How accurate is CT morphometry of airway? Phantom and clinical validation study

Abstract

Objective: To assess the reliability of CT airway measurement using phantom and to evaluate its reproducibility using clinical chest CT images.

Materials and methods: The phantom consisted of six tubes with different diameters and wall thicknesses was used. The wall area ratio (%WA) and wall thickness ratio (%WT) were calculated and the difference from the actual value (error ratio) was assessed. In vivo validation was performed with MDCT data of consecutive 10 patients and inter- and intra-rater agreements of the measurement were evaluated.

Results: The error ratio of %WA and %WT increased for the phantom tube with a 1mm or thinner wall thickness. The FOV size has an influence on the airway measurement especially for the tube with 1mm wall thickness. Inter-rater reliabilities between two observers for %WA and %WT were excellent and good intra-class correlation coefficient for %WA and %WT were obtained as 0.825 and 0.811, respectively. Intra-rater reliabilities of measurement also showed good intra-class correlation coefficient for %WA and %WT as 0.822 and 0.800, respectively.

Conclusion: Although the phantom study showed there is a tendency to overestimate the wall area of an airway with a thickness 1mm or less, the software has a potential to be used in assessing longitudinal observation of the same patient, as well as, comparison among different patients due to good intra- and inter-rater reliability.