Radiopaque dyes allow vessel imaging in lung tissue using laboratory phase contrast micro-CT

Phase contrast micro-CT is a powerful technique allowing imaging of soft tissue at synchrotrons or using lab- oratory sources. The use of contrast agents is a useful approach when imaging vascular structures. However, common x-ray contrast agents typically rely on heavy metals to increase absorption, which may affect the phase contrast and cause artifacts in the reconstructed volumes. Thus, utilizing an agent with lower attenuation similar to soft tissue is clearly advantageous. Here, we evaluated different colored radiopaque solutions (tissue marking dyes) which had been injected into the vascular system of bovine lung samples, prior to embedding in paraffin. Scans were performed using a micro-focus x-tube calibrated to 10 µm spot size at 70 kV and a photon counting detector with a silicon sensor and 75 µm pixels. The resulting volumes have a voxel size of (25 µm)3, limited by the size of the samples, but sufficient to resolve the vascular system. Experiments confirmed that sufficient perfusion of the vessels with the dyes could be achieved, and the different dyes could be clearly discerned in the reconstructed volumes without causing artifacts allowing to clearly identify features in the soft tissue. Further, the findings were confirmed by histology.Keywords