Shin Matsuoka

Quantitative Assessment of Air Trapping in Chronic Obstructive Pulmonary Disease Using Inspiratory and Expiratory Volumetric MDCT

OBJECTIVE The purpose of our study was to determine the attenuation threshold value for the detection and quantification of air trapping using paired inspiratory and expiratory volumetric MDCT scans and to assess whether the densitometric parameter can be used for the quantification of airway dysfunction in chronic obstructive pulmonary disease (COPD) regardless of the degree of emphysema. MATERIALS AND METHODS This study included 36 patients with COPD who underwent 64-MDCT. The entire lung volume with attenuation between -500 and -1,024 H was segmented as whole lung. The lung volume with attenuation between -500 and -950 H was segmented as limited lung, while the lung volume of less than -950 H was segmented as emphysema and eliminated. The relative volumes for limited lung (relative volume(n-950)) with attenuation values below thresholds (n) ranging from -850 to -950 H, and relative volume for whole lung (relative volume(<n)) were obtained on inspiratory and expiratory CT. Then the differences of relative volumes after expiration in whole lung (relative volume change(<n)) and limited lung (relative volume change(n-950)) were calculated. Patients were classified into two groups according to mean relative volume less than -950 H. Correlations between densitometry parameters and pulmonary function tests (PFTs) reflecting airway dysfunction were evaluated. RESULTS The highest correlation with PFTs was observed at the upper threshold of -860 H. In the moderate to severe emphysema group (relative volume(<-950) > 15%), relative volume change(860-950) significantly correlated with the results of PFTs, whereas no significant correlations were seen between relative volume change(<-860) and PFTs. In the minimal or mild emphysema group (inspiratory relative volume(<-950) < 15%), all densitometric parameters correlated with PFTs. CONCLUSION The densitometric parameter of relative volume change calculated on paired inspiratory and expiratory MDCT using the threshold of -860 H in limited lung correlated closely with airway dysfunction in COPD regardless of the degree of emphysema.

Pulmonary Hypertension and Computed Tomography Measurement of Small Pulmonary Vessels in Severe Emphysema

RATIONALE Vascular alteration of small pulmonary vessels is one of the characteristic features of pulmonary hypertension in chronic obstructive pulmonary disease. The in vivo relationship between pulmonary hypertension and morphological alteration of the small pulmonary vessels has not been assessed in patients with severe emphysema. OBJECTIVES We evaluated the correlation of total cross-sectional area of small pulmonary vessels (CSA) assessed on computed tomography (CT) scans with the degree of pulmonary hypertension estimated by right heart catheterization. METHODS In 79 patients with severe emphysema enrolled in the National Emphysema Treatment Trial (NETT), we measured CSA less than 5 mm(2) (CSA(<5)) and 5 to 10 mm(2) (CSA(5-10)), and calculated the percentage of total CSA for the lung area (%CSA(<5) and %CSA(5-10), respectively). The correlations of %CSA(<5) and %CSA(5-10) with pulmonary arterial mean pressure (Ppa) obtained by right heart catheterization were evaluated. Multiple linear regression analysis using Ppa as the dependent outcome was also performed. MEASUREMENTS AND MAIN RESULTS The %CSA(<5) had a significant negative correlation with Ppa (r = -0.512, P < 0.0001), whereas the correlation between %CSA(5-10) and Ppa did not reach statistical significance (r = -0.196, P = 0.083). Multiple linear regression analysis showed that %CSA(<5) and diffusing capacity of carbon monoxide (DL(CO)) % predicted were independent predictors of Ppa (r(2) = 0.541): %CSA (<5) (P < 0.0001), and DL(CO) % predicted (P = 0.022). CONCLUSIONS The %CSA(<5) measured on CT images is significantly correlated to Ppa in severe emphysema and can estimate the degree of pulmonary hypertension.

