Abstract
Objectives(a) To assess the effects of computed tomography (CT) scanners, scanning conditions, airway size, and phantom composition on airway dimension measurement and (b) to investigate the limitations of accurate quantitative assessment of small airways using CT images.MethodsAn airway phantom, which was constructed using various types of material and with various tube sizes, was scanned using four CT scanner types under different conditions to calculate airway dimensions, luminal area (Ai), and the wall area percentage (WA%). To investigate the limitations of accurate airway dimension measurement, we then developed a second airway phantom with a thinner tube wall, and compared the clinical CT images of healthy subjects with the phantom images scanned using the same CT scanner. The study using clinical CT images was approved by the local ethics committee, and written informed consent was obtained from all subjects. Data were statistically analyzed using one-way ANOVA.ResultsErrors noted in airway dimension measurement were greater in the tube of small inner radius made of material with a high CT density and on images reconstructed by body algorithm (p<0.001), and there was some variation in error among CT scanners under different fields of view. Airway wall thickness had the maximum effect on the accuracy of measurements with all CT scanners under all scanning conditions, and the magnitude of errors for WA% and Ai varied depending on wall thickness when airways of <1.0-mm wall thickness were measured.ConclusionsThe parameters of airway dimensions measured were affected by airway size, reconstruction algorithm, composition of the airway phantom, and CT scanner types. In dimension measurement of small airways with wall thickness of <1.0 mm, the accuracy of measurement according to quantitative CT parameters can decrease as the walls become thinner.
Highlights
Computed tomography (CT) is considered a useful technique for assessing airway dimensions and it is widely used for noninvasive in vivo structural evaluation of airway remodeling in asthma and chronic obstructive pulmonary disease (COPD) in clinical research
In some reports airway dimension measurements have been performed outside the range validated by their phantoms [6,7,8], and the materials used for constructing airway phantoms have been varied–e.g., tubes made of polyethylene [3], acrylic resin [6], and silicone [7]
Ethics Statement The study using clinical CT images was approved by the ethics committee of Kyoto University, and written informed consent was obtained from all subjects
Summary
Computed tomography (CT) is considered a useful technique for assessing airway dimensions and it is widely used for noninvasive in vivo structural evaluation of airway remodeling in asthma and chronic obstructive pulmonary disease (COPD) in clinical research. In some reports airway dimension measurements have been performed outside the range validated by their phantoms [6,7,8], and the materials used for constructing airway phantoms have been varied–e.g., tubes made of polyethylene [3], acrylic resin [6], and silicone [7]. In these studies, they used different phantom materials, different CT scanners and different scanning conditions: what had effects on errors in airway dimension measurement and what decided the limitations to accurate dimension measurement of small airways are not clear. To date, no report has examined the effects of phantom materials and their CT density on errors in airway dimension measurement using different CT scanners and scanning conditions
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