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

<i>Objective.</i>To investigate dynamic shuttle-mode xenon (Xe)-enhanced dual-energy CT (Xe-DECT) imaging for a regional assessment of ventilation in<i>in vivo</i>rabbit lungs.<i>Approach.</i>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 (<i>C</i>_Xe) in the gas phase of the xenon density images. The resultant<i>C</i>_Xeimages 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 (sV˙in min^-1). Ventilation was also qualitatively assessed by evaluating ventilation distributions during washout.<i>Main results.</i>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%,<i>p =</i>0.026. The VDs at baseline did not reveal a reduced ventilation efficiency (sV˙VD:8.4 ± 2.7 min^-1), compared to non-VD areas (sV˙non-VD:7.0 ± 3.1 min^-1),<i>p =</i>0.306. In contrast, MCh-induced VDs were found to have a reduced ventilation efficiency (sV˙VD:4.9 ± 2.3 min^-1), compared to non-VD areas (sV˙non-VD: 6.4 ± 2.3 min^-1),<i>p =</i>0.004<i>. Significance.</i>Dynamic shuttle-mode Xe-DECT during washout enabled regional evaluation of ventilation in healthy and pathological<i>in vivo</i>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.