Airway Dimensions at Inspiratory and Expiratory Multisection CT in Chronic Obstructive Pulmonary Disease: Correlation with Airflow Limitation

PURPOSE To analyze the relationship between airflow limitation and airway dimensions from the third to the fifth generation of bronchi in patients with chronic obstructive pulmonary disease (COPD) by using inspiratory and expiratory multisection computed tomography (CT). MATERIALS AND METHODS This retrospective study was approved by the institutional review board, which waived the need for informed consent. The study included 50 patients with COPD who underwent both inspiratory and expiratory 64-detector CT. In each patient, mean values of airway luminal areas from the third to the fifth generation of three bronchi (right B1, right B10, and left B3) were measured at inspiratory CT (IA3, IA4, and IA5) and expiratory CT (EA3, EA4, and EA5). To evaluate the change of the airway luminal area between inspiration and expiration, the ratio of expiratory to inspiratory airway luminal area in each generation was calculated (EA3/IA3, EA4/IA4, and EA5/IA5). Correlations between airway dimensions and pulmonary function test results were evaluated. RESULTS The correlation coefficients between airway luminal area measured at expiratory CT and the forced expiratory volume in 1 second (FEV(1)) were higher than those for inspiratory CT and improved as the airway size decreased from the third to the fifth generation (IA3, r = .02; IA4, r = .18; IA5, r = .26; EA3, r = .09; EA4, r = .40; EA5, r = .63). EA5/IA5 had the highest correlations with FEV(1) (r = .72, P < .001). There were no significant correlations between EA3/IA3 and pulmonary function test results. CONCLUSION Airway lumen measured at expiratory CT was more closely related to expiratory airflow measurements than was lumen measured at inspiratory CT. In addition, the changes of airway luminal area between inspiration and expiration were strongly related to airflow limitation.

Quantitative CT Assessment of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is characterized by the presence of airflow limitation that is caused by a combination of small airway remodeling and emphysema-induced loss of elastic recoil. The management of COPD depends on the relative distribution and severity of these two pathologic processes, factors that may vary widely even among patients with a similar degree of airflow limitation. Standard lung function testing with spirometry is unhelpful for distinguishing the specific contribution of each process. Pathologic changes such as emphysema and modification of the small and large airways are better evaluated with quantitative analyses of image data from multidetector computed tomography (CT). CT-based quantitative analyses can help differentiate the COPD phenotype (emphysema-predominant, airway-predominant, or mixed), which is crucial information for determining the appropriate management strategy.

Identification of early interstitial lung disease in smokers from the COPDGene Study.

RATIONALE AND OBJECTIVES The aim of this study is to compare two subjective methods for the identification of changes suggestive of early interstitial lung disease (ILD) on chest computed tomographic (CT) scans. MATERIALS AND METHODS The CT scans of the first 100 subjects enrolled in the COPDGene Study from a single institution were examined using a sequential reader and a group consensus interpretation scheme. CT scans were evaluated for the presence of parenchymal changes consistent with ILD using the following scoring system: 0 = normal, 1 = equivocal for the presence of ILD, 2 = highly suspicious for ILD, and 3 = classic ILD changes. A statistical comparison of patients with early ILD to normal subjects was performed. RESULTS There was a high degree of agreement between methods (kappa = 0.84; 95% confidence interval, 0.73-0.94; P < .0001 for the sequential and consensus methods). The sequential reading method had both high positive (1.0) and negative (0.97) predictive values for a consensus read despite a 58% reduction in the number of chest CT evaluations. Regardless of interpretation method, the prevalence of chest CT changes consistent with early ILD in this subset of smokers from COPDGene varied between 5% and 10%. Subjects with early ILD tended to have greater tobacco smoke exposure than subjects without early ILD (P = .053). CONCLUSIONS A sequential CT interpretation scheme is an efficient method for the visual interpretation of CT data. Further investigation is required to independently confirm our findings and further characterize early ILD in smokers.

Vascular Enhancement and Image Quality of MDCT Pulmonary Angiography in 400 Cases: Comparison of Standard and Low Kilovoltage Settings

