Expiratory Scans Research Articles

The first Japanese case of autosomal dominant cutis laxa with a frameshift mutation in exon 30 of the elastin gene complicated by small airway disease with 8 years of follow-up

BackgroundCutis laxa constitutes a diverse group of connective tissue diseases, both inherited and acquired, characterized by loose skin and varying systemic involvement, including pulmonary lesions. While cutis laxa has been linked to conditions like emphysema, asthma, and bronchiectasis, the specific pathological and radiological characteristics underlying pulmonary complications related to cutis laxa remain unclear.Case presentationA 36-year-old woman, diagnosed with cutis laxa at birth, presented to our outpatient clinic with severe obstructive ventilatory impairment, evident in pulmonary function tests (expiratory volume in one second (FEV1)/forced vital capacity (FVC): 34.85%; %residual volume [RV]: 186.5%; %total lung capacity [TLC]: 129.2%). Pulmonary function tests also indicated small airway disease (%FEF50%, 7.9%; %FEF75%, 5.7%; and %FEF25–75%, 6.8%). Computed tomography (CT) revealed the lack of normal increase in lung attenuation on expiratory CT scan, with no discernible emphysematous changes. Exome sequencing was performed to confirm the association between the pulmonary lesions and cutis laxa, revealing a frameshift variant in exon 30 of the elastin gene (ELN). Further analysis employing a parametric response map revealed a longitudinal increase in the percentage of functional small airway disease (fSAD) from 37.84% to 46.61% over the 8-year follow-up, despite the absence of overt changes in CT findings, specifically the lack of normal increase in lung attenuation on expiratory CT scan. Over the same follow-up interval, there was a modest reduction of 25.6 mL/year in FEV1 coupled with a significant increase in %RV. Pulmonary function test metrics, reflective of small airway disease, exhibited a continual decline; specifically, %FEF50%, %FEF75%, and %FEF25–75% diminished from 7.9% to 7.0%, 5.7% to 4.6%, and 6.8% to 5.4%, respectively.ConclusionsThis case highlighted an instance of autosomal dominant cutis laxa arising from a frameshift variant in exon 30 of ELN, accompanied by small airway disease. Comprehensive investigation, utilizing quantitative CT analysis, revealed a longitudinal increase in fSAD percentage with a mild reduction in FEV1. These findings indicate that elastin deficiency may not only diminish elastic fibers in the skin but also be implicated in small airway disease by impacting components of the extracellular matrix in the lungs.

Predicting Acute Exacerbation Phenotype in Chronic Obstructive Pulmonary Disease Patients Using VGG-16 Deep Learning.

Exacerbations of chronic obstructive pulmonary disease (COPD) have a significant impact on hospitalizations, morbidity, and mortality of patients. This study aimed to develop a model for predicting acute exacerbation in COPD patients (AECOPD) based on deep-learning (DL) features. We performed a retrospective study on 219 patients with COPD who underwent inspiratory and expiratory HRCT scans. By recording the acute respiratory events of the previous year, these patients were further divided into non-AECOPD group and AECOPD group according to the presence of acute exacerbation events. Sixty-nine quantitative CT (QCT) parameters of emphysema and airway were calculated by NeuLungCARE software, and 2,000 DL features were extracted by VGG-16 method. The logistic regression method was employed to identify AECOPD patients, and 29 patients of external validation cohort were used to access the robustness of the results. The model 3-B achieved an area under the receiver operating characteristic curve (AUC) of 0.933 and 0.865 in the testing cohort and external validation cohort, respectively. Model 3-I obtained AUC of 0.895 in the testing cohort and AUC of 0.774 in the external validation cohort. Model 7-B combined clinical characteristics, QCT parameters, and DL features achieved the best performance with an AUC of 0.979 in the testing cohort and demonstrating robust predictability with an AUC of 0.932 in the external validation cohort. Likewise, model 7-I achieved an AUC of 0.938 and 0.872 in the testing cohort and external validation cohort, respectively. DL features extracted from HRCT scans can effectively predict acute exacerbation phenotype in COPD patients.

