Abhilash S Kizhakke Puliyakote, Dragoş M Vasilescu, Kriti Sen Sharma, Ge Wang, Eric A Hoffman

We seek to establish a method, using interior tomographic techniques (Xradia MicroXCT-400), for acinar morphometric analysis using the pathway center lines from µCT images as the road-map. Through the application of these techniques, we present a method to extend the atlas of murine lungs to acinar levels, and present a comparison between two age groups of the C57BL/6 strain. Lungs fixed via vascular perfusion were scanned using high-resolution µCT protocols. Individual acini were segmented, and skeletonized paths to alveolar sacs from the entrance to the acinus were formed. Morphometric parameters including branch lengths, diameters, and branching angles were generated. Six mice each, at two age groups (~20, ~90 weeks of age), were studied. Additive Gaussian noise (0 mean and SD 1, 2, 5 and 10) was used to test the robustness of the analytical method. Noise-based variations were within ±6µm for branch lengths and ±5µm for diameters. At a noise level of 10, errors increased. Branch diameters were less susceptible to noise than lengths. There was >95% centerline overlap across all noise levels. The measurements obtained using the centerlines as a road map were not affected by added noise. Acini from younger mice had smaller branch diameters and lengths at all generations without significant differences in branching angles. The relative distribution of volume in the alveolar ducts was similar across both age groups. The method has been demonstrated to be repeatable and robust to image noise and provides a new non-destructive technique to quantitatively assess and compare acinar morphometry.