Kunihiro Yagihashi

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.

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 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.

Correlation between airflow limitation and airway dimensions assessed by multidetector CT in asthma

BACKGROUND Asthma is characterized by variable airflow obstruction and airway wall thickening. Multidetector-row computed tomography (MDCT) is useful for the evaluation of airway wall structural changes in asthma. The objective of the study is to assess the relationship between airflow limitation and airway dimensions from the third to fifth generation bronchi in asthma using MDCT. METHODS Thirty-eight subjects with asthma underwent MDCT to measure the airway wall area (WA) and luminal area (Ai), WA and Ai corrected by body surface area (BSA), up to the fifth generation of the apical bronchus (B1) and the posterior basal bronchus (B10) of the right lung. RESULTS WA/BSA, WA percentage (WA%) and Ai/BSA in the fifth generation were significantly correlated with forced expiratory volume in 1 s (FEV(1))% predicted. The correlation coefficients between WA% and FEV(1)% predicted increased when tracking the airways from the third to the fifth generation (r=-0.25, p>0.05; r=-0.40, p<0.01; r=-0.63, p<0.001 for B1; r=-0.23, p>0.05; r=-0.47, p<0.01; r=-0.69, p<0.001 for B10). At the generation 5, WA% was greater and Ai/BSA was smaller in severe asthma than mild-to-moderate asthma. CONCLUSION These results suggest that airway flow limitation in asthma is closely related to the more distal airways (third to fifth generation).

The Clinical Course of Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia

BACKGROUND Current understanding of the clinical course of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is poor and based predominantly on small case series. In our clinical experience, we have found that the diagnosis of DIPNECH is frequently delayed because respiratory symptoms are ascribed to other lung conditions. The objectives of this study were to collect and analyze longitudinal clinical data on pulmonary physiology, chest high-resolution CT (HRCT) imaging, and therapies to better delineate the course of disease. METHODS We established a cohort of patients (N = 30) with DIPNECH seen at our institution. We used descriptive statistics to summarize cohort characteristics and longitudinal analytic techniques to model FEV1 % predicted (FEV1%) over time. RESULTS All subjects were women who presented with long-standing cough and dyspnea. The majority had an FEV1% < 50% at the time of diagnosis. Forty percent were given a diagnosis of asthma as the cause for physiologic obstruction. The mean FEV1% for the entire cohort showed no statistically significant decline over time, but 26% of the subjects experienced a 10% decline in FEV1 within 2 years. Among the pathology samples available for review, 28% (five of 18) had typical carcinoids and 44% had associated constrictive bronchiolitis. We propose clinical diagnostic criteria for DIPNECH that incorporate demographic, pulmonary physiology, HRCT imaging, and transbronchial and surgical lung biopsy data. CONCLUSIONS DIPNECH is a female-predominant lung disease manifested by dyspnea and cough, physiologic obstruction, and nodules on HRCT imaging. Additional research is needed to understand the natural history of this disease and validate the proposed diagnostic criteria.

Morphological Progression of Emphysema on Thin-section Ct: Analysis of Longitudinal Change in the Number and Size of Low-attenuation Clusters

Objectives: To evaluate morphological changes in the number and size of low-attenuation clusters on computed tomography (CT) in patients with emphysema. Materials and Methods: In 27 patients who had follow-up CT scans for 6 months or greater, initial 27 scans and follow-up 39 scans were analyzed. The number per slice (LAN/s) and mean size (LAS) of low-attenuation clusters less than -950 HU, and total low-attenuation area below -950 HU per slice (LAA-950/s) were calculated. Results: LAS and LAA-950/s were significantly increased over time. No significant correlation was found between LAN/s and follow-up period. LAS increased in 37 of 39 (95%) follow-up scans, whereas LAN/s decreased in 17 of 39 (44%) follow-up scans. Conclusions: On the morphological progression of emphysema, the mean size of low-attenuation clusters was significantly increased during the follow-up period, whereas no significant correlation was found between the number of low-attenuation clusters and follow-up period.

