Relationship between quantitative CT metrics and pulmonary function in combined pulmonary fibrosis and emphysema

Quantitative Imaging Methods in Combined Pulmonary Fibrosis and Emphysema

TOPIC IMPORTANCE

Combined pulmonary fibrosis and emphysema (CPFE) is an underdiagnosed syndrome in which individuals have variable degrees of pulmonary fibrosis and emphysema. Patients with CPFE have high morbidity, including poor exercise tolerance and increased development of comorbidities. CPFE mortality also seems to outpace that of lone emphysema and pulmonary fibrosis. A major limitation to rigorous, large-scale studies of CPFE has been the lack of a precise definition for this syndrome. A 2022 American Thoracic Society/European Respiratory Society/Japanese Respiratory Society/Latin American Thoracic Association research statement called attention to fundamental gaps in our understanding of CPFE and highlighted the potential use of quantitative imaging techniques to better define CPFE.

REVIEW FINDINGS

Broadly, CPFE has been defined using visual interpretation of chest CT imaging documenting the presence of both emphysema and fibrosis, with varying distributions. When quantitative approaches were involved, varying thresholds of emphysema and fibrosis on imaging have been used across different studies.

SUMMARY

This review is structured into three primary themes, starting with early imaging studies, then evaluating the use of quantitative methods and imaging-based thresholds, both in large population studies and single-center cohorts to define CPFE and assess patient outcomes. It concludes by discussing current challenges and how to focus our efforts so that quantitative imaging methods can effectively address the most pressing clinical dilemmas in CPFE.

Combined Pulmonary Fibrosis and Emphysema: Comparative Evidence on a Complex Condition

Combined pulmonary fibrosis and emphysema (CPFE) is a clinical syndrome characterized by upper lobe emphysema and lower lobe fibrosis manifested by exercise hypoxemia, normal lung volumes, and severe reduction of diffusion capacity of carbon monoxide. It has varying prevalence worldwide with a male predominance, and with smoking history of more than 40 pack-years being a common risk factor. The unique imaging features of CPFE emphasize its distinct entity, aiding in the timely detection of pulmonary hypertension and lung cancer, both of which are common complications. High-resolution computed tomography (HRCT) is an important diagnostic and prognostic tool, while lung cancer is an independent factor that alters the prognosis in CPFE patients. Treatment options for CPFE are limited, but smoking cessation, usual treatments of pulmonary fibrosis and emphysema, and avoidance of environmental exposures are encouraged.

Associations of the distance-saturation product and low-attenuation area percentage in pulmonary computed tomography with acute exacerbation in patients with chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) has high global health concerns, and previous research proposed various indicators to predict mortality, such as the distance-saturation product (DSP), derived from the 6-min walk test (6MWT), and the low-attenuation area percentage (LAA%) in pulmonary computed tomographic images. However, the feasibility of using these indicators to evaluate the stability of COPD still remains to be investigated. Associations of the DSP and LAA% with other COPD-related clinical parameters are also unknown. This study, thus, aimed to explore these associations.

Methods

This retrospective study enrolled 111 patients with COPD from northern Taiwan. Individuals' data we collected included results of a pulmonary function test (PFT), 6MWT, life quality survey [i.e., the modified Medical Research Council (mMRC) scale and COPD assessment test (CAT)], history of acute exacerbation of COPD (AECOPD), and LAA%. Next, the DSP was derived by the distance walked and the lowest oxygen saturation recorded during the 6MWT. In addition, the DSP and clinical phenotype grouping based on clinically significant outcomes by previous study approaches were employed for further investigation (i.e., DSP of 290 m%, LAA% of 20%, and AECOPD frequency of ≥1). Mean comparisons and linear and logistic regression models were utilized to explore associations among the assessed variables.

Results

The low-DSP group (<290 m%) had significantly higher values for the mMRC, CAT, AECOPD frequency, and LAA% at different lung volume scales (total, right, and left), whereas it had lower values of the PFT and 6MWT parameters compared to the high-DSP group. Significant associations (with high odds ratios) were observed of the mMRC, CAT, AECOPD frequency, and PFT with low- and high-DSP groupings. Next, the risk of having AECOPD was associated with the mMRC, CAT, DSP, and LAA% (for the total, right, and left lungs).

Conclusion

A lower value of the DSP was related to a greater worsening of symptoms, more-frequent exacerbations, poorer pulmonary function, and more-severe emphysema (higher LAA%). These readily determined parameters, including the DSP and LAA%, can serve as indicators for assessing the COPD clinical course and may can serve as a guide to corresponding treatments.

