Researchers based in Germany are developing an optoacoustic scanning method to detect the early-warning signs of cardiovascular disease in the tiniest blood vessels under a patient’s skin (Light Sci. Appl., doi:10.1038/s41377-025-02103-6).

In the technique, called fast raster-scan optoacoustic mesoscopy, pulses of 532-nm-wavelength laser light generate ultrasound signals that bounce off blood vessels in the skin. The method produces images of individual capillaries in different layers of skin and reveals that certain medical conditions can affect these capillaries differently.

What small blood vessels reveal

According to medical scientists, small blood vessels react to the onset of hypertension, atherosclerosis and diabetes before these diseases show up in larger arteries and veins. If physicians could measure this problem with capillaries—known as microvascular endothelial dysfunction, or MiVED—they might be able to diagnose life-threatening conditions at an earlier stage. Problems with current imaging methods for capillaries, however, lead clinicians to search for vascular issues by performing ultrasonography on larger blood vessels.

In recent work, a team at Helmholtz Zentrum München and the Technical University of Munich (TUM) improved raster-scan optoacoustic mesoscopy with coaxial ultrasound detectors and dynamic 3D scanning protocols.

The researchers incorporated the mesoscopy into the standard post-occlusive reactive hyperemia (PORH) test, in which a cuff briefly induces ischemia in the patient’s arm. Once the blood flow is restored to the arm, the blood briefly surges through the patient’s tissues (hyperemia) and the vessels may dilate (or not) to accommodate the excess flow. The patients in the study—which included smokers and people with diagnosed cardiovascular disease—simultaneously underwent the mesoscopy, commercial laser Doppler flowmetry and ultrasound study of larger blood vessels.

Testing the tech

During a typical test, slowing the subject’s blood flow with a cuff made the microvessels in the upper layers of skin disappear from view over 7 minutes, while melanin in the skin’s epidermal layer—the imaging reference—remained in constant view. Once the cuff pressure was released, the researchers could see the microvessels surge back into the 4 × 2 mm² view of the mesoscopy device.

The Munich team found differences in the times it took to restore blood-vessel flow between two layers of skin, although not as many structural changes in the capillaries of smokers and cardiovascular-disease patients. The researchers hope their technology illuminates new biomarkers that could lead to better and noninvasive screening for cardiovascular problems.

“By enabling earlier interventions and more precise monitoring, fast-RSOM could transform how cardiovascular diseases are prevented and managed