Quantitative CT detects changes in airway dimensions and air-trapping after bronchial thermoplasty for severe asthma

•QCT can assess post-interventional airways changes in patients with severe asthma after bronchial thermoplasty.•Bronchial thermoplasty reduces airway narrowing and air-trapping.•QCT may be used in therapy guidance and monitoring. Bronchial thermoplasty (BT) can be considered in the treatment of severe asthma to reduce airway smooth muscle mass and bronchoconstriction. We hypothesized that BT may thus have long-term effects on airway dimensions and air-trapping detectable by quantitative computed tomography (QCT). Paired in- and expiratory CT and inspiratory CT were acquired in 17 patients with severe asthma before and up to two years after bronchial thermoplasty and in 11 additional conservatively treated patients with serve asthma, respectively. A fully automatic software calculated the airways metrics for wall thickness (WT), wall percentage (WP), lumen area (LA) and total diameter (TD). Furthermore, lung air-trapping was quantified by determining the quotient of mean lung attenuation in expiration vs. inspiration (E/I MLA) and relative volume change in the Hounsfield interval −950 to −856 in expiration to inspiration (RVC856-950) in a generation- and lobe-based approach, respectively. BT reduced WT for the combined analysis of the 2nd–7th airway generation significantly by 0.06 mm (p = 0.026) and WP by 2.05% (p