Regional ventilation imaging in normal and bronchoconstricted in vivo rabbit lungs using dynamic shuttle mode Xe-enhanced DECT imaging

Abstract Objective. To investigate dynamic shuttle-mode xenon (Xe)-enhanced dual-energy CT (Xe-DECT) imaging for a regional assessment of ventilation in in vivo rabbit lungs. Approach. Four mechanically ventilated rabbits were scanned during the washout of a 70% xenon in 30% oxygen gas mixture using dynamic shuttle-mode DECT at baseline and during methacholine (MCh)-induced bronchoconstriction (post-MCh). Material decomposition was applied to generate xenon and tissue density images (mg ml −1 ). A tissue-based correction was used to isolate the xenon concentration ( C Xe ) in the gas phase of the xenon density images. The resultant C Xe images were used to investigate regional ventilation defects (VDs) by comparing the VD fraction (VDF, expressed as percentage) between baseline and post-MCh conditions. Additionally, regional ventilation efficiency within the VDs and surrounding (non-VD) areas was quantified as specific ventilation ( s V ˙ in min −1 ). Ventilation was also qualitatively assessed by evaluating ventilation distributions during washout. Main results. MCh-induced bronchoconstriction resulted in an increase in VDF. The average VDF at baseline was 13.8 ± 8.5%, compared to an average post-MCh VDF of 29.6 ± 7.7%, p = 0.026. The VDs at baseline did not reveal a reduced ventilation efficiency ( s V ˙ V D : 8.4 ± 2.7 min −1 ), compared to non-VD areas ( s V ˙ n o n − V D : 7.0 ± 3.1 min −1 ), p = 0.306. In contrast, MCh-induced VDs were found to have a reduced ventilation efficiency ( s V ˙ V D : 4.9 ± 2.3 min −1 ), compared to non-VD areas ( s V ˙ n o n − V D : 6.4 ± 2.3 min −1 ), p = 0.004 . Significance. Dynamic shuttle-mode Xe-DECT during washout enabled regional evaluation of ventilation in healthy and pathological in vivo rabbit lungs. As traditional lung function tests offer only global assessments of respiratory impairment, there is a growing interest in pulmonary functional imaging to enable quantitative evaluation of regional lung function.