Expiratory Venous Volume and Arterial Tortuosity are Associated with Disease Severity and Mortality Risk in Patients with COPD: Results from COSYCONET.

The aim of this study was to evaluate the association between computed tomography (CT) quantitative pulmonary vessel morphology and lung function, disease severity, and mortality risk in patients with chronic obstructive pulmonary disease (COPD). Participants of the prospective nationwide COSYCONET cohort study with paired inspiratory-expiratory CT were included. Fully automatic software, developed in-house, segmented arterial and venous pulmonary vessels and quantified volume and tortuosity on inspiratory and expiratory scans. The association between vessel volume normalised to lung volume and tortuosity versus lung function (forced expiratory volume in 1 sec [FEV1]), air trapping (residual volume to total lung capacity ratio [RV/TLC]), transfer factor for carbon monoxide (TLCO), disease severity in terms of Global Initiative for Chronic Obstructive Lung Disease (GOLD) group D, and mortality were analysed by linear, logistic or Cox proportional hazard regression. Complete data were available from 138 patients (39% female, mean age 65 years). FEV1, RV/TLC and TLCO, all as % predicted, were significantly (p < 0.05 each) associated with expiratory vessel characteristics, predominantly venous volume and arterial tortuosity. Associations with inspiratory vessel characteristics were absent or negligible. The patterns were similar for relationships between GOLD D and mortality with vessel characteristics. Expiratory venous volume was an independent predictor of mortality, in addition to FEV1. By using automated software in patients with COPD, clinically relevant information on pulmonary vasculature can be extracted from expiratory CT scans (although not inspiratory scans); in particular, expiratory pulmonary venous volume predicted mortality. NCT01245933.

LungViT: Ensembling Cascade of Texture Sensitive Hierarchical Vision Transformers for Cross-Volume Chest CT Image-to-Image Translation.

Chest computed tomography (CT) at inspiration is often complemented by an expiratory CT to identify peripheral airways disease. Additionally, co-registered inspiratory-expiratory volumes can be used to derive various markers of lung function. Expiratory CT scans, however, may not be acquired due to dose or scan time considerations or may be inadequate due to motion or insufficient exhale; leading to a missed opportunity to evaluate underlying small airways disease. Here, we propose LungViT- a generative adversarial learning approach using hierarchical vision transformers for translating inspiratory CT intensities to corresponding expiratory CT intensities. LungViT addresses several limitations of the traditional generative models including slicewise discontinuities, limited size of generated volumes, and their inability to model texture transfer at volumetric level. We propose a shifted-window hierarchical vision transformer architecture with squeeze-and-excitation decoder blocks for modeling dependencies between features. We also propose a multiview texture similarity distance metric for texture and style transfer in 3D. To incorporate global information into the training process and refine the output of our model, we use ensemble cascading. LungViT is able to generate large 3D volumes of size 320×320×320 . We train and validate our model using a diverse cohort of 1500 subjects with varying disease severity. To assess model generalizability beyond the development set biases, we evaluate our model on an out-of-distribution external validation set of 200 subjects. Clinical validation on internal and external testing sets shows that synthetic volumes could be reliably adopted for deriving clinical endpoints of chronic obstructive pulmonary disease.

Children with severe asthma have substantial structural airway changes on computed tomography.

