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

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). A tissue-based correction was used to isolate the xenon concentration (CXe) in the gas phase of the xenon density images. The resultant CXe 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 (sV ̇ 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 (〖sV ̇〗_VD: 8.4 ± 2.7 min-1), compared to non-VD areas ( 〖sV ̇〗_(non-VD): 7.0 ± 3.1 min-1), p = 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), 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.