Quantification of Thin-Section CT Lung Attenuation in Acute Pulmonary Embolism: Correlations with Arterial Blood Gas Levels and CT Angiography

OBJECTIVE The purposes of this study were to investigate the frequency histogram of lung attenuation on CT angiography (CTA) in patients with and without acute pulmonary embolism (PE) and to evaluate the relation of the frequency histogram of lung attenuation and hypoxemia. MATERIALS AND METHODS Twenty-six patients with PE and 11 patients without PE who underwent CTA were evaluated with frequency histograms. We obtained quantitative parameters such as mean lung attenuation, median lung attenuation, SD, skewness, kurtosis, and the proportion of lung attenuation except for the median +/- 50 H (P +/- 50 H). Lung attenuation was also assessed visually and scored. The relationship between those histogram parameters, or visual score, and Pa(O2) was evaluated. CTA scores for evaluation of the degree of pulmonary artery obstruction were obtained, and the relation with Pa(O2) was assessed. RESULTS No significant differences were found in mean lung attenuation and median lung attenuation between patients with and without PE. Meanwhile, SD, skewness, kurtosis, and P +/- 50 H were significantly different between patients with and without PE (p = 0.0003, 0.0071, 0.0047, and 0.0028, respectively) and significantly correlated with Pa(O2) (r = -0.770, 0.797, 0.786, -0.871, respectively). Significant differences were found in visual scores between patients with and without PE (p < 0.0001). There were significant but relatively low correlations between CTA score and arterial blood gas levels (r = -0.442, p = 0.03). CONCLUSION In patients with acute PE, heterogeneity in lung attenuation is more prominent than in patients without PE.

MRI of Pulmonary Nodules

OBJECTIVE The purpose of this article is to review the current status of MRI for evaluation of pulmonary nodules. CONCLUSION Although clinical applications of pulmonary MRI face technical limitations, currently available MRI methods have contributed to morphologic and functional evaluations of pulmonary nodules.

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.

Idiopathic pulmonary fibrosis: Data-driven textural analysis of extent of fibrosis at baseline and 15-month follow-up

Purpose To evaluate associations between pulmonary function and both quantitative analysis and visual assessment of thin-section computed tomography (CT) images at baseline and at 15-month follow-up in subjects with idiopathic pulmonary fibrosis (IPF). Materials and Methods This retrospective analysis of preexisting anonymized data, collected prospectively between 2007 and 2013 in a HIPAA-compliant study, was exempt from additional institutional review board approval. The extent of lung fibrosis at baseline inspiratory chest CT in 280 subjects enrolled in the IPF Network was evaluated. Visual analysis was performed by using a semiquantitative scoring system. Computer-based quantitative analysis included CT histogram-based measurements and a data-driven textural analysis (DTA). Follow-up CT images in 72 of these subjects were also analyzed. Univariate comparisons were performed by using Spearman rank correlation. Multivariate and longitudinal analyses were performed by using a linear mixed model approach, in which models were compared by using asymptotic χ2 tests. Results At baseline, all CT-derived measures showed moderate significant correlation (P < .001) with pulmonary function. At follow-up CT, changes in DTA scores showed significant correlation with changes in both forced vital capacity percentage predicted (ρ = -0.41, P < .001) and diffusing capacity for carbon monoxide percentage predicted (ρ = -0.40, P < .001). Asymptotic χ2 tests showed that inclusion of DTA score significantly improved fit of both baseline and longitudinal linear mixed models in the prediction of pulmonary function (P < .001 for both). Conclusion When compared with semiquantitative visual assessment and CT histogram-based measurements, DTA score provides additional information that can be used to predict diminished function. Automatic quantification of lung fibrosis at CT yields an index of severity that correlates with visual assessment and functional change in subjects with IPF.