3,624 research outputs found
Automatic Emphysema Detection using Weakly Labeled HRCT Lung Images
A method for automatically quantifying emphysema regions using
High-Resolution Computed Tomography (HRCT) scans of patients with chronic
obstructive pulmonary disease (COPD) that does not require manually annotated
scans for training is presented. HRCT scans of controls and of COPD patients
with diverse disease severity are acquired at two different centers. Textural
features from co-occurrence matrices and Gaussian filter banks are used to
characterize the lung parenchyma in the scans. Two robust versions of multiple
instance learning (MIL) classifiers, miSVM and MILES, are investigated. The
classifiers are trained with the weak labels extracted from the forced
expiratory volume in one minute (FEV) and diffusing capacity of the lungs
for carbon monoxide (DLCO). At test time, the classifiers output a patient
label indicating overall COPD diagnosis and local labels indicating the
presence of emphysema. The classifier performance is compared with manual
annotations by two radiologists, a classical density based method, and
pulmonary function tests (PFTs). The miSVM classifier performed better than
MILES on both patient and emphysema classification. The classifier has a
stronger correlation with PFT than the density based method, the percentage of
emphysema in the intersection of annotations from both radiologists, and the
percentage of emphysema annotated by one of the radiologists. The correlation
between the classifier and the PFT is only outperformed by the second
radiologist. The method is therefore promising for facilitating assessment of
emphysema and reducing inter-observer variability.Comment: Accepted at PLoS ON
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Paired inspiratory-expiratory chest CT scans to assess for small airways disease in COPD
Background: Gas trapping quantified on chest CT scans has been proposed as a surrogate for small airway disease in COPD. We sought to determine if measurements using paired inspiratory and expiratory CT scans may be better able to separate gas trapping due to emphysema from gas trapping due to small airway disease. Methods: Smokers with and without COPD from the COPDGene Study underwent inspiratory and expiratory chest CT scans. Emphysema was quantified by the percent of lung with attenuation < −950HU on inspiratory CT. Four gas trapping measures were defined: (1) Exp−856, the percent of lung < −856HU on expiratory imaging; (2) E/I MLA, the ratio of expiratory to inspiratory mean lung attenuation; (3) RVC856-950, the difference between expiratory and inspiratory lung volumes with attenuation between −856 and −950 HU; and (4) Residuals from the regression of Exp−856 on percent emphysema. Results: In 8517 subjects with complete data, Exp−856 was highly correlated with emphysema. The measures based on paired inspiratory and expiratory CT scans were less strongly correlated with emphysema. Exp−856, E/I MLA and RVC856-950 were predictive of spirometry, exercise capacity and quality of life in all subjects and in subjects without emphysema. In subjects with severe emphysema, E/I MLA and RVC856-950 showed the highest correlations with clinical variables. Conclusions: Quantitative measures based on paired inspiratory and expiratory chest CT scans can be used as markers of small airway disease in smokers with and without COPD, but this will require that future studies acquire both inspiratory and expiratory CT scans
Inter-vendor harmonization of Computed Tomography (CT) reconstruction kernels using unpaired image translation
The reconstruction kernel in computed tomography (CT) generation determines
the texture of the image. Consistency in reconstruction kernels is important as
the underlying CT texture can impact measurements during quantitative image
analysis. Harmonization (i.e., kernel conversion) minimizes differences in
measurements due to inconsistent reconstruction kernels. Existing methods
investigate harmonization of CT scans in single or multiple manufacturers.
However, these methods require paired scans of hard and soft reconstruction
kernels that are spatially and anatomically aligned. Additionally, a large
number of models need to be trained across different kernel pairs within
manufacturers. In this study, we adopt an unpaired image translation approach
to investigate harmonization between and across reconstruction kernels from
different manufacturers by constructing a multipath cycle generative
adversarial network (GAN). We use hard and soft reconstruction kernels from the
Siemens and GE vendors from the National Lung Screening Trial dataset. We use
50 scans from each reconstruction kernel and train a multipath cycle GAN. To
evaluate the effect of harmonization on the reconstruction kernels, we
harmonize 50 scans each from Siemens hard kernel, GE soft kernel and GE hard
kernel to a reference Siemens soft kernel (B30f) and evaluate percent
emphysema. We fit a linear model by considering the age, smoking status, sex
and vendor and perform an analysis of variance (ANOVA) on the emphysema scores.
