title: Optimized murine lung preparation for detailed structural evaluation via micro-computed tomography.
abstract: Utilizing micro-X-ray CT (μCT) imaging, we sought to generate an atlas of in vivo and intact/ex vivo lungs from normal murine strains. In vivo imaging allows visualization of parenchymal density and small airways (15-28 μm/voxel). Ex vivo imaging of the intact lung via μCT allows for improved understanding of the three-dimensional lung architecture at the alveolar level with voxel dimensions of 1-2 μm. μCT requires that air spaces remain air-filled to detect alveolar architecture while in vivo structural geometry of the lungs is maintained. To achieve these requirements, a fixation and imaging methodology that permits nondestructive whole lung ex vivo μCT imaging has been implemented and tested. After in vivo imaging, lungs from supine anesthetized C57Bl/6 mice, at 15, 20, and 25 cmH(2)O airway pressure, were fixed in situ via vascular perfusion using a two-stage flushing system while held at 20 cmH(2)O airway pressure. Extracted fixed lungs were air-dried. Whole lung volume was acquired at 1, 7, 21, and >70 days after the lungs were dried and served as validation for fixation stability. No significant shrinkage was observed: +8.95% change from in vivo to fixed lung (P = 0.12), -1.47% change from day 1 to day 7 (P = 0.07), -2.51% change from day 1 to day 21 (P = 0.05), and -4.90% change from day 1 to day 70 and thereafter (P = 0.04). μCT evaluation showed well-fixed alveoli and capillary beds correlating with histological analysis. A fixation and imaging method has been established for μCT imaging of the murine lung that allows for ex vivo morphometric analysis, representative of the in vivo lung.
authors.affiliation: Department of Radiology, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: Dragos M
authors.initials: DM
authors.lastname: Vasilescu
authors.forename: Lars
authors.initials: L
authors.lastname: Knudsen
authors.forename: Matthias
authors.initials: M
authors.lastname: Ochs
authors.forename: Ewald R
authors.initials: ER
authors.lastname: Weibel
authors.forename: Eric A
authors.initials: EA
authors.lastname: Hoffman
mesh_terms: D000818:Animals; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods*; D008168:Lung / Q000000981:diagnostic imaging* / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010477:Perfusion / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*