OBJECTIVE The purpose of this study was to investigate the vascular enhancement and image quality of pulmonary CT angiography performed with lower peak kilovoltage settings in a large patient sample. MATERIALS AND METHODS This retrospective study was approved by our institutional review board, which waived the requirement for informed consent. Four hundred patients believed to have a pulmonary embolism were studied. All patients underwent 16- or 64-MDCT with automatic tube current modulation. The 200 patients in the standard peak kilovoltage group (mean age, 57 years; range, 22-95 years) underwent MDCT at 130 or 120 kVp. The 200 patients in the low peak kilovoltage group (mean age, 56 years; range, 21-92 years) underwent MDCT at 110 or 100 kVp. Vascular enhancement was evaluated by measurement of the attenuation value in the main pulmonary artery and segmental and subsegmental arteries. Image noise was quantified by measurement of the SD of the attenuation value in the main pulmonary artery. One blinded radiologist assessed image quality using visual scores. Wilcoxons rank test was used to evaluate differences between the groups. RESULTS Mean vascular enhancement in the main pulmonary artery had significantly higher attenuation values in the low peak kilovoltage group (376.1 +/- 102.9 HU) than in the standard peak kilovoltage group (309.2 +/- 94.8 HU) (p < 0.0001). Mean attenuation values in all measured segmental and subsegmental arteries were significantly higher in the low peak kilovoltage group than in the standard peak kilovoltage group (p < 0.0001). Image noise in the low peak kilovoltage group was significantly higher than in the standard peak kilovoltage group (p < 0.0001). There was no significant difference in the image quality scores of the two groups (p = 0.116). CONCLUSION Lowering kilovoltage improved vascular enhancement without deterioration of image quality. The results of our study confirm previously reported preliminary findings.

Quantitative assessment of peripheral airway obstruction on paired expiratory/inspiratory thin-section computed tomography in chronic obstructive pulmonary disease with emphysema.

Objectives: We examined the hypothesis that paired inspiratory/expiratory computed tomography (CT) scans in a limited-lung area that excludes emphysema may provide a more accurate evaluation of peripheral airway obstruction in patients with chronic obstructive pulmonary disease (COPD) with emphysema. Materials and Methods: This study included 32 patients with COPD. The cross-sectional area between −500 and −1024 HU was segmented as whole-lung. The relative areas (RA) less than −950 HU for the whole-lung (RA<−950) were segmented as emphysema, and pixels less than −900 HU for the whole-lung (RA<−900) were segmented to evaluate air trapping. Next, the cross-sectional area between −500 and −950 HU that excludes emphysema was segmented as limited-lung, and pixels between −900 and −950 HU for the limited-lung (RA900-950) were segmented. The changes in RA<−900 (RA<−900-change) and RA900-950 (RA900-950-change) between inspiration and expiration were calculated. Correlations between CT measurements and the results of pulmonary function tests (PFT) were evaluated. Results: There was no significant difference between the mean inspiratory RA<−950 and expiratory RA<−950 (P = 0.245), but the mean expiratory RA900-950 decreased significantly compared with the mean inspiratory RA900-950 (P < 0.001). The correlation coefficients between PFT parameters and the RA900-900-change in the limited-lung without emphysema were higher than that of the RA<−900-change in the whole-lung. Conclusions: The paired inspiratory/expiratory CT measurements in the limited-lung without emphysema correlated more closely with the PFTs. Our observations suggest that paired inspiratory/expiratory CT scans in the limited-lung excluding emphysema are sensitive for the evaluation of airway obstruction in COPD with emphysema.

Quantitative CT Measurement of Cross-sectional Area of Small Pulmonary Vessel in COPD: Correlations with Emphysema and Airflow Limitation

RATIONALE AND OBJECTIVES Pulmonary vascular alteration is one of the characteristic features of chronic obstructive pulmonary disease (COPD). Recent studies suggest that vascular alteration is closely related to endothelial dysfunction and may be further influenced by emphysema. However, the relationship between morphological alteration of small pulmonary vessels and the extent of emphysema has not been assessed in vivo. The objectives of this study are: to evaluate the correlation of total cross-sectional area (CSA) of small pulmonary vessels with the extent of emphysema and airflow obstruction using CT scans and to assess the difference of total CSA between COPD phenotypes. MATERIALS AND METHODS We measured CSA less than 5 mm(2) and 5-10 mm(2), and calculated the percentage of the total CSA for the lung area (%CSA < 5, and %CSA5-10, respectively) using CT scans in 191 subjects. The extent of emphysema (%LAA-950) was calculated, and the correlations of %CSA < 5 and %CSA5-10 with %LAA-950 and results of pulmonary function tests (PFTs) were evaluated. The differences in %CSA between COPD phenotypes were also assessed. RESULTS The %CSA < 5 had significant negative correlations with %LAA-950 (r = -0.83, P < .0001). There was a weak but statistically significant correlation of %CSA < 5 with forced expiratory volume in 1 second (FEV1)% predicted (r = 0.29, P < .0001) and FEV1/forced vital capacity (r = 0.45, P < .0001). A %CSA 5-10 had weak correlations with %LAA-950 and results of PFTs. %CSA < 5 was significantly higher in bronchitis phenotype than in the emphysema phenotype (P < .0001). CONCLUSIONS Total CSA of small pulmonary vessels at sub-subsegmental levels strongly correlates with the extent of emphysema (%LAA-950) and reflects differences between COPD phenotypes.

