Ex-vivo micro-CT for the assessment of the structure of paraffin embedded coronary vessels before histology

Purpose: Aim of the study was to demonstrate that absorption-based single low-energy micro-CT can reliably display coronary vessel structure and surrounding tissues after paraffin embedding. Methods and Materials: A micro-CT scanner built by our group was used for the experiments. The x-ray tube was set up in the range of 20-50 kV. A phantom composed of formalin fixed fat and myocardial tissues of rat, dehydrated and paraffin embedded, was used to measure the image contrast of relevant tissues with respect to the background. Similar acquisitions were simulated using standardized attenuation functions and simulated spectra. Real samples of pig excised coronary arteries were also processed in the same way and acquired with similar settings; resulting images were compared to those obtained by histology. The voxel size in the micro-CT images was 21 μm. Results: In phantom, the myocardium contrast vs. paraffin varied from 40% at 20 kV to 29% at 50 kV. The fat contrast was 2% at 20 kV, whereas it was indistinguishable from the background at 50 kV. The pericardium and a balloon induced stenosis were clearly distinguished. A noncalcified fatty streak was also identified. All contrasts in phantom appeared lower than those expected from simulations, probably because of the sample processing. The image quality was sufficient for segmentation purposes, allowing quantitative morphometry within the selected Volume of Interest (VOI). Conclusion: Micro-CT is a useful complementary tool for the assessment of coronary vessels structure after sample embedding in paraffin prior to histological examination. This type of imaging can help for the identification of features for subsequent histological analysis in experimental models of restenosis and atherogenesis