Murine pulmonary acinar mechanics during quasi-static inflation using synchrotron refraction-enhanced computed tomography

Abstract

We visualized pulmonary acini in the core regions of the mouse lung in situ using synchrotron refraction-enhanced computed tomography (CT) and evaluated their kinematics during quasi-static inflation. This CT system (with a cube voxel of 2.8 μm) allows excellent visualization of not just the conducting airways, but also the alveolar ducts and sacs, and tracking of the acinar shape and its deformation during inflation. The kinematics of individual alveoli and alveolar clusters with a group of terminal alveoli is influenced not only by the connecting alveolar duct and alveoli, but also by the neighboring structures. Acinar volume was not a linear function of lung volume. The alveolar duct diameter changed dramatically during inflation at low pressures and remained relatively constant above an airway pressure of ∼8 cmH2O during inflation. The ratio of acinar surface area to acinar volume indicates that acinar distension during low-pressure inflation differed from that during inflation over a higher pressure range; in particular, acinar deformation was accordion-like during low-pressure inflation. These results indicated that the alveoli and duct expand differently as total acinar volume increases and that the alveolar duct may expand predominantly during low-pressure inflation. Our findings suggest that acinar deformation in the core regions of the lung is complex and heterogeneous.

Fluid-structure interaction analysis of air flow in pulmonary alveoli during normal breathing in healthy humans

“…In the past few years, there have been a number of successful 3D imaging and reconstructed geometries using micro-Computed Tomography (CT) and radiation-based X-ray Tomographic Microscopy (XTM); these have been used for studies on lung development [15], acinar morphometry [16,17], and acinar mechanics [18,19].…”

Mathematical model of a heterogeneous pulmonary acinus structure

“…number [27]). Therefore, in the current study, we use volumerelated data as the modeling conditions.…”

“…The variety of alveolar and pathway structures in acinus has been widely observed in experiments [1][2][3]27,[38][39][40][41][42]. The average data and their distributions depend on, species [41], inflation level [27,40], region in lungs [23], pathological conditions [42], or ages [28].…”

“…The heterogeneity of the acinus structure on acinar flow remains important in biofluidics [21]. Furthermore, the acinus structure segmented from high-resolution CT images has been analyzed to micrometer resolution [26][27][28], which has the potential to provide quantitative data about the heterogeneity of the acinus structure. Thus, to understand the heterogeneous nature of the acinus structure and its relationship to mechanical phenomena in the lungs, it is vital to develop a parametric heterogeneous acinus structure model and investigate the potential and limitations of the modeling technique.…”

The total number of acini remains constant throughout postnatal rat lung development

“…However, as explained in Barré et al (3) these methods require tedious work, and thus are not suited for studies with larger number of 80 samples. Several publications proposed approaches based on X-ray tomography (10,17,18,20,(34)(35)(36)42). Even if the latter approach would be suitable for the 82 analysis of larger number of sample, to our best knowledge, it has not been done until now, especially not for the analysis of the development of the acini.…”