A blood clot in the brain that blocks the supply of oxygen can cause an acute stroke. When a clot occludes a blood vessel, the oxygen supply to the brain is interrupted, and the affected person suffers an acute cerebral stroke. The time span until the vascular blockage is resolved must be as short as possible in order to save as many nerve cells as possible from dying and prevent permanent neurological damage. However, which treatment is best suited for this purpose is not always easy to determine in the required rush. Now, researchers are developing a method based on X-ray analysis and electron microscopy that should enable the optimal therapy to be identified in the shortest possible time.

In a collaborative research that includes investigators from Empa (Switzerland), the researchers are currently developing a diagnostic procedure that can be used to start a tailored therapy for acute stroke patients in a timely manner. Identifying the optimal treatment for acute stroke is difficult because not all blood clots are the same; depending on the type, different types of cells can clump together. Depending on whether red or white blood cells predominate, or on the proportion of fibrin fibers, the thrombus has completely different properties. In addition, thrombi differ greatly in shape. A 15-millimeter-long thrombus that does not completely fill a blood vessel has different mechanical properties than a clot that is only a few millimeters short but completely blocks a vessel and the blood supply to the brain areas behind it. The optimal treatment depends on these differences, whether it is dissolving the clot with drugs or using a so-called stent retriever, a kind of tiny fishing rod with which the thrombus in the blood vessel can be "fished out" and whose material can be selected differently depending on the thrombus.

Radiology currently relies on conventional computed tomography scans to make the therapeutic decision. However, images of the patient's head provide little information about the details of a clot because objects made of similar materials are too difficult to distinguish from one another and to resolve spatially. Moreover, in everyday clinical practice the resolution of the images is limited to 200 micrometers. This is different with laboratory methods, which the researchers used for their new study. The team had examined various blood clots taken from patients during neurosurgical procedures. For this purpose, different laboratory technologies were combined, resulting in virtual 3D images that revealed detailed and previously unknown properties of blood clots. The researchers used 3D micro-tomography to examine individual red blood cells down to the micrometer-range. Such tomography using phase-contrast techniques produces stronger contrast. Objects that are easy to penetrate such as muscles, connective tissue or blood clots can thus, be visualized in particularly fine nuances and in their spatial spread.

Other technologies such as scanning electron microscopy and X-ray diffraction and scattering methods provided additional information down to atomic levels. Here it was shown for the first time that a thrombus not only consists of blood cells and fibrin networks, but can even be interspersed with minerals such as hydroxyapatite, as is known from vessel walls in arterial calcification. However, this detailed information on the peculiarities of a blood clot comes too late, when the thrombus has already been surgically removed. In addition, the newly acquired data cannot be compared with the conventional images and findings in the hospital. Digitalization in medicine, meanwhile, allows the data to be modeled in such a way that an algorithm could read out the detailed information in the future. Eventually, the researchers hope that due to their findings conventional hospital images might be interpreted in a very short time - just as if the blood clot had been examined in an ultrafast virtual laboratory. This would pave the way for a more accurate and personalized therapy for stroke patients in a timely manner. 

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