Syndrome of Combined Pulmonary Fibrosis and Emphysema: An Official ATS/ERS/JRS/ALAT Research Statement

Background: The presence of emphysema is relatively common in patients with fibrotic interstitial lung disease. This has been designated combined pulmonary fibrosis and emphysema (CPFE). The lack of consensus over definitions and diagnostic criteria has limited CPFE research. Goals: The objectives of this task force were to review the terminology, definition, characteristics, pathophysiology, and research priorities of CPFE and to explore whether CPFE is a syndrome. Methods: This research statement was developed by a committee including 19 pulmonologists, 5 radiologists, 3 pathologists, 2 methodologists, and 2 patient representatives. The final document was supported by a focused systematic review that identified and summarized all recent publications related to CPFE. Results: This task force identified that patients with CPFE are predominantly male, with a history of smoking, severe dyspnea, relatively preserved airflow rates and lung volumes on spirometry, severely impaired DlCO, exertional hypoxemia, frequent pulmonary hypertension, and a dismal prognosis. The committee proposes to identify CPFE as a syndrome, given the clustering of pulmonary fibrosis and emphysema, shared pathogenetic pathways, unique considerations related to disease progression, increased risk of complications (pulmonary hypertension, lung cancer, and/or mortality), and implications for clinical trial design. There are varying features of interstitial lung disease and emphysema in CPFE. The committee offers a research definition and classification criteria and proposes that studies on CPFE include a comprehensive description of radiologic and, when available, pathological patterns, including some recently described patterns such as smoking-related interstitial fibrosis. Conclusions: This statement delineates the syndrome of CPFE and highlights research priorities.

Carbon Monoxide Diffusing Capacity (DLCO) Correlates with CT Morphology after Chemo-Radio-Immunotherapy for Non-Small Cell Lung Cancer Stage III

Introduction: Curatively intended chemo-radio-immunotherapy for non-small cell lung cancer (NSCLC) stage III may lead to post-therapeutic pulmonary function (PF) impairment. We hypothesized that the decrease in global PF corresponds to the increase in tissue density in follow-up CTs. Hence, the study aim was to correlate the dynamics in radiographic alterations to carbon monoxide diffusing capacity (DLCO) and FEV1, which may contribute to a better understanding of radiation-induced lung disease. Methods: Eighty-five patients with NSCLC III were included. All of them received two cycles of platinum-based induction chemotherapy followed by high dose radiation. Thereafter, durvalumab was administered for one year in 63/85 patients (74%). Pulmonary function tests (PFTs) were performed three months and six months after completion of radiotherapy (RT) and compared to baseline. At the same time points, patients underwent diagnostic CT (dCT). These dCTs were matched to the planning CT (pCT) using RayStation® Model Based Segmentation and deformable image registration. Differential volumes defined by specific isodoses were generated to correlate them with the PFTs. Results: In general, significant correlations between PFTs and differential volumes were found in the mid-dose range, especially for the volume of the lungs receiving between 65% and 45% of the dose prescribed (V65−45%) and DLCO (p<0.01). This volume range predicted DLCO after RT (p-value 0.03) as well. In multivariate analysis, DLCO (p-value 0.040) and FEV1 (p-value 0.014) predicted pneumonitis. Conclusions: The current analysis revealed a strong relation between the dynamics of DLCO and CT morphology changes in the mid-dose range, which convincingly indicates the importance of routinely used PFTs in the context of a curative treatment approach.

Chronic Obstructive Pulmonary Disease Combined with Interstitial Lung Disease

Although chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD) have distinct clinical features, both diseases may coexist in a patient because they share similar risk factors such as smoking, male sex, and old age. Patients with both emphysema in upper lung fields and diffuse ILD are diagnosed with combined pulmonary fibrosis and emphysema (CPFE), which causes substantial clinical deterioration. Patients with CPFE have higher mortality compared with patients who have COPD alone, but results have been inconclusive compared with patients who have idiopathic pulmonary fibrosis (IPF). Poor prognostic factors for CPFE include exacerbation, lung cancer, and pulmonary hypertension. The presence of interstitial lung abnormalities, which may be an early or mild form of ILD, is notable among patients with COPD, and is associated with poor prognosis. Various theories have been proposed regarding the pathophysiology of CPFE. Biomarker analyses have implied that this pathophysiology may be more closely associated with IPF development, rather than COPD or emphysema. Patients with CPFE should be advised to quit smoking and undergo routine lung function tests, and pulmonary rehabilitation may be helpful. Various pharmacologic agents and surgical approaches may be beneficial in patients with CPFE, but further studies are needed.