In adults with severe asthma (SA) bronchial wall thickening, bronchiectasis and low attenuation regions (LAR) have been described on chest computed tomography (CT) scans. The extent to which these structural abnormalities are present in children with SA is largely unknown. Our aim was to study the presence and extent of airway abnormalities on chest CT of children with SA. 161 inspiratory and expiratory CT scans, either spirometer-controlled or technician-controlled, obtained in 131 children with SA (mean±SD age 11.0±3.8 years) were collected retrospectively. Inspiratory scans were analysed manually using a semi-quantitative score and automatically using LungQ (v2.1.0.1; Thirona B.V., Nijmegen, the Netherlands). LungQ segments the bronchial tree, identifies the generation for each bronchus-artery (BA) pair and measures the following BA dimensions: outer bronchial wall diameter (Bout), adjacent artery diameter (A) and bronchial wall thickness (Bwt). Bronchiectasis was defined as Bout/A ≥1.1, bronchial wall thickening as Bwt/A ≥0.14. LAR, reflecting small airways disease (SAD), was measured automatically on inspiratory and expiratory scans and manually on expiratory scans. Functional SAD was defined as FEF25-75 and/or FEF75 z-scores <-1.645. Results are shown as median and interquartile range. Bronchiectasis was present on 95.8% and bronchial wall thickening on all CTs using the automated method. Bronchiectasis was present on 28% and bronchial wall thickening on 88.8% of the CTs using the manual semi-quantitative analysis. The percentage of BA pairs defined as bronchiectasis was 24.62% (12.7-39.3%) and bronchial wall thickening was 41.7% (24.0-79.8%) per CT using the automated method. LAR was observed on all CTs using the automatic analysis and on 82.9% using the manual semi-quantitative analysis. Patients with LAR or functional SAD had more thickened bronchi than patients without. Despite a large discrepancy between the automated and the manual semi-quantitative analysis, bronchiectasis and bronchial wall thickening are present on most CT scans of children with SA. SAD is related to bronchial wall thickening.

Application and Interpretation of High-Resolution Computed Tomography for the Diagnosis of Interstitial Lung Disease (ILD): ILD Protocol

Interstitial lung disease (ILD) encompasses a heterogeneous group of over 200 diffuse parenchymal lung diseases. Accurate diagnosis of ILD is essential for appropriate treatment but can be challenging to achieve. For patients with suspected ILD, high-resolution computed tomography (HRCT) is a minimally invasive approach that allows for convenient repeat imaging. Compared to a conventional computed tomography (CT) protocol, the HRCT protocol for ILD patients involves two additional series with different technical requirements: a prone inspiration scan, and a supine expiration scan. The prone scan is useful when dependent opacification is observed on a supine chest CT scan. It facilitates the diagnosis of honeycombing, reducing observer variation in diagnosing idiopathic pulmonary fibrosis. The expiratory scan is useful for identifying air trapping, which is essential for the diagnosis of hypersensitivity pneumonitis. It is used to assess the three-density sign, which is specific for hypersensitivity pneumonitis and characterized by patchy distribution of normal-appearing lobules, ground glass opacities, and lobules with reduced lung density and vessel size. The HRCT ILD protocol should be performed regularly to assess changes in the extent of fibrosis and to diagnose lung cancer or acute exacerbation when clinically indicated.

PhysVENeT: a physiologically-informed deep learning-based framework for the synthesis of 3D hyperpolarized gas MRI ventilation

Functional lung imaging modalities such as hyperpolarized gas MRI ventilation enable visualization and quantification of regional lung ventilation; however, these techniques require specialized equipment and exogenous contrast, limiting clinical adoption. Physiologically-informed techniques to map proton (1H)-MRI ventilation have been proposed. These approaches have demonstrated moderate correlation with hyperpolarized gas MRI. Recently, deep learning (DL) has been used for image synthesis applications, including functional lung image synthesis. Here, we propose a 3D multi-channel convolutional neural network that employs physiologically-informed ventilation mapping and multi-inflation structural 1H-MRI to synthesize 3D ventilation surrogates (PhysVENeT). The dataset comprised paired inspiratory and expiratory 1H-MRI scans and corresponding hyperpolarized gas MRI scans from 170 participants with various pulmonary pathologies. We performed fivefold cross-validation on 150 of these participants and used 20 participants with a previously unseen pathology (post COVID-19) for external validation. Synthetic ventilation surrogates were evaluated using voxel-wise correlation and structural similarity metrics; the proposed PhysVENeT framework significantly outperformed conventional 1H-MRI ventilation mapping and other DL approaches which did not utilize structural imaging and ventilation mapping. PhysVENeT can accurately reflect ventilation defects and exhibits minimal overfitting on external validation data compared to DL approaches that do not integrate physiologically-informed mapping.

