Imaging the vasa vasorum. Micro CT and confocal microscopy were used to image the vasa vasorum (A) Mice were anesthetized, heparinized and perfused. A silicone rubber compound, Microfil Blue, was infused through the aortic cannula. Descending aortas with a wide adventitial margin were removed after polymerization was complete, then scanned with a GE eXplore Locus SP microCT scanner at 6.5 micron resolution. Three-dimensional volumetric images were reconstructed from acquired two dimensional projections without averaging, yielding a final voxel size of 6.5 microns (B) Reconstructed images were rotated to obtain luminal images from mice. Descending aorta cross sections probed for smooth muscle actin (green) and lectin (red) were imaged by confocal microscopy (C) adventitia, (D) vessel wall, (E) plaque. To visualize blood vessels in the (F) adventitia, (G) vessel wall and (H) plaque the reconstructed Z-stacks were manually segmented to represent co-localized probes in consecutive axial slices. The obtained contours were modeled and stacked in 3-D for volumetric surface representation.