Quantifying normal lung in pulmonary fibrosis: CT analysis and correlation with %DLCO

BACKGROUND

Chest CT scans are routinely obtained to monitor disease progression in pulmonary fibrosis. However, radiologists do not employ a standardized system for quantitative description of the severity of the disease. Development and validation of a grading system offers potential for enhancing the information that radiologists provide clinicians.

STUDY DESIGN AND METHODS

Our retrospective review analyzed 100 sequential patients with usual interstitial pneumonitis (UIP) on HRCT scans from 2018 and 2019. A radiologic scoring system evaluated the percent of normal lung on the basis of a 0-5 point scale per lobe (findings for the right middle lobe were included in the right upper lobe score), yielding an overall additive numerical score on a scale of 20 (completely normal lung) to 0 (no normal lung). Two radiologists quantified the percentage of normal lung by consensus agreement. Percent DLCO as well as demographic data were obtained from the medical record. Statistical analysis was performed using Spearman correlation to assess correlation between grade and percent DLCO.

RESULTS

96 patients met the inclusion criteria; average age was 71, 68% were male. Score on CT scan ranged from 18 to 4; average 10.9, SD 3.58. The single-breath diffusing capacity (percent DLCO) ranged from 88% to 17%; mean 44.5%, SD 14.3%. Spearman's correlation for CT score and percent DLCO was 0.622, P < 0.001.

CONCLUSION

This scoring system quantifying the amount of normal lung on chest CT of patients with UIP correlated significantly with percent DLCO (P < 0.001) and appears to offer a promising quantitative measure to assess severity of disease.

Objective quantitative multidetector computed tomography assessments in patients with combined pulmonary fibrosis with emphysema: Relationship with pulmonary function and clinical events

BACKGROUND

Combined pulmonary fibrosis with emphysema (CPFE) is a clinically meaningful syndrome characterized by coexisting upper-lobe emphysema and lower-lobe interstitial fibrosis. However, ambiguous diagnostic criteria and, particularly, the absence of objective methods to quantify emphysematous/fibrotic lesions in patients with CPFE confound the interpretation of the pathophysiology of this syndrome. We analyzed the relationship between objectively quantified computed tomography (CT) measurements and the results of pulmonary function testing (PFT) and clinical events in CPFE patients.

MATERIALS AND METHODS

We enrolled 46 CPFE patients who underwent CT and PFT. The extent of emphysematous lesions was obtained by calculating the percent of low attenuation area (%LAA). The extent of fibrotic lesions was calculated as the percent of high attenuation area (%HAA). %LAA and %HAA values were combined to yield the percent of abnormal area (%AA). We assessed the relationships between CT parameters and other clinical indices, including PFT results. Multivariate analysis was performed to examine the association between the CT parameters and clinical events.

RESULTS

A greater negative correlation with percent predicted diffusing capacity of the lung for carbon monoxide (DLCO %predicted) existed for %AA (r = -0.73, p < 0.001) than for %LAA or %HAA alone. The %HAA value was inversely correlated with percent predicted forced vital capacity (r = -0.48, p < 0.001), percent predicted total lung capacity (r = -0.48, p < 0.01), and DLCO %predicted (r = -0.47, p < 0.01). Multivariate logistic regression analysis found that %AA showed the strongest association with hospitalization events (odds ratio = 1.20, 95% confidence interval = 1.01-1.54, p = 0.029).

CONCLUSION

Quantitative CT measurements reflected deterioration in pulmonary function and were associated with hospitalization in patients with CPFE. This approach could serve as a useful method to determine the extent of lung morphology, pathophysiology, and the clinical course of patients with CPFE.

Risk of radiation pneumonitis in patients with emphysema after stereotactic body radiotherapy for non-small cell lung cancer assessed by quantitative CT