EPS1.01 Using lateral decubitus computed tomography (CT) to monitor structural lung disease in young children with cystic fibrosis

Objectives: Cystic fibrosis (CF) structural lung disease is monitored using chest computed tomography scans (cCTs) during breath-hold commands. In non-compliant children, cCTs are performed either by free breathing or using a pressure-controlled protocol under general anesthesia, both resulting in expiratory scans near FRC and not residual volume (RV). cCTs taken in lateral decubitus position is thought to result in expiratory scans near RV despite free breathing, due to compression of the lung. We aimed to evaluate the feasibility and sensitivity of lateral decubitus CT to detect structural lung disease in preschool children with CF.

MR imaging of the airways.

The need for airway imaging is defined by the limited sensitivity of common clinical tests like spirometry, lung diffusion (DLCO) and blood gas analysis to early changes of peripheral airways and to inhomogeneous regional distribution of lung function deficits. Therefore, X-ray and computed tomography (CT) are frequently used to complement the standard tests.As an alternative, magnetic resonance imaging (MRI) offers radiation-free lung imaging, but at lower spatial resolution. Non-contrast enhanced MRI shows healthy airways down to the first subsegmental level/4th order (CT: eighth). Bronchiectasis can be identified by wall thickening and fluid accumulation. Smaller airways become visible, when altered by peribronchiolar inflammation or mucus retention (tree-in-bud sign).The strength of MRI is functional imaging. Dynamic, time-resolved MRI directly visualizes expiratory airway collapse down to the lobar level (CT: segmental level). Obstruction of even smaller airways becomes visible as air trapping on the expiratory scans. MRI with hyperpolarized noble gases (3He, 129Xe) directly shows the large airways and peripheral lung ventilation. Dynamic contrast-enhanced MRI (DCE MRI) indirectly shows airway dysfunction as perfusion deficits resulting from hypoxic vasoconstriction of the dependent lung volumes. Further promising scientific approaches such as non-contrast enhanced, ventilation-/perfusion-weighted MRI from periodic signal changes of respiration and blood flow are in development.In summary, MRI of the lungs and airways excels with its unique combination of morphologic and functional imaging capacities for research (e.g., in chronic obstructive lung disease or asthma) as well as for clinical imaging (e.g., in cystic fibrosis).

Pilot study to determine whether reduced-dose photon-counting detector chest computed tomography can reliably display Brody II score imaging findings for children with cystic fibrosis at radiation doses that approximate radiographs.

The Brody II score uses chest CT to guide therapeutic changes in children with cystic fibrosis; however, patients and providers are often reticent to undergo chest CT given concerns about radiation. We sought to determine the ability of a reduced-dose photon-counting detector (PCD) chest CT protocol to reproducibly display pulmonary disease severity using the Brody II score for children with cystic fibrosis (CF) scanned at radiation doses similar to those of a chest radiograph. Pediatric patients with CF underwent non-contrast reduced-dose chest PCD-CT. Volumetric inspiratory and expiratory scans were obtained without sedation or anesthesia. Three pediatric radiologists with Certificates of Added Qualification scored each scan on an ordinal scale and assigned a Brody II score to grade bronchiectasis, peribronchial thickening, parenchymal opacity, air trapping and mucus plugging. We report image-quality metrics using descriptive statistics. To calculate inter-rater agreement for Brody II scoring, we used the Krippendorff alpha and intraclass correlation coefficient (ICC). Fifteen children with CF underwent reduced-dose PCD chest CT in both inspiration and expiration (mean age 8.9years, range, 2.5-17.5years; 4 girls). Mean volumetric CT dose index (CTDIvol) was 0.07 ± 0.03mGy per scan. Mean effective dose was 0.12 ± 0.04mSv for the total examination. All three readers graded spatial resolution and noise as interpretable on lung windows. The average Brody II score was 12.5 (range 4-19), with moderate inter-reader reliability (ICC of 0.61 [95% CI=0.27, 0.84]). Inter-rater reliability was moderate to substantial for bronchiectasis (0.52), peribronchial thickening (0.55), presence of opacity (0.62) and air trapping (0.70) and poor for mucus plugging (0.09). Reduced-dose PCD-CT permits diagnostic image quality and reproducible identification of Brody II scoring imaging findings at radiation doses similar to those for chest radiography.

Computed tomography findings in bronchial asthma: quantification of air trapping and correlation with pulmonary function tests.