Our approach minimizes differences in emphysema measurement and highlights the
impact of age, sex, smoking status and vendor on emphysema quantification.Comment: 9 pages, 6 figures, 1 table, Submitted to SPIE Medical Imaging :
Image Processing. San Diego, CA. February 202
Paired inspiratory-expiratory chest CT scans to assess for small airways disease in COPD
Abstract
Background
Gas trapping quantified on chest CT scans has been proposed as a surrogate for small airway disease in COPD. We sought to determine if measurements using paired inspiratory and expiratory CT scans may be better able to separate gas trapping due to emphysema from gas trapping due to small airway disease.
Methods
Smokers with and without COPD from the COPDGene Study underwent inspiratory and expiratory chest CT scans. Emphysema was quantified by the percent of lung with attenuation < −950HU on inspiratory CT. Four gas trapping measures were defined: (1) Exp−856, the percent of lung < −856HU on expiratory imaging; (2) E/I MLA, the ratio of expiratory to inspiratory mean lung attenuation; (3) RVC856-950, the difference between expiratory and inspiratory lung volumes with attenuation between −856 and −950 HU; and (4) Residuals from the regression of Exp−856 on percent emphysema.
Results
In 8517 subjects with complete data, Exp−856 was highly correlated with emphysema. The measures based on paired inspiratory and expiratory CT scans were less strongly correlated with emphysema. Exp−856, E/I MLA and RVC856-950 were predictive of spirometry, exercise capacity and quality of life in all subjects and in subjects without emphysema. In subjects with severe emphysema, E/I MLA and RVC856-950 showed the highest correlations with clinical variables.
Conclusions
Quantitative measures based on paired inspiratory and expiratory chest CT scans can be used as markers of small airway disease in smokers with and without COPD, but this will require that future studies acquire both inspiratory and expiratory CT scans.http://deepblue.lib.umich.edu/bitstream/2027.42/134586/1/12931_2012_Article_1346.pd
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Lung volumes identify an at-risk group in persons with prolonged secondhand tobacco smoke exposure but without overt airflow obstruction.
IntroductionExposure to secondhand smoke (SHS) is associated with occult obstructive lung disease as evident by abnormal airflow indices representing small airway disease despite having preserved spirometry (normal forced expiratory volume in 1 s-to-forced vital capacity ratio, FEV1/FVC). The significance of lung volumes that reflect air trapping in the presence of preserved spirometry is unclear.MethodsTo investigate whether lung volumes representing air trapping could determine susceptibility to respiratory morbidity in people with SHS exposure but without spirometric chronic obstructive pulmonary disease, we examined a cohort of 256 subjects with prolonged occupational SHS exposure and preserved spirometry. We elicited symptom prevalence by structured questionnaires, examined functional capacity (maximum oxygen uptake, VO2max) by exercise testing, and estimated associations of those outcomes with air trapping (plethysmography-measured residual volume-to-total lung capacity ratio, RV/TLC), and progressive air trapping with exertion (increase in fraction of tidal breathing that is flow limited on expiration during exercise (per cent of expiratory flow limitation, %EFL)).ResultsRV/TLC was within the predicted normal limits, but was highly variable spanning 22%±13% and 16%±8% across the increments of FEV1/FVC and FEV1, respectively. Respiratory complaints were prevalent (50.4%) with the most common symptom being ≥2 episodes of cough per year (44.5%). Higher RV/TLC was associated with higher OR of reporting respiratory symptoms (n=256; r2=0.03; p=0.011) and lower VO2max (n=179; r2=0.47; p=0.013), and %EFL was negatively associated with VO2max (n=32; r2=0.40; p=0.017).ConclusionsIn those at risk for obstruction due to SHS exposure but with preserved spirometry, higher RV/TLC identifies a subgroup with increased respiratory symptoms and lower exercise capacity
In Vivo Computed Tomography as a Research Tool to Investigate Asthma and COPD: Where Do We Stand?
Computed tomography (CT) is a clinical tool widely used to assess and followup asthma and chonic obstructive pulmonary disease (COPD) in humans. Strong efforts have been made the last decade to improve this technique as a quantitative research tool. Using semiautomatic softwares, quantification of airway wall thickness, lumen area, and bronchial wall density are available from large to intermediate conductive airways. Skeletonization of the bronchial tree can be built to assess its three-dimensional geometry. Lung parenchyma density can be analysed as a surrogate of small airway disease and emphysema. Since resident cells involve airway wall and lung parenchyma abnormalities, CT provides an accurate and reliable research tool to assess their role in vivo. This litterature review highlights the most recent advances made to assess asthma and COPD with CT, and also their drawbacks and the place of CT in clarifying the complex physiopathology of both diseases
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