Quantitative CT assessment of patients with pulmonary emphysema is used to measure pulmonary function. The present study evaluated whether the quantitative CT value can accurately estimate the risk of radiation pneumonitis (RP) after stereotactic body radiotherapy (SBRT) for non-small cell lung cancer (NSCLC) in patients with and without emphysema. A total of 80 patients with stage I NSCLC receiving SBRT at a dose of 50 or 60 Gy in five fractions at our hospital between November 2003 and October 2015 were included in the analysis. A total of 33 (41%) patients were diagnosed with emphysema on CT examination. Dosimetric parameters, quantitative CT percentage value of low attenuation area (LAA%) in the whole lung, and average whole lung CT density values were used to examine the risk of RP. Among the 80 patients, 26 (33%) and 3 (4%) experienced Grade 1 and Grade 2 RP, respectively, during the median observation period of 18.8 (1.8-106.8) months. The RP rate for patients with a LAA% (<-910 HU) of ≤25% was significantly higher than that of subjects with LAA% (<-910 HU) >25% (P=0.037). The RP rate in subjects with an average HU value of >-790 HU was significantly higher compared with that of patients with ≤-790 HU (P=0.036). Age (hazard ratio [HR]=2.46; P=0.03) and average HU (HR=3.39; P=0.02) were significantly associated with RP, whereas mean lung dose was not identified to be significant in multivariate analysis. The quantitative CT value was associated with RP after SBRT.

Quantitative CT analysis in patients with pulmonary emphysema: is lung function influenced by concomitant unspecific pulmonary fibrosis?

Purpose

Quantitative analysis of CT scans has proven to be a reproducible technique, which might help to understand the pathophysiology of chronic obstructive pulmonary disease (COPD) and combined pulmonary fibrosis and emphysema. The aim of this retrospective study was to find out if the lung function of patients with COPD with Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages III or IV and pulmonary emphysema is measurably influenced by high attenuation areas as a correlate of concomitant unspecific fibrotic changes of lung parenchyma.

Patients and methods

Eighty-eight patients with COPD GOLD stage III or IV underwent CT and pulmonary function tests. Quantitative CT analysis was performed to determine low attenuation volume (LAV) and high attenuation volume (HAV), which are considered to be equivalents of fibrotic (HAV) and emphysematous (LAV) changes of lung parenchyma. Both parameters were determined for the whole lung, as well as peripheral and central lung areas only. Multivariate regression analysis was used to correlate HAV with different parameters of lung function.

Results

Unlike LAV, HAV did not show significant correlation with parameters of lung function. Even in patients with a relatively high HAV of more than 10%, in contrast to HAV (p=0.786) only LAV showed a significantly negative correlation with forced expiratory volume in 1 second (r=-0.309, R2=0.096, p=0.003). A severe decrease of DLCO% was associated with both larger HAV (p=0.045) and larger LAV (p=0.001). Residual volume and FVC were not influenced by LAV or HAV.

Conclusion

In patients with COPD GOLD stage III-IV, emphysematous changes of lung parenchyma seem to have such a strong influence on lung function, which is a possible effect of concomitant unspecific fibrosis is overwhelmed.

Quantitative CT Evaluation of Small Pulmonary Vessels in Patients with Acute Pulmonary Embolism

RATIONALE AND OBJECTIVES

The objective of this study was to investigate the correlation between the computed tomography (CT) cross-sectional area (CSA) of small pulmonary vessels and the CT obstruction index in patients with acute pulmonary embolism (PE) and the correlation between the changes in these measurements after anticoagulant therapy.

MATERIALS AND METHODS

Fifty-two patients with acute PE were selected for this study. We measured the CSA less than 5 mm² on coronal reconstructed images to obtain the percentage of the CSA (%CSA < 5). CT angiographic index was obtained based on the Qanadli method for the evaluation of the degree of pulmonary arterial obstruction. Spearman rank correlation analysis was used to evaluate the relationship between the initial and the follow-up values and changes in the %CSA < 5 and the CT obstruction index.

RESULTS

There was no significant correlation between the %CSA < 5 and CT obstruction index on both initial (ρ = -0.03, P = 0.84) and follow-up (ρ = -0.03, P = 0.82) assessments. In contrast, there was a significant negative correlation between the changes in %CSA < 5 and the CT obstruction index (ρ = -0.59, P < 0.0001).

CONCLUSIONS

Although the absolute %CSA < 5 and CT obstruction index were not significantly correlated, the changes in the values of the two parameters had a significant correlation. Changes in %CSA < 5, which can be obtained easily, can be used as biomarker of therapeutic response in patients with acute PE.

Idiopathic pulmonary fibrosis: pathogenesis and management

Background

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive disease characterized by the aberrant accumulation of fibrotic tissue in the lungs parenchyma, associated with significant morbidity and poor prognosis. This review will present the substantial advances achieved in the understanding of IPF pathogenesis and in the therapeutic options that can be offered to patients, and will address the issues regarding diagnosis and management that are still open.

