Automated method of bronchus and artery dimension measurement in an adult bronchiectasis population

Bronchiectasis (BE) is a disease defined by irreversible dilatation of the airway. Computed tomography (CT) plays an important role in the detection and quantification of BE. The aim of this study was three-fold: 1) to assess bronchus-artery (BA) dimensions using fully automated software in a cohort of BE disease patients; 2) to compare BA dimensions with semi-quantitative BEST-CT (Bronchiectasis Scoring Technique for CT) scores for BE and bronchial wall thickening; and 3) to explore the structure-function relationship between BA-method lumen dimensions and spirometry outcomes.

Baseline CTs of BE patients who participated in a clinical trial were collected retrospectively. CTs were analysed manually with the BEST-CT scoring system and automatically using LungQ (v.2.1.0.1, Thirona, The Netherlands), which measures the following BA dimensions: diameters of bronchial outer wall (B_out), bronchial inner wall (B_in) and artery (A), and bronchial wall thickness (B_wt) and computes BA ratios (B_out/A and B_in/A) to assess bronchial widening. To assess bronchial wall thickness, we used the B_wt/A ratio and the ratio between the bronchus wall area (B_wa) and the area defined by the outer airway (B_oa) (B_wa/B_oa).

In total, 65 patients and 16 900 BA pairs were analysed by the automated BA method. The median (range) percentage of BA pairs defined as widened was 69 (55-84)% per CT using a cut-off value of 1.5 for B_out/A, and 53 (42-65)% of bronchial wall were thickened using a cut-off value of 0.14 for B_wt/A. BA dimensions were correlated with comparable outcomes for the BEST-CT scoring method with a correlation coefficient varying between 0.21 to 0.51. The major CT BA determinants of airflow obstruction were bronchial wall thickness (p=0.001) and a narrower bronchial inner diameter (p=0.003).

The automated BA method, which is an accurate and sensitive tool, demonstrates a stronger correlation between visual and automated assessment and lung function when using a higher cut-off value to define bronchiectasis.