High-resolution computed tomography (HRCT) scans can help identify subsets of asthma patients who show rapid decline in lung function. To evaluate high-resolution computed tomography (HRCT) findings in adult patients with asthma, obtain quantitative measurements of air trapping on expiratory scans, and correlate the findings with pulmonary function tests (PFTs). Thirty adults with asthma with persistent-mild, persistent-moderate, and persistent-severe categories as per standard clinical guidelines were evaluated with inspiratory and expiratory HRCT for various imaging features of bronchial asthma. Expiratory HRCT scan were used to quantify degree of air-trapping, and their values quantified as "pixel index," using a special "density' mask" software. Complete spirometry and body plethysmography were performed on each patient within 0-2 days of HRCT scans. HRCT findings were correlated with the clinical severity groups and the CT pixel indices (PI) were correlated with the PFT results using correlation coefficients and linear regression analysis. The inspiratory CT findings did not correlate with increase in disease severity. Expiratory scans accurately quantified areas of air trapping. CT-PI correlated well with PFT values indicative of airway obstruction and airflow limitation, which helped differentiate patients with asthma with increasing severity from those with milder forms of the disease. Expiratory thin-section CT is a useful objective method to quantify air-trapping in people with asthma. The air-trapping score measured in "pixel indices" correlates well with PFT results and can successfully identify patients with severe asthma. Further studies are needed to confirm if this parameter can serve as a potential marker for airway remodeling and declining lung function.

HRCT findings in secondhand smokers with respiratory symptoms.

The present study aims to investigate the occurrence and severity of HRCT abnormalities in symptomatic never-smokers, passively exposed to cigarette smoke. A total of 135 never-smokers with respiratory symptoms, without underlying lung disease, underwent paired inspiratory-expiratory HRCT and completed the secondhand smoking (SHS) exposure scale questionnaire. Individuals passively exposed to tobacco consisted the secondhand smoking group (SHS group) (n = 68); the remaining 67 controls were never exposed to SHS. Statistical analysis was performed using the Kolmogorov-Smirnov, x2 and Pearson Point-Biserial correlation tests. P < 0.05 was statistically significant. HRCT findings in SHS group included bronchial wall thickening (98.5%), mild cylindrical bronchiectasis (44%), ground-glass opacities (17.6%), and mosaic attenuation pattern (53%). Air trapping occurred in 65% of expiratory scans. Differences in occurrence of findings between SHS group participants and controls were statistically significant (p < 0.0001). There was significant correlation between exposure to tobacco smoke in hours/day and in number of cigarettes/day and the presence of mosaic attenuation pattern, ground-glass opacities, cylindrical bronchiectasis and air trapping, respectively (p < 0.05). Cumulative SHS exposure in years was also strongly correlated with the presence of ground-glass opacities, mosaic attenuation pattern, cylindrical bronchiectasis, and air trapping, as well as with the frequency of respiratory symptoms (p < 0.05). HRCT findings attributed to SHS are mostly related to airway involvement and are correlated with the duration and grade of exposure to environmental tobacco smoke. SHS followed by lifestyle adjustments should be considered in symptomatic non-smokers with such HRCT findings.

Expiratory CT scanning in COVID-19 patients: can we add useful data?

ABSTRACTObjective:To evaluate small airway disease in COVID-19 patients using the prevalence of air trapping (AT) and correlating it with clinical outcomes. The relationship between CT-based opacities in small blood vessels and ventilation in patients with SARS-CoV-2 pneumonia was also assessed. Methods:We retrospectively included 53 patients with positive RT-PCR results for SARS-CoV-2 between March and April of 2020. All subjects underwent HRCT scanning, including inspiratory and expiratory acquisitions. Subjects were divided into two groups based on visual identification of AT. Small blood vessel volumes were estimated by means of cross-sectional areas < 5 mm2 (BV5) derived from automated segmentation algorithms. Mixed-effect models were obtained to represent the BV5 as a function of CT-based lobar opacities and lobar ventilation. Results:Of the 53 participants, AT was identified in 23 (43.4%). The presence of AT was associated with increased SpO2 at admission (OR = 1.25; 95% CI, 1.07-1.45; p = 0.004) and reduced D-dimer levels (OR = 0.99; 95% CI, 0.99-0.99; p = 0.039). Patients with AT were less likely to be hospitalized (OR = 0.27; 95% CI, 0.08-0.89; p = 0.032). There was a significant but weak inverse correlation between BV5 and CT-based lobar opacities (R2 = 0.19; p = 0.03), as well as a nonsignificant and weak direct correlation between BV5 and lobar ventilation (R2 = 0.08; p = 0.54).Conclusions:AT is a common finding in patients with COVID-19 that undergo expiratory CT scanning. The presence of AT may correlate with higher SpO2 at admission, lower D-dimer levels, and fewer hospitalizations when compared with absence of AT. Also, the volume of small pulmonary vessels may negatively correlate with CT opacities but not with lobar ventilation.

