Low- and High-Attenuation Lung Volume in Quantitative Chest CT in Children without Lung Disease

In contrast to studies of adults with emphysema, application of fixed thresholds to determine low- and high-attenuation areas (air-trapping and parenchymal lung disease) in pediatric quantitative chest CT is problematic. We aimed to assess age effects on: (i) mean lung attenuation (full inspiration); and (ii) low and high attenuation thresholds (LAT and HAT) defined as mean attenuation and 1 SD below and above mean, respectively. Chest CTs from children aged 6–17 years without abnormalities were retrieved, and histograms of attenuation coefficients were analyzed. Eighty examinations were included. Inverse functions described relationships between age and mean lung attenuation, LAT or HAT (p < 0.0001). Predicted value for LAT decreased from −846 HU in 6-year-old to −950 HU in 13- to 17-year-old subjects (cut-off value for assessing emphysema in adults). %TLCCT with low attenuation correlated with age (rs = −0.31; p = 0.005) and was <5% for 9–17-year-old subjects. Inverse associations were demonstrated between: (i) %TLCCT with high attenuation and age (r2 = 0.49; p < 0.0001); (ii) %TLCCT with low attenuation and TLCCT (r2 = 0.47; p < 0.0001); (iii) %TLCCT with high attenuation and TLCCT (r2 = 0.76; p < 0.0001). In conclusion, quantitative analysis of chest CTs from children without lung disease can be used to define age-specific LAT and HAT for evaluation of pediatric lung disease severity.

The New Useful High-Resolution Computed Tomography Finding for Diagnosing Fibrotic Hypersensitivity Pneumonitis: “Hexagonal Pattern”: A Single-Center Retrospective Study

Background Centrilobular nodules, ground-glass opacity (GGO), mosaic attenuation, air trapping, and three-density pattern were reported as high-resolution computed tomography (HRCT) findings characteristic of fibrotic hypersensitivity pneumonitis (HP). However, it is often difficult to differentiate fibrotic HP from idiopathic pulmonary fibrosis (IPF). In fibrotic HP, the HRCT sometimes shows tortoiseshell-like interlobular septal thickening that extends from the subpleural lesion to the inner layers. This finding is called “hexagonal pattern,” and this study is focused on the possibility that such finding is useful for differentiating fibrotic HP from IPF. Methods This study included patients with multidisciplinary discussion (MDD) diagnosis of fibrotic HP or IPF undergoing surgical lung biopsy between January 2015 and December 2017 in Kanagawa Cardiovascular and Respiratory Center. Two radiologists have evaluated the HRCT findings without clinical and pathological information. Results A total of 23 patients were diagnosed with fibrotic HP by MDD and 48 with IPF. Extensive GGO, centrilobular nodules, and hexagonal pattern were more frequent findings in fibrotic HP than in IPF. No significant difference was observed between the two groups in the presence or absence of mosaic attenuation, air trapping, or three-density pattern. In the multivariate logistic regression, the presence of extensive GGO and hexagonal pattern was associated with increased odds ratio of fibrotic HP. The sensitivity and specificity of the diagnosis of fibrotic HP in the presence of the hexagonal pattern were 69.6% and 87.5%, respectively. Conclusion Hexagonal pattern is a useful finding for differentiating fibrotic HP from IPF.

Air entrapment and its effect on pressure impulses in the slamming of a flat disc on water

The presence of ambient air in liquid-slamming events plays a crucial role in influencing the shape of the liquid surface prior to the impact, and the distribution of loads created upon impact. We study the effect of trapped air on impact loads in a simplified geometry, by slamming a horizontal flat disc onto a stationary water bath at a well-controlled velocity. We show how air trapping influences pressure peaks at different radial locations on the disc, how the pressure impulses are affected and how local pressure impulses differ from those obtained from area-integrated (force) impulses at impact. More specifically, we find that the air layer causes a gradual buildup of the load before the peak value is reached, and show that this buildup follows inertial scaling. Further, the same localised pressure impulse at the disc centre is found to be lower than the corresponding (area-integrated) force impulse on the entire disc. While the (area-integrated) force impulses are close to the classical result of Batchelor (An Introduction to Fluid Dynamics, Cambridge University Press, 1967, § 6.10) and Glasheen & McMahon (Phys. Fluids, vol. 8, issue 8, 1996, pp. 2078–2083), the localised pressure impulses at the disc centre, where the trapped air layer is at its thickest, lie closer to the theoretical estimation by Peters et al. (J. Fluid Mech., vol. 724, 2013, pp. 553–580) for an air-cushioned impact.

A Preliminary Study on the Relationship Between High-resolution Computed Tomography and Lung Function in People at Risk of Developing Chronic Obstructive Pulmonary Disease

Background: There is high morbidity and mortality for patients with chronic obstructive pulmonary disease (COPD) in China. The aim of our study was to explore the differences in high-resolution computed tomography (HRCT) emphysema parameters, air trapping parameters, and lung density parameters between patients at high risk and low risk of developing COPD and evaluate their correlation with lung function indicators.Methods: In this retrospective, single-center cohort study, we enrolled outpatients from the Physical Examination Center and Respiratory Medicine of The First Affiliated Hospital of Wenzhou Medical University. The patients at risk of developing COPD were ≥40 years-old, had chronic cough or sputum production, and/or had exposure to risk factors for the disease and had not reached the diagnostic criteria. Patients were divided into a low-risk group and high-risk group according to FEV1/FVC≥80% and 80%>FEV1/FVC≥70%. The data on clinical characteristics, clinical symptom score, lung function, and HRCT were recorded.Results: 72 COPD high-risk patients and 86 COPD low-risk patients were enrolled in the study, and the air trapping index of the left, right, and bilateral lungs of the high-risk group were significantly higher than those of the low-risk group . Additionally, the mean lung density during expiration was significantly lower than that of the low-risk group. The emphysema index of left, right, and bilateral lungs was negatively correlated with FEV1/FVC (correlation coefficients were -0.33-0.22-0.26). There was a negative correlation between the air trapping index of left and right lungs and bilateral lungs and FEV1/FVC(correlation coefficients were -0.33-0.23-0.28, respectively), and the mean expiratory lung density of left and right lungs and bilateral lungs was positively correlated with FEV1/FVC (correlation coefficients were 0.31, 0.25, 0.29, respectively).Conclusions: The air trapping index and the mean expiratory lung density obtained by HRCT combined with post-processing technology can be used as a basis for distinguishing between people at high risk and low risk for developing COPD. Emphysema index, air trapping index, and mean expiratory lung density shows significantly negative correlation with FEV1/FVC, and this can be used to assess the pulmonary function status of people at risk of developing COPD.