Main body

Over the last two decades much has been clarified about the pathogenic pathways underlying the development and progression of the lung scarring in IPF. Sustained alveolar epithelial micro-injury and activation has been recognised as the trigger of several biological events of disordered repair occurring in genetically susceptible ageing individuals. Despite multidisciplinary team discussion has demonstrated to increase diagnostic accuracy, patients can still remain unclassified when the current diagnostic criteria are strictly applied, requiring the identification of a Usual Interstitial Pattern either on high-resolution computed tomography scan or lung biopsy.

Outstanding achievements have been made in the management of these patients, as nintedanib and pirfenidone consistently proved to reduce the rate of progression of the fibrotic process. However, many uncertainties still lie in the correct use of these drugs, ranging from the initial choice of the drug, the appropriate timing for treatment and the benefit-risk ratio of a combined treatment regimen. Several novel compounds are being developed in the perspective of a more targeted therapeutic approach; in the meantime, the supportive care of these patients and their carers should be appropriately prioritized, and greater efforts should be made toward the prompt identification and management of relevant comorbidities.

Conclusions

Building on the advances in the understanding of IPF pathobiology, the further investigation of the role of gene variants, epigenetic alterations and other molecular biomarkers reflecting disease activity and behaviour will hopefully enable earlier and more confident diagnosis, improve disease phenotyping and support the development of novel agents for personalized treatment of IPF.

Evaluation of visual and computer-based CT analysis for the identification of functional patterns of obstruction and restriction in hypersensitivity pneumonitis

BACKGROUND AND OBJECTIVE

To determine whether computer-based quantification (CALIPER software) is superior to visual computed tomography (CT) scoring in the identification of CT patterns indicative of restrictive and obstructive functional indices in hypersensitivity pneumonitis (HP).

METHODS

A total of 135 consecutive HP patients had CT parenchymal patterns evaluated quantitatively by both visual scoring and CALIPER. Results were evaluated against: forced vital capacity (FVC), total lung capacity (TLC), diffusing capacity for carbon monoxide (DL_CO ) and a composite physiological index (CPI) to identify which CT scoring method better correlated with functional indices.

RESULTS

CALIPER-derived scores of total interstitial lung disease extent correlated more strongly than visual scores: FVC (CALIPER R = 0.73, visual R = 0.51); DL_CO (CALIPER R = 0.61, visual R = 0.48); and CPI (CALIPER R = 0·70, visual R = 0·55). The CT variable that correlated most strongly with restrictive functional indices was CALIPER pulmonary vessel volume (PVV): FVC R = 0.75, DL_CO R = 0.68 and CPI R = 0.76. Ground-glass opacity quantified by CALIPER alone demonstrated strong associations with restrictive functional indices: CALIPER FVC R = 0.65; DL_CO R = 0.59; CPI R = 0.64; and visual = not significant. Decreased attenuation lung quantified by CALIPER was a better morphological measure of obstructive lung disease than equivalent visual scores as judged by relationships with TLC (CALIPER R = 0.63 and visual R = 0.12). All results were maintained on multivariate analysis.

CONCLUSION

CALIPER improved on visual scoring in HP as judged by restrictive and obstructive functional correlations. Decreased attenuation regions of the lung quantified by CALIPER demonstrated better linkages to obstructive lung physiology than visually quantified CT scores. A novel CALIPER variable, the PVV, demonstrated the strongest linkages with restrictive functional indices and could represent a new automated index of disease severity in HP.

Functional and prognostic effects when emphysema complicates idiopathic pulmonary fibrosis

This study aimed to investigate whether the combination of fibrosis and emphysema has a greater effect than the sum of its parts on functional indices and outcome in idiopathic pulmonary fibrosis (IPF), using visual and computer-based (CALIPER) computed tomography (CT) analysis.Consecutive patients (n=272) with a multidisciplinary IPF diagnosis had the extent of interstitial lung disease (ILD) scored visually and by CALIPER. Visually scored emphysema was subcategorised as isolated or mixed with fibrotic lung. The CT scores were evaluated against functional indices forced vital capacity (FVC), diffusing capacity of the lungs for carbon monoxide (D_LCO), transfer coefficient of the lung for carbon monoxide (K_CO), composite physiologic index (CPI)) and mortality.The presence and extent of emphysema had no impact on survival. Results were maintained following correction for age, gender, smoking status and baseline severity using D_LCO, and combined visual emphysema and ILD extent. Visual emphysema quantitation indicated that relative preservation of lung volumes (FVC) resulted from tractionally dilated airways within fibrotic lung, ventilating areas of admixed emphysema (p<0.0001), with no independent effect on FVC from isolated emphysema. Conversely, only isolated emphysema (p<0.0001) reduced gas transfer (D_LCO).There is no prognostic impact of emphysema in IPF, beyond that explained by the additive extents of both fibrosis and emphysema. With respect to the location of pulmonary fibrosis, emphysema distribution determines the functional effects of emphysema.