Dynamic PEEP Study: A Non-invasive Diagnostic Exam to Assess for Effective PEEP in Children with Severe BPD.

Tracheobronchomalacia (TBM) is common in neonates with bronchopulmonary dysplasia (BPD) and is associated with higher morbidity. This study evaluates the value of a CT protocol to assess the degree of TBM and gauge the adequacy of prescribed PEEP. Four infants with severe BPD on invasive mechanical ventilation underwent a chest CT protocol, including limited reduced-dose expiratory scans with varying PEEP levels. Baseline PEEP was adjusted in all subjects after performing the Dynamic PEEP CT. In two infants, the PEEP was increased due to significant TBM and in the other two without signs of TBM PEEP was decreased. The clinical course improved in all patients after adjusting PEEP. A "Dynamic PEEP" study may be reliable and non-invasive imaging modality for the evaluation of adequate ventilator settings in infants with severe BPD who are not optimal candidates for bronchoscopy.

Potential Value of Expiratory CT in Quantitative Assessment of Pulmonary Vessels in COPD.

Objective: To investigate the associations between intrapulmonary vascular volume (IPVV) depicted on inspiratory and expiratory CT scans and disease severity in COPD patients, and to determine which CT parameters can be used to predict IPVV.Methods: We retrospectively collected 89 CT examinations acquired on COPD patients from an available database. All subjects underwent both inspiratory and expiratory CT scans. We quantified the IPVV, airway wall thickness (WT), the percentage of the airway wall area (WA%), and the extent of emphysema (LAA%−950) using an available pulmonary image analysis tool. The underlying relationship between IPVV and COPD severity, which was defined as mild COPD (GOLD stage I and II) and severe COPD (GOLD stage III and IV), was analyzed using the Student's t-test (or Mann-Whitney U-test). The correlations of IPVV with pulmonary function tests (PFTs), LAA%−950, and airway parameters for the third to sixth generation bronchus were analyzed using the Pearson or Spearman's rank correlation coefficients and multiple stepwise regression.Results: In the subgroup with only inspiratory examinations, the correlation coefficients between IPVV and PFT measures were −0.215 ~ −0.292 (p < 0.05), the correlation coefficients between IPVV and WT3−6 were 0.233 ~ 0.557 (p < 0.05), and the correlation coefficient between IPVV and LAA%−950 were 0.238 ~ 0.409 (p < 0.05). In the subgroup with only expiratory scan, the correlation coefficients between IPVV and PFT measures were −0.238 ~ −0.360 (p < 0.05), the correlation coefficients between IPVV and WT3−6 were 0.260 ~ 0.566 (p < 0.05), and the correlation coefficient between IPVV and LAA%−950 were 0.241 ~ 0.362 (p < 0.05). The multiple stepwise regression analyses demonstrated that WT were independently associated with IPVV (P < 0.05).Conclusion: The expiratory CT scans can provide a more accurate assessment of COPD than the inspiratory CT scans, and the airway wall thickness maybe an independent predictor of pulmonary vascular alteration in patients with COPD.

