

CONCLUSION

These data show that quantitative CT can objectively track the changes in lung weight and airspace inflation produced by a standard intervention in PAP, and we postulate that it can provide similar information about the progression of other diffuse lung diseases.

Lung volume reduction surgery as a bridge to lung transplantation

Lung volume reduction surgery (LVRS) improves lung function, exercise capacity, and quality of life in patients with advanced emphysema. In some patients with emphysema who are candidates for lung transplantation, LVRS is an alternative treatment option to lung transplantation, or may be used as a bridge to lung transplantation. Generally accepted criteria for LVRS include severe non-reversible airflow obstruction due to emphysema associated with significant evidence of lung hyperinflation and air trapping. Both high resolution computed tomography (CT) scan of the chest and quantitative ventilation/perfusion scan are used to identify lung regions with severe emphysema which would be used as targets for lung resection. Bilateral LVRS is the preferred surgical approach compared with the unilateral procedure because of better functional outcome. Lung transplantation is the preferred surgical treatment in patients with emphysema with alpha1 antitrypsin deficiency and in patients with very severe disease who have homogeneous emphysema pattern on CT scan of the chest or very low diffusion capacity.

Perfil radiológico do candidato ideal à cirurgia redutora de volume pulmonar no enfisema: uma revisão sistemática

INTRODUÇÃO: A cirurgia redutora de volume pulmonar é uma alternativa terapêutica para o enfisema pulmonar avançado. A avaliação radiológica do tipo e distribuição do enfisema parece ser o principal critério de indicação cirúrgica, além da função pulmonar. OBJETIVO: Determinar o nível de evidência científica referente ao padrão radiológico do candidato ideal à cirurgia redutora de volume pulmonar. MÉTODO: Revisão sistemática da literatura entre janeiro de 1994 e janeiro de 2004, utilizando as bases de dados: MEDLINE, EMbase, LILACS, The Cochrane Library e EBM Reviews. RESULTADOS: Foram identificados 208 artigos e 16 deles preenchiam os critérios do estudo. Destes, dois eram randomizados (um multicêntrico, denominado National Emphysema Treatment Trial, envolvendo 1.218 pacientes; e outro que, embora randomizado, com apenas 30 pacientes). Os 14 remanescentes eram estudos observacionais. O National Emphysema Treatment Trial identificou um subgrupo de pacientes de prognóstico favorável, quando submetidos à cirurgia redutora de volume pulmonar, formado por portadores de enfisema pulmonar avançado e heterogêneo, com predomínio nos lobos superiores, na presença de hiperdistensão pulmonar difusa e baixa capacidade para exercícios físicos. O padrão dos resultados dos demais estudos foi consistente na análise individual, apesar de sua heterogeneidade. Benefício cirúrgico, taxas de mortalidade e qualidade de vida também foram mensurados nos estudos observacionais. CONCLUSÃO: O perfil radiológico caracterizado pelo tipo de enfisema, sua heterogeneidade, distribuição e presença de hiperdistensão difusa, ao lado do nível de gravidade, representa o principal fator preditor de bom resultado cirúrgico. Esta recomendação tem o nível de evidência B, pela escassez de trabalhos na literatura.

Model-based versus clinical prediction of the spirometric response to lung volume reduction surgery

BACKGROUND

Lung volume reduction surgery (LVRS) improves symptoms and lung function in selected patients with severe emphysema.

OBJECTIVES

We investigated whether models based on physiologic and radiologic predictors discriminated patients with a favorable from those with a poor spirometric response to LVRS.

METHODS

Data of a derivation cohort of 70 patients who had previously undergone LVRS served to develop two types of prediction models, lookup functions and logistic regression equations. Presence or absence of improvement in forced expiratory volume in 1 s (FEV1) > or =300 ml and forced vital capacity (FVC) > or =500 ml represented dichotomous outcomes. The residual volume/total lung capacity ratio, CT-radiological emphysema heterogeneity scores and diffusing capacity, a marker of emphysema severity, were the predictors. Models were used to predict spirometric outcomes for a validation cohort of 60 emphysema patients referred for LVRS. Furthermore, the surgeon preoperatively estimated outcomes based on all available clinical data but blinded to model predictions. Spirometric changes within 6 months following surgery were compared to predictions.

RESULTS

Median FEV1 in the validation cohort increased from 0.69 to 1.00 liters (+41%), and FVC from 2.07 to 2.78 liters (+29%; p < 0.05 for changes). Lookup functions and logistic regression equations identified patients experiencing major increases in FEV1 > or =300 ml and FVC > or =500 ml with an accuracy quantified by areas under the receiver-operating characteristic curves of 0.72 to 0.76 (all areas >0.5, p < 0.05). Predictions by the surgeon had an accuracy of 0.71 to 0.78 (p = NS vs. models).