Functional image guided radiation therapy planning in volumetric modulated arc therapy for patients with malignant pleural mesothelioma

PURPOSE

To investigate the incorporation of functional lung image-derived low-attenuation area (LAA) based on 4-dimensional computed tomography (4D-CT) in volumetric modulated arc therapy (VMAT) planning for patients with malignant pleural mesothelioma (MPM) after extrapleural pneumonectomy.

METHODS AND MATERIALS

Twelve patients with MPM after extrapleural pneumonectomy were included. The primarily affected side was the right in 6 patients and the left in 6 patients. LAA was generated from 4D-CT data according to CT values with a threshold of less than -860 Hounsfield units (HU). Functional lung image was defined as the area where LAA was excluded from contralateral lung image. Two radiation therapy plans were designed: (1) Plan C, conventional VMAT and (2) Plan F, functional VMAT plan based on the functional lung. Both plans were compared in each patient with respect to the following dosimetric parameters: fV20, V20, fV10, V10, fV5, and V5, the percentages of functional or contralateral lung volumes irradiated with >20 Gy, 10 Gy, or 5 Gy, respectively; functional mean lung dose (fMLD) and mean lung dose (MLD), the mean dose to the functional or contralateral lung, respectively; maximum dose to the cord; mean doses to the liver and heart; and planning target volume homogeneity index.

RESULTS

fV5 and MLD were significantly lower in Plan F (fV5, median 57.5% in Plan C vs 38.5% in Plan F, P < .01; MLD, median 7.0 Gy in Plan C vs 6.4 Gy in Plan F, P = .04). fV10, V5, and fMLD were also significantly lower in Plan F. Compared with Plan C, planning target volume homogeneity index and liver, heart, and cord doses were not significantly elevated in Plan F.

CONCLUSIONS

Significant reductions in fV5, fV10, fMLD, V5, and MLD were achieved with the functional image guided VMAT plan without negative effects on other factors. LAA-based functional image guided radiation therapy planning in VMAT is a feasible method to spare the functional lung in patients with MPM.

Combined pulmonary fibrosis and emphysema: The many aspects of a cohabitation contract

Combined pulmonary fibrosis and emphysema (CPFE) is a clinical entity characterized by the coexistence of upper lobe emphysema and lower lobe fibrosis. Patients with this condition experience severe dyspnea and impaired gas exchange with preserved lung volumes. The diagnosis of the CPFE syndrome is based on HRCT imaging, showing the coexistence of emphysema and pulmonary fibrosis both in varying extent and locations within the lung parenchyma. Individual genetic background seem to predispose to the development of the disease. The risk of the development of pulmonary hypertension in patients with CPFE is high and related to poor prognosis. CPFE patients also present a high risk of lung cancer. Mortality is significant in patients with CPFE and median survival is reported between 2.1 and 8.5 years. Currently, no specific recommendations are available regarding the management of patients with CPFE. In this review we provide information on the existing knowledge on CPFE regarding the pathophysiology, clinical manifestations, imaging, complications, possible therapeutic interventions and prognosis of the disease.

A comparison of visual and quantitative methods to identify interstitial lung abnormalities

Background

Evidence suggests that individuals with interstitial lung abnormalities (ILA) on a chest computed tomogram (CT) may have an increased risk to develop a clinically significant interstitial lung disease (ILD). Although methods used to identify individuals with ILA on chest CT have included both automated quantitative and qualitative visual inspection methods, there has been not direct comparison between these two methods. To investigate this relationship, we created lung density metrics and compared these to visual assessments of ILA.

Methods

To provide a comparison between ILA detection methods based on visual assessment we generated measures of high attenuation areas (HAAs, defined by attenuation values between −600 and −250 Hounsfield Units) in >4500 participants from both the COPDGene and Framingham Heart studies (FHS). Linear and logistic regressions were used for analyses.

Results

Increased measures of HAAs (in ≥10 % of the lung) were significantly associated with ILA defined by visual inspection in both cohorts (P < 0.0001); however, the positive predictive values were not very high (19 % in COPDGene and 13 % in the FHS). In COPDGene, the association between HAAs and ILA defined by visual assessment were modified by the percentage of emphysema and body mass index. Although increased HAAs were associated with reductions in total lung capacity in both cohorts, there was no evidence for an association between measurement of HAAs and MUC5B promoter genotype in the FHS.