Influence of breathing state on the accuracy of automated patient positioning in thoracic CT using a 3D camera for body contour detection

ObjectiveTo assess the influence of breathing state on the accuracy of a 3D camera for body contour detection and patient positioning in thoracic CT.Materials and methodsPatients who underwent CT of the thorax with both an inspiratory and expiratory scan were prospectively included for analysis of differences in the ideal table height at different breathing states. For a subgroup, an ideal table height suggestion based on 3D camera images at both breathing states was available to assess their influence on patient positioning accuracy. Ideal patient positioning was defined as the table height at which the scanner isocenter coincides with the patient’s isocenter.ResultsThe mean (SD) difference of the ideal table height between the inspiratory and the expiratory breathing state among the 64 included patients was 10.6 mm (4.5) (p < 0.05). The mean (SD) positioning accuracy, i.e., absolute deviation from the ideal table height, within the subgroup (n = 43) was 4.6 mm (7.0) for inspiratory scans and 7.1 mm (7.7) for expiratory scans (p < 0.05) when using corresponding 3D camera images. The mean (SD) accuracy was 14.7 mm (7.4) (p < 0.05) when using inspiratory camera images on expiratory scans; vice versa, the accuracy was 3.1 mm (9.5) (p < 0.05).ConclusionA 3D camera allows for accurate and precise patient positioning if the camera image and the subsequent CT scan are acquired in the same breathing state. It is recommended to perform an expiratory planning image when acquiring a thoracic CT scan in both the inspiratory and expiratory breathing state.Key Points• A 3D camera for body contour detection allows for accurate and precise patient positioning if the camera image and the subsequent CT scan are acquired in the same breathing state.• It is recommended to perform an expiratory planning image when acquiring a thoracic CT scan in both the inspiratory and expiratory breathing state.

The Enhanced Value of Parameter Response Mapping in a One-Stop CT Scanning: Predicting Pulmonary Function Test with Machine Learning

Background: To evaluate the performance of a machine learning approach to predict pulmonary function test (PFT) result from parameter response mapping (PRM), which enhances the value of one-stop CT scanning. Methods: 615 subjects with PFT and paired inspiratory and expiratory chest CT scanning were enrolled retrospectively, and classified into normal group, high risk group and COPD group based on PFT. 72 PRM-derived quantitative parameters including volume (cc) and volume percentage (%) of emphysema, functional-small airways disease (fSAD), and normal lung tissue (Normal) were acquired. Random forest regression model was constructed and tested on the aspect of PFT prediction, and the classification performance based on these PFT predictions was further evaluated. Findings: The machine-learning model based on PRM parameters showed good performance to predict PFT, with a coefficient of determination (R2) of 0·749 and 0·792 for FEV1/FVC and FEV1% regression respectively. The sensitivity, specificity, and accuracy for differentiating normal group from high-risk group were 0·85, 0·90 and 0·88, respectively; and 0·89, 1 and 0·99, respectively, for differentiating non-COPD group from COPD group. Interpretation: A machine learning model based on CT-derived PRM parameters could enhance the clinical value of one-stop chest CT scanning by predicting PFT results. The technique has the potential to benefit patients in clinical practice, especially for those with difficulty to perform PFT. Funding Statement: This work was supported by the National Natural Science Foundation of China [grant number 81871321, 81930049]; the National Key R&D Program of China [grant number 2016YFE0103000, 2017YFC1308703]. Declaration of Interests: None. Ethics Approval Statement: This study was approved by the hospital ethics committee and the informed consent of patients was waived.

Diaphragmatic excursion: Quantitative measure to assess adequacy of expiratory phase CT chest images