CONCLUSIONS

The accuracy of models based on three predictors was fair and similar to assessment by an experienced surgeon based on all available clinical information. Prediction models may contribute to the consistent assessment of LVRS candidates.

Peripheral solitary pulmonary nodule: CT findings in patients with pulmonary emphysema

PURPOSE

To analyze retrospectively the computed tomographic (CT) features of peripheral noncalcified solitary pulmonary nodules in patients with and those without emphysema.

MATERIALS AND METHODS

The authors' institutional review board required neither its approval nor patient informed consent for this retrospective study. The authors retrospectively reviewed 2-mm-thick CT images of 41 nodules (21 malignant, 20 benign) in 41 patients with emphysema (age range, 58-88 years; mean, 71.9 years) and 40 nodules (20 malignant, 20 benign) in 40 patients without emphysema (age range, 50-85 years; mean, 69.2 years). Two radiologists who were unaware of the diagnosis independently evaluated the shape and margin of the nodule, recorded the presence of ground-glass opacities and air bronchograms, and classified nodules into two diagnostic categories: malignant and benign. Final decisions were reached by consensus. For quantitative assessment of the nodules, the fractal dimensions of the nodule interfaces and circularity of the nodule shape were calculated with an image-processing program, and the percentage of the nodule surrounded by emphysema was obtained. Statistical comparisons were made with a chi(2) or Fisher exact test and the Mann-Whitney U test.

RESULTS

In patients with emphysema, there were no significant differences in fractal dimension, circularity, or frequency of lobulation or spiculation between malignant and benign nodules. Of the 41 nodules in patients with emphysema, 26 (63%) were correctly diagnosed. Thirteen benign nodules (65%) were diagnosed as malignant in patients with emphysema. Of the 40 nodules in nonemphysematous lungs, 37 (93%) were correctly diagnosed. The mean percentage of emphysema around the nodule was greater for misdiagnosed nodules than for correctly diagnosed nodules (P = .003).

CONCLUSION

Malignant and benign nodules associated with emphysema exhibited considerably more overlap in CT features than did nodules in nonemphysematous lungs.

Small airway morphometry and improvement in pulmonary function after lung volume reduction surgery

We examined small airway morphometry from resected lung specimens in 25 patients with severe emphysema undergoing lung volume reduction surgery (LVRS) and correlated their pathologic findings to changes in FEV(1) 6 months after LVRS. Patients were classified into two groups: responders had a more than 12% and a more than 200-ml change in FEV(1) at 6 months, and nonresponders had 12% or less and/or 200 ml or less change in FEV(1). Epithelial height (EH) and perimeters and areas of peribronchial smooth muscle, epithelium, and subepithelial space were measured quantitatively. The degrees of interstitial fibrosis, vascular sclerosis, goblet cell hyperplasia, squamous metaplasia, chronic inflammation, peribronchial fibrosis, and bullous disease were assessed semiquantitatively. Despite similar baseline characteristics, nonresponders had a greater EH (0.045 vs. 0.035 mm, p = 0.025), greater EH adjusted for basement membrane perimeter (0.040 vs. 0.011, p = 0.016), greater epithelial area adjusted for basement membrane area (0.561 vs. 0.499, p = 0.040), and less bullous disease (1.7 vs. 2.6, p = 0.011) compared with responders. We found a linear relationship between percentage change in FEV(1) and bullous disease and inverse relationships between percentage change in FEV(1) and interstitial fibrosis, goblet cell hyperplasia, peribronchial fibrosis, and vascular sclerosis. We conclude that small airway morphometry and lung histopathology in patients with severe emphysema have an important influence on changes in FEV(1) 6 months after LVRS.

Early Emphysema in Patients with Anorexia Nervosa

Postmortem studies of patients who died in the Warsaw Ghetto during World War II suggested that death from starvation was associated with pulmonary emphysema. This study re-examines this hypothesis in patients who are chronically malnourished because of anorexia nervosa. Age, smoking history, body mass index, and pulmonary function were measured in 21 subjects with anorexia nervosa and 16 control subjects. Computed tomography (CT) scans were obtained from three regions of the lung (at the level of the aortic arch, the carina, and the posterior position of the eighth rib) using a multislice scanner. The CT measurements of lung density, emphysema, and surface area-to-volume ratio were obtained using the X-ray attenuation values. CT measurements of emphysema were greater in the group that was anorexic than in historical control subjects (p < 0.001). Furthermore, there were significant correlations between the body mass index and the CT measures of emphysema for all the patients and between diffusing capacity and the CT measurements in the patients who were anorexic. A multiple linear regression analysis showed the diffusing capacity was predicted best by the percentage of lung voxels within the large emphysematous changes category. These data demonstrate that emphysema-like changes are present in the lungs of patients who are chronically malnourished.

