(C-101) Comparison of contrast agents for the visualization of tissue vasculature using ex vivo micro-CT imaging

Introduction:: To fully understand angiogenesis and its role in cancer progression, visualization of the microvascular network is crucial for cancer diagnosis, predicting metastatic growth, and evaluating therapeutic protocols. The use of microscale computed tomography (micro-CT) and ex vivo contrast agents provides high-resolution images of tissue microvasculature in volumetric space. The purpose of this research was to compare a selection of commercially available contrast agents to determine an optimal solution for tumor microvascular visualization.


Materials and Methods:: A population of 16 female nude athymic mice (Charles River Laboratories) were implanted with MDA-MB-231 breast cancer cells (ATCC) orthotopically in the lower mammary pad. Animals were evenly divided into four groups, namely, control (no contrast agent), barium sulfate (BaSO₄), Vascupaint, and Microfil. Animals were anesthetized prior to transcarotid microsurgery to inject 2 mL of the specific contrast agent for intravascular distribution throughout the animal. After a small incision in the midline was performed to expose and isolate the carotid artery, a small arteriotomy was made and the tip of a PE10-polythlene tube was inserted and secured using sutures. A syringe was attached to the other end of the tubing and the contrast agent was slowly perfused using an infusion pump. Following successful perfusion (made via visual confirmation), animals and extracted organs underwent full body and high-resolution contrast-enhanced micro-CT scanning (IO/CT, MILabs). Images were reconstructed and analyzed using image analysis software to extract mean intensity signals.

Results, Conclusions, and Discussions:: Preliminary ex vivo results reveal that Vascupaint and BaSO₄ are useful for microvascular visualization. Both contrast agents showed superior contrast-enhanced micro-CT image enhancement in the brain and kidney as compared to Microfil (p < 0.05). For the various contrast agents, there were no differences in image enhancement from the liver, spleen, or tumor tissue (p > 0.21). Moreover, use of Vascupaint and BaSO₄ allowed for visualization of smaller microvascular structures on a scale of 20 µm, which were considered smaller compared to measurements from contrast-enhanced micro-CT images using Microfil (p < 0.004). Overall, our study suggests that use of Vascupaint or BaSO₄ is more than sufficient for ex vivo visualization of microvascular structures using contrast-enhanced micro-CT imaging as these contrast agents more effectively perfused smaller blood vessels.

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