ObjectiveTo evaluate diaphragmatic excursion as a quantitative metric for change in lung volume between inspiratory and expiratory chest computed tomography (CT) images. MethodsA 12-month retrospective review identified 226 chest CT exams with inspiratory and expiratory phase imaging, 63 in individuals referred with diagnosis of asthma by ICD9/10 code. Exams acquired in the supine position at 1.25 mm slice thickness in each phase were included (n = 30, mean age = 62, M = 15, F = 15). Diaphragmatic excursion was calculated as the difference between axial slices through the lungs on inspiration and expiration, using the lung apex as the cranial bound, and the hemidiaphragm caudally. Inspiratory and expiratory lung and tracheal volumes were calculated through volumetric segmentation. Tracheal morphology was assessed at 1 cm above the level of the aortic arch, and 1 cm above the carina. ResultsInspiratory and expiratory lung volumes were higher in men (mean I = 5 + 1.6 L, E = 3.1 + 1.2 L) than women (mean I = 3.6 + 0.8 L, E = 2.4 + 0.7 L), p = .005 and p = .047, respectively. Average inspiratory and expiratory tracheal volumes were higher in men (I = 61 + 17 mL, E = 43 + 14) than women (I = 44 + 14, E = 30 + 8), p = .006 and p = .005. Average change in lung and tracheal volume between inspiratory and expiratory scans did not significantly differ between men and women. Average diaphragmatic excursion was 2.5 cm between inspiratory and expiratory scans (2.7 cm in men, 2.3 cm in women; p = .5). There was a strong positive correlation between diaphragmatic excursion and change in lung (r = .84) and tracheal volume (r = .79). A moderate correlation was also found between change in tracheal volume and change in lung volume (r = 0.67). Change in tracheal morphology between inspiratory and expiratory imaging was associated with change in tracheal volume at both 1 cm above the aortic arch (p = .04) and 1 cm above the carina (p = .008); there was no association with diaphragmatic excursion or lung volume. ConclusionsDiaphragmatic excursion is a quantitative measure of expiratory effort as validated by both lung and tracheal volumes in asthma patients, and may be more accurate than qualitative assessment based on tracheal morphology.

Common pulmonary computed tomography signs and their clinical relevance: A review

Abstract With the advent of computed tomography (CT) in respiratory medicine, a greater delineation of the respiratory structures has been possible in the two-dimensional space. The various CT techniques used by pulmonologists include the high-resolution computed tomography (HRCT) thorax with expiratory scans, contrast-enhanced CT (CECT) thorax, CT thorax, CT pulmonary angiography (CTPA) and rarely a CT aortography/angiography. Each of the imaging techniques presents stronger and weaker points. In this paper, radiological lesions are classified according to their location. Such abnormalities are observed in the airways, in the lung parenchyma, in the interstitium and last but not least in the pleura. The review mainly addresses radiological lesions with higher specificity because they are key elements in establishing a definitive diagnosis. In conclusion, performing a chest CT is vital in the diagnosis and management of respiratory conditions.

Quantitative CT-based image registration metrics provide different ventilation and lung motion patterns in prone and supine positions in healthy subjects

BackgroundPrevious studies suggested that the prone position (PP) improves oxygenation and reduces mortality among patients with acute respiratory distress syndrome (ARDS). However, the mechanism of this clinical benefit of PP is not completely understood. The aim of the present study was to quantitatively compare regional characteristics of lung functions in the PP with those in the supine position (SP) using inspiratory and expiratory computed tomography (CT) scans.MethodsNinety subjects with normal pulmonary function and inspiration and expiration CT images were included in the study. Thirty-four subjects were scanned in PP, and 56 subjects were scanned in SP. Non-rigid image registration-based inspiratory-expiratory image matching assessment was used for regional lung function analysis. Tissue fractions (TF) were computed based on the CT density and compared on a lobar basis. Three registration-derived functional variables, relative regional air volume change (RRAVC), volumetric expansion ratio (J), and three-dimensional relative regional displacement (s*) were used to evaluate regional ventilation and deformation characteristics.ResultsJ was greater in PP than in SP in the right middle lobe (P = 0 .025), and RRAVC was increased in the upper and right middle lobes (P < 0.001). The ratio of the TF on inspiratory and expiratory scans, J, and RRAVC at the upper lobes to those at the middle and lower lobes and that ratio at the upper and middle lobes to those at the lower lobes of were all near unity in PP, and significantly higher than those in SP (0.98–1.06 vs 0.61–0.94, P < 0.001).ConclusionWe visually and quantitatively observed that PP not only induced more uniform contributions of regional lung ventilation along the ventral-dorsal axis but also minimized the lobar differences of lung functions in comparison with SP. This may help in the clinician’s search for an understanding of the benefits of the application of PP to the patients with ARDS or other gravitationally dependent pathologic lung diseases.Trial registrationRetrospectively registered.