Size and Morphology of the Trachea Before and After Lung Volume Reduction Surgery

OBJECTIVE

The purpose of this investigation was to determine the effect of lung volume reduction surgery on measured tracheal features.

MATERIALS AND METHODS

Twenty-four male and 19 female patients with emphysema underwent lung volume reduction surgery, pulmonary function testing, and repeated CT. The tracheal air column was segmented from axial images. The sagittal and coronal dimensions of the intrathoracic trachea were determined. Tracheal morphology was quantified using the tracheal (coronal and sagittal dimensions) and circularity indexes. The results were compared with pulmonary function test results.

RESULTS

Morphologic appearance of the intrathoracic trachea was consistent before and 3 months after surgery. The group means of the tracheal length, mean area, and volume were 78.60 mm (+/- 16.88 mm), 283.84 mm(2) (+/- 61.47 mm(2)), and 22.59 cm(3) (+/- 7.69 cm(3)), respectively, before surgery and 67.53 mm (+/- 15.78 mm), 309.12 mm(2) (+/- 79.83 mm(2)), and 20.99 cm(3) (+/- 7.27 cm(3)), respectively, after surgery (p < 0.05). Mean tracheal indexes were 0.85 (+/- 0.11) before surgery and 0.82 (+/- 0.04) after surgery (p < 0.01). Mean circularity indexes were 0.91 (+/- 0.03) before surgery and 0.90 (+/- 0.04) after surgery (p < 0.05). The size of the trachea was significantly correlated with lung volume before and after surgery (p < 0.05). The changes in tracheal features and changes in pulmonary function were not correlated (p > 0.05), except for tracheal area (p < 0.05).

CONCLUSION

Our data suggest that tracheal dimensions reflect the severity of emphysema as reflected by increased lung volumes. Tracheal features were poor predictors of changes in postsurgical pulmonary function parameters evaluated in this preliminary study.

Early results of endoscopic lung volume reduction for emphysema

BACKGROUND

We determined the feasibility, safety, and short-term efficacy of bronchoscopic placement of a one-way endobronchial valve in selected bronchopulmonary segments as an alternative to surgical lung volume reduction.

METHODS

A total of 21 patients with incapacitating emphysema who underwent this procedure were studied. All patients had placement of the endobronchial valves into the most emphysematous lung segments. We recorded any major complications or deaths attributed to the procedure and analyzed (1) improvements in the spirometric and functional parameters and quality of life and (2) the radiologic changes compared with the baseline data at 30 and 90 days.

RESULTS

A total of 20 patients had complete follow-up data. There was no mortality in the group studied. The forced expiratory volume at 1 second, forced expiratory volume at 1 second (percentage of predicted), forced vital capacity, and forced vital capacity (percentage of predicted) all improved significantly at 90 days (0.73 +/- 0.26 L vs 0.92 +/- 0.34 L [P =.009]; 33.3% +/- 11.9% vs 42.2% +/- 15.0% [P =.006]; 1.94 +/- 0.62 L vs 2.25 +/- 0.61 L [P =.015]; and 63.3% +/- 17.6% vs 73.9% +/- 17.1% [P =.012], respectively). The 6-minute walking distance improved at 30 and 90 days (251.6 +/- 100.2 m vs 306.3 +/- 112.3 m and 322.3 +/- 129.7 m; P =.012 and P =.003). The results of the 36-Item Short-Form Health Survey and the St George Respiratory Questionnaire showed significant improvements at 90 days. The Medical Research Council dyspnea grade also improved significantly at 30 and at 90 days (P =.006 and P =.003, respectively).

CONCLUSIONS

Endobronchial valve placement is a safe procedure, with significant short-term improvements in functional status, quality of life, and relief of dyspnea in selected patients with emphysema. A larger study with long-term follow-up is therefore warranted.

Automated lung segmentation in X-ray computed tomography: development and evaluation of a heuristic threshold-based scheme

RATIONALE AND OBJECTIVES

To develop and evaluate a reliable, fully-automated lung segmentation scheme for application in X-ray computed tomography.

MATERIALS AND METHODS

The automated scheme was heuristically developed using a slice-based, pixel-value threshold and two sets of classification rules. Features used in the rules include size, circularity, and location. The segmentation scheme operates slice-by-slice and performs three key operations: (1) image preprocessing to remove background pixels, (2) computation and application of a pixel-value threshold to identify lung tissue, and (3) refinement of the initial segmented regions to prune incorrectly detected airways and separate fused right and left lungs.