Collapsibility of lung volume by paired inspiratory and expiratory CT scans: Correlations with lung function and mean lung density

RATIONALE AND OBJECTIVES To evaluate the relationship between measurements of lung volume (LV) on inspiratory/expiratory computed tomography (CT) scans, pulmonary function tests (PFT), and CT measurements of emphysema in individuals with chronic obstructive pulmonary disease. MATERIALS AND METHODS Forty-six smokers (20 females and 26 males; age range 46-81 years), enrolled in the Lung Tissue Research Consortium, underwent PFT and chest CT at full inspiration and expiration. Inspiratory and expiratory LV values were automatically measured by open-source software, and the expiratory/inspiratory (E/I) ratio of LV was calculated. Mean lung density (MLD) and low attenuation area percent (<-950 HU) were also measured. Correlations of LV measurements with lung function and other CT indices were evaluated by the Spearman rank correlation test. RESULTS LV E/I ratio significantly correlated with the following: the percentage of predicted value of forced expiratory volume in the first second (FEV(1)), the ratio of FEV(1) to forced vital capacity (FVC), and the ratio of residual volume (RV) to total lung capacity (TLC) (FEV(1)%P, R = -0.56, P < .0001; FEV(1)/FVC, r = -0.59, P < .0001; RV/TLC, r = 0.57, P < .0001, respectively). A higher correlation coefficient was observed between expiratory LV and expiratory MLD (r = -0.73, P < .0001) than between inspiratory LV and inspiratory MLD (r = -0.46, P < .01). LV E/I ratio showed a very strong correlation to MLD E/I ratio (r = 0.95, P < .0001). CONCLUSIONS LV E/I ratio can be considered to be equivalent to MLD E/I ratio and to reflect airflow limitation and air-trapping. Higher collapsibility of lung volume, observed by inspiratory/expiratory CT, indicates less severe conditions in chronic obstructive pulmonary disease.

Airway wall attenuation: a biomarker of airway disease in subjects with COPD.

The computed tomographic (CT) densities of imaged structures are a function of the CT scanning protocol, the structure size, and the structure density. For objects that are of a dimension similar to the scanner point spread function, CT will underestimate true structure density. Prior investigation suggests that this process, termed contrast reduction, could be used to estimate the strength of thin structures, such as cortical bone. In this investigation, we endeavored to exploit this process to provide a CT-based measure of airway disease that can assess changes in airway wall thickening and density that may be associated with the mural remodeling process in subjects with chronic obstructive pulmonary disease (COPD). An initial computer-based study using a range of simulated airway wall sizes and densities suggested that CT measures of airway wall attenuation could detect changes in both wall thickness and structure density. A second phantom-based study was performed using a series of polycarbonate tubes of known density. The results of this again demonstrated the process of contrast reduction and further validated the computer-based simulation. Finally, measures of airway wall attenuation, wall thickness, and wall area (WA) divided by total cross-sectional area, WA percent (WA%), were performed in a cohort of 224 subjects with COPD and correlated with spirometric measures of lung function. The results of this analysis demonstrated that wall attenuation is comparable to WA% in predicting lung function on univariate correlation and remain as a statistically significant correlate to the percent forced expiratory volume in 1 s predicted when adjusted for measures of both emphysema and WA%. These latter findings suggest that the quantitative assessment of airway wall attenuation may offer complementary information to WA% in characterizing airway disease in subjects with COPD.