Combined vascular-bronchoalveolar casting using formalin-fixed canine lungs and a low viscosity silicone rubber

Anatomic study of the canine bronchial tree using silicone casts, radiography, and CT

This prospective anatomic study examined the canine lower airway lumen morphology by visual inspection, radiography, and CT of silicone casts of two dogs. Study results showed the lobar, bronchopulmonary segmental, and pulmonary lobular organization of the lungs grossly reflected in the hierarchically clustered branching structure of the bronchial tree. Study results also provided a basis for differentiating bronchial and bronchiolar patterns. Whereas images of silicone-filled bronchial lumens produced large-diameter, branching, tapering bands that radiated from the lung hilus, the pattern was different for small airways. Images of silicone-filled bronchiole lumens produced small-diameter, branching, tapering, nonradiating lines that created a speckled pattern resembling micronodules and, unexpectedly during radiography, small-diameter rings with air-filled lumens attributed to positive and negative summation shadows. Consequently, imaging patterns in dogs might be affected by pulmonary lobular morphology and might differentiate large and small airway diseases.

Acute Rat Lung Injury: Feasibility of Assessment with Micro-CT

PURPOSE

To evaluate the feasibility of micro-computed tomography (CT) for analysis of the lung fine structure and its alterations during endotoxin-induced lung injury.

MATERIALS AND METHODS

Intravital perfusion-fixed rat lungs with (n = 5) and without (n = 5) endotoxin perfusion were scanned with micro-CT. Three imaging modalities (conventional histology, intravital microscopy, and electron microscopy) were used to document the effect of endotoxin and the in vivo application of contrast agent (a mixture of barium sulfate, gelatin, and thymol). The effect of endotoxin on structural changes of the lung was evaluated with analysis of variance.

RESULTS

Intravital microscopy, conventional histology, and electron microscopy demonstrated capillary perfusion of contrast agent, inflated alveoli, and no extravasation of barium sulfate in the extravascular space. Systemic application of endotoxin led to a significant increase in the soft-tissue volume of the lungs (ie, tissue edema) (58.09 microm(3)+/- 4.6 [standard error of the mean] vs 8.31 microm(3)+/- 1.63, P <.001) and significant thickening of the alveolar walls (34.01 microm +/- 4.5 vs 14.83 microm +/- 2.5, P <.001) at micro-CT. Simultaneously, endotoxin-treated rat lungs showed a significant reduction in total air space (49.74 microm(3)+/- 1.72 vs 100.99 microm(3)+/- 1.16, P <.001).

CONCLUSION

These findings indicate that micro-CT is feasible for structural evaluation of the lung fine structure and its alterations during endotoxin-induced lung injury.

Feldkamp and circle-and-line cone-beam reconstruction for 3D micro-CT of vascular networks

Detailed morphometric knowledge of the microvascular network is needed for studies relating structure to haemodynamic function in organs like the lung. Clinical volumetric CT is limited to millimetre-order spatial resolution. Since evidence suggests that small arterioles (50 to 300 micrometres) dominate pulmonary haemodynamics, we built a micro-CT scanner, capable of imaging excised lungs in 3D with 100 microm resolution, for basic physiology research. The scanner incorporates a micro-focal (3 microm) x-ray source, an xyz theta stage and a CCD-coupled image intensifier detector. We imaged phantoms and contrast-enhanced rat lungs, reconstructing the data with either the Feldkamp or the circle-and-line cone-beam reconstruction algorithm. We present reconstructions using 180 views over 360 degrees for the circular trajectory, augmented with views from a linear scan for the circle-and-line algorithm. Especially for platelike features perpendicular to the rotation axis and remote from the midplane, the circle-and-line algorithm produces superior reconstructions compared with Feldkamp's algorithm. We conclude that the use of nonplanar source trajectories to perform micro-CT on contrast-enhanced, excised lungs can provide data useful for morphometric analysis of vascular trees, currently down to the 130 microm level.