RESULTS

The performance of the automated segmentation scheme was evaluated using 101 computed tomography cases (91 thick slice, 10 thin slice scans). The 91 thick cases were pre- and post-surgery from 50 patients and were not independent. The automated scheme successfully segmented 94.0% of the 2,969 thick slice images and 97.6% of the 1,161 thin slice images. The mean difference of the total lung volumes calculated by the automated scheme and functional residual capacity plus 60% inspiratory capacity was -24.7 +/- 508.1 mL. The mean differences of the total lung volumes calculated by the automated scheme and an established, commonly used semi-automated scheme were 95.2 +/- 52.5 mL and -27.7 +/- 66.9 mL for the thick and thin slice cases, respectively.

CONCLUSION

This simple, fully-automated lung segmentation scheme provides an objective tool to facilitate lung segmentation from computed tomography scans.

Lung-volume reduction surgery for severe emphysema

PURPOSE OF REVIEW

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States, as well as a major cause of disability. In its end stages, its inexorable progression results in profound suffering for those afflicted. Medical therapy has proven largely ineffective in improving dyspnea and functional status, and does not alter pulmonary function. Over the past decade, lung-volume reduction surgery (LVRS) has been proposed as a palliative treatment for certain subgroups of COPD patients with emphysema, but initial enthusiasm over its application had been confounded by uncertainty about the potential cost and morbidities associated with LVRS, as well as durability of its beneficial effects. Longer-term follow-up data of initial uncontrolled trials along with several landmark controlled trials have recently been published, offering insight as to the "proper" place of LVRS in the treatment of these unfortunate patients. This review will summarize and offer perspective on these recent findings, as well as offer thoughts on recent refinements in preoperative imaging assessment, and pioneering efforts in less invasive bronchoscopic lung-volume reduction that should further aid the clinician in defining who should benefit from this treatment approach.

RECENT FINDINGS

Lung-volume reduction surgery can result in demonstrable benefit in selected subgroups of COPD patients with upper-lobe disease and poor exercise capacity before surgery with improvements in six-minute walk distances, forced expiratory volume in the first second (FEV1), dyspnea scores and quality-of-life scores, and decreases in residual volume (RV) as well as the need for supplemental oxygen. Patients with FEV1 less than 20% of predicted and either homogeneous emphysema or diffusing capacities (DLCO) less than 20% of predicted do not benefit from LVRS and have unacceptable peri-operative mortalities. Costs to society are high, with a cost of $98,000 per quality-adjusted-life year gained over a 2-year period if only those with upper-lobe disease are offered the procedure.

SUMMARY

Lung-volume reduction surgery can improve both objective and subjective measures of lung performance in properly selected COPD patients. Durable effects of up to 5 years have now been demonstrated. As costs (both fiscal and emotional) of such an approach are high, refinement in patient selection remains a current goal in the surgical approach to COPD.

Patient selection for lung volume reduction surgery

LVRS represents a valid surgical option for a limited number of patients who have symptomatic emphysema. The results of recent controlled studies have provided a realistic view of LVRS outcomes and yielded a validated algorithm for selection of optimal candidates for surgery. Furthermore, the NETT has provided simultaneously collected cost data that have provided a unique view of the costs and benefits of LVRS in patients who have advanced emphysema. Additional data collection will better define the long-term benefits of such surgical intervention in patients who have COPD.

Selection of patients for lung volume reduction surgery using a power law analysis of the computed tomographic scan

BACKGROUND

A study was undertaken to test the hypothesis that patients respond better to lung volume reduction surgery (LVRS) if their emphysema is confluent and predominantly located in the upper lobes.

METHODS

A density mask analysis was used to identify voxels inflated beyond 10.2 ml gas/g tissue (-910 HU) on preoperative and postoperative CT scans from patients receiving LVRS. These hyperinflated regions were considered to represent emphysematous lesions. A power law analysis was used to determine the relationship between the number (K) and size (A) of the emphysematous lesions in the whole lung and two anatomical regions using the power law equation Y=KA(-D).

RESULTS

The analysis showed a positive correlation between the change in the power law exponent (D) and the change in exercise (Watts) after surgery (r=0.47, p=0.03). There was also a negative correlation between the power law exponent D in the upper region of the lung preoperatively and the change in exercise following surgery (r=-0.60, p<0.05).

CONCLUSIONS

These results confirm that patients with large upper lobe lesions respond better to LVRS than patients with small uniformly distributed disease. Power law analysis of lung CT scans provides a quantitative method for determining the extent and location of emphysema within the lungs of patients with COPD.

Radiologic assessment of emphysema for lung volume reduction surgery

Radiologic imaging is vital to determining whether lung volume reduction surgery (LVRS) is a potential therapeutic option for patients with severe chronic obstructive pulmonary disease. The importance of imaging in patient selection for LVRS has been emphasized by numerous studies relating preoperative imaging features to postoperative outcomes. This article reviews the radiologic features assessed in the LVRS evaluation, summarizes the relationships between preoperative radiologic features and postoperative outcomes, and addresses the limitations of imaging in guiding patient selection.