Conclusion

Our findings demonstrate that increased measures of lung density may be helpful in determining the severity of lung volume reduction, but alone, are not strongly predictive of ILA defined by visual assessment. Moreover, HAAs were not associated with MUC5B promoter genotype.

Potential Role of CT Metrics in Chronic Obstructive Pulmonary Disease with Pulmonary Hypertension

PURPOSE

Recent imaging studies demonstrated the usefulness of quantitative computed tomographic (CT) analysis assessing pulmonary hypertension (PH) in patients with chronic obstructive lung disease (COPD-PH). The aim of this study was to investigate whether it would be also valuable for predicting and evaluating the effect of pulmonary vasodilators in patients with COPD-PH.

METHODS

We analyzed a correlation between the extent of cystic destruction (LAA%) and total cross-sectional areas of small pulmonary vessels less than 5 mm(2) (%CSA <5) in many CT slices from each of four COPD-PH patients before and after the initiation of pulmonary vasodilator. To evaluate those generalized data from patients with COPD, we evaluated multiple slices from 42 patients whose PH was not clinically suspicious. We also selected five PH patients with idiopathic interstitial pneumonia (IIP-PH) and analyzed serial changes of pulmonary artery enlargement (PA:A ratio).

RESULTS

In 42 COPD patients without PH, LAA% had a statistically significant negative correlation with %CSA <5. However, three of four COPD-PH patients manifested no such correlation. In two patients, clinical findings were dramatically improved after the initiation of pulmonary vasodilator. Notably, LAA% and %CSA <5 in those patients correlated significantly after its treatment. In COPD-PH, the PA:A ratio was significantly decreased after the initiation of pulmonary vasodilator therapy (1.25 ± 0.13 vs. 1.13 ± 0.11, p = 0.019), but not in IIP-PH.

CONCLUSIONS

Our study demonstrates that the use of quantitative CT analysis is a plausible and beneficial tool for predicting and evaluating the effect of pulmonary vasodilators in patients with COPD-PH.

Visually stratified CT honeycombing as a survival predictor in combined pulmonary fibrosis and emphysema

OBJECTIVE

To determine whether visually stratified CT findings and pulmonary function variables are helpful in predicting mortality in patients with combined pulmonary fibrosis and emphysema (CPFE).

METHODS

We retrospectively identified 113 patients with CPFE who underwent high-resolution CT between January 2004 and December 2009. The extent of emphysema and fibrosis on CT was visually assessed using a 6- or 5-point scale, respectively. Univariate and multivariate Cox proportional regression analyses were performed to determine the prognostic value of visually stratified CT findings and pulmonary function variables in patients with CPFE. Differences in 5-year survival rates in patients with CPFE according to the extent of honeycombing were calculated using Kaplan-Meier analysis.

RESULTS

An increase in the extent of visually stratified honeycombing on CT [hazard ratio (HR), 1.95; p = 0.018; 95% confidence interval (CI), 1.12-3.39] and reduced diffusing capacity of lung for carbon monoxide (DLCO) (HR, 0.97; p = 0.017; 95% CI, 0.94-0.99) were independently associated with increased mortality. In patients with CPFE, the 5-year survival rate was 78.5% for <5% honeycombing, 55.7% for 5-25% honeycombing, 32% for 26-50% honeycombing and 33.3% for >50% honeycombing on CT.

CONCLUSION

The >50% honeycombing on CT and reduced DLCO are important prognostic factors in CPFE.

ADVANCES IN KNOWLEDGE

Visual estimation of honeycombing extent on CT can help in the prediction of prognosis in CPFE.

Combined pulmonary fibrosis and emphysema (CPFE): an entity different from emphysema or pulmonary fibrosis alone

Chronic obstructive pulmonary disease (COPD) and idiopathic interstitial pneumonias (IIP), with different radiological, pathological, functional and prognostic characteristics, have been regarded as separate entities for a long time. However, there is an increasing recognition of the coexistence of emphysema and pulmonary fibrosis in individuals. The association was first described as a syndrome by Cottin in 2005, named "combined pulmonary fibrosis and emphysema (CPFE)", which is characterized by exertional dyspnea, upper-lobe emphysema and lower-lobe fibrosis, preserved lung volume and severely diminished capacity of gas exchange. CPFE is frequently complicated by pulmonary hypertension, acute lung injury and lung cancer and prognosis of it is poor. Treatments for CPFE patients with severe pulmonary hypertension are less effective other than lung transplantation. However, CPFE has not yet attracted wide attention of clinicians and there is no research systematically contrasting the differences among CPFE, emphysema/COPD and IIP at the same time. The authors will review the existing knowledge of CPFE and compare them to either entity alone for the first time, with the purpose of improving the awareness of this syndrome and exploring novel effective therapeutic strategies in clinical practice.

Quantitative CT evaluation in patients with combined pulmonary fibrosis and emphysema: correlation with pulmonary function

RATIONALE AND OBJECTIVES

The purpose of this study was to evaluate the correlations between objective quantitative computed tomography (CT) measurements of the extent of emphysematous and fibrotic lesions and the results of pulmonary function tests (PFTs) in patients with combined pulmonary fibrosis and emphysema (CPFE).

MATERIALS AND METHODS

This study involved 43 CPFE patients who underwent CT and PFTs. The extent of emphysematous lesions was obtained by calculating the percentage of low attenuation area (%LAA) values lower than -950 Hounsfield units (HU). Fibrotic lesions were defined as high attenuation area (HAA) using thresholds with pixels between 0 and -700 HU, and the extent of fibrosis was obtained by calculating the percentage of HAA (%HAA). The correlations of %LAA and %HAA with PFTs were evaluated by the Spearman rank correlation coefficients and multiple linear regression analysis.

RESULTS

A significant negative correlation was found between %HAA and diffusing capacity of the lung for carbon monoxide (DLco) %predicted (ρ = -0.747; P < .001), whereas no significant correlation was found between %LAA and DLco %predicted. On multiple linear regression analysis, although the %HAA and %LAA were independent contributors to DLco %predicted, the predictive power of %HAA was superior to that of %LAA.

CONCLUSIONS

In CPFE, the extent of fibrosis has a more significant impact on DLco than emphysema.

Combined pulmonary fibrosis and emphysema: an increasingly recognized condition

Combined pulmonary fibrosis and emphysema (CPFE) has been increasingly recognized in the literature. Patients with CPFE are usually heavy smokers or former smokers with concomitant lower lobe fibrosis and upper lobe emphysema on chest HRCT scans. They commonly present with severe breathlessness and low DLCO, despite spirometry showing relatively preserved lung volumes. Moderate to severe pulmonary arterial hypertension is common in such patients, who are also at an increased risk of developing lung cancer. Unfortunately, there is currently no effective treatment for CPFE. In this review, we discuss the current knowledge of the pathogenesis, clinical characteristics, and prognostic factors of CPFE. Given that most of the published data on CPFE are based on retrospective analysis, more studies are needed in order to address the role of emphysema and its subtypes; the progression of fibrosis/emphysema and its correlation with inflammation; treatment options; and prognosis.

Usefulness of coronal reconstruction CT images for quantitative evaluation of the cross-sectional area of small pulmonary vessels

RATIONALE AND OBJECTIVES

Cross-sectional area <5 mm(2) (CSA<5) is a computed tomography (CT) metric that has been used for the evaluation of pulmonary vessel alterations and perfusion. CSA<5 is calculated from three axial slices; thus, whether CSA<5 represents the small pulmonary vessel alterations in the whole lung remains unclear. The purpose of this study was to compare the measurements of CSA<5 using three axial slices and coronal reconstructed slices in the relationship between the measured CSA<5 and pulmonary perfusion measured using lung perfusion scintigraphy.

MATERIALS AND METHODS

This study comprised 28 subjects who underwent both noncontrast CT and lung perfusion scintigraphy. The present study measured CSA<5 using both three axial CT images and coronal reconstruction images and then obtained the percentage of the CSA in right lung to that in whole lung (R/W-CSA<5). Using anteroposterior and posteroanterior projections on technetium-99m macroaggregated albumin (MAA) lung perfusion scintigraphy, we obtained right and total lung counts and calculated the percentage of the right to whole lung counts (R/W-MAA). The correlations of the R/W-CSA<5 calculated using three axial slices (R/W-CSA(A)x<5) and coronal reconstructed slices (R/W-CSA(COR)<5) with R/W-MAA were evaluated using Spearman rank correlation analysis.

RESULTS

Both R/W-CSA(Ax)<5 and R/W-CSA(COR)<5 were significantly correlated with R/W-MAA; however, the correlation coefficient with R/W-CSA(COR)<5 (ρ = 0.842, P < .0001) was greater than that with R/W-CSA(Ax)<5 (ρ = 0.631, P = .0004).

CONCLUSIONS

Coronal reconstruction images appear suitable for quantitative measurement of CSA of small pulmonary vessels.