Switzerland: Smooth X-ray contrast for research developed

Researchers have developed a new X-ray contrast medium that reaches all blood vessels more reliably and enables precise imaging, helping reduce the number of experimental animals required.

Blood vessels displayed without interruption

Researchers at the University of Zurich have developed a new X-ray contrast medium that is easier to use than previous ones. The contrast medium reaches all blood vessels more reliably and thus enables precise imaging. This helps to reduce the number of experimental animals required.

Various human and animal diseases - such as tumors, strokes, or chronic renal failure - damage the blood vessels. The capillaries, the smallest blood vessels that form fine networks throughout the body are particularly affected. Thanks to their large surface area, they enable the exchange of oxygen between the blood and surrounding tissue, for example in muscles during sports.

Making blood vessels spatially visible

It is important to know precisely the three-dimensional course of the blood vessels for the diagnosis and therapy of cardiovascular and other diseases. In basic science, too, knowledge of the exact anatomy of the capillaries in human and animal organs is crucial for researching diseases that damage blood vessels and testing new therapies. Researchers at the University of Zurich (acronym: UZH), the Swiss National Centre of Competence in Research Kidney Control of Homeostasis (acronym: Kidney.CH)  and the Biomaterials Science Center at the University of Basel have now developed a novel X-ray contrast agent called "XlinCA", which allows the smallest blood vessels to be visualized much more precisely than before using computer tomography technology.

Previous methods often do not work

The contrast agents used so far are added to hardening plastic resins before they are injected into the blood vessels of euthanized animals. However, it is extremely difficult to completely fill the fine capillaries in various organs with the viscous resins. "Without years of experience with the correct injection technique, the capillaries are often not or only partially filled. As a result, up to a quarter of the resulting images are unusable," said Willy Kuo, a post-doctoral researcher at the Physiological Institute of the UZH. Compared to previous contrast agents, "XlinCA" could save up to 25% of the experimental animals, according to Kuo.

The basic problem of conventional methods is that plastic and water cannot be mixed. This always leads to water inclusions in which the contrast medium is missing, which interrupts the spatial representation of the blood vessels on the X-ray image. Water-soluble X-ray contrast media used in medicine do not have this problem. However, they cannot be hardened and leak out through the blood vessel walls into the surrounding tissue within minutes.

A tailor-made contrast medium for optimal results

Contrast media for medical use in humans consist of small molecules and are relatively easy to produce. "A custom-made contrast medium for use in dead organisms was much more difficult to synthesize because it is made of polymers," said Bernhard Spingler, Professor at the Institute of Chemistry at the UZH. "XlinCA" has several advantages compared to previously used X-ray contrast media: It is easy to use and enables the complete and uninterrupted imaging of blood vessels. In addition, several organs or even entire animals such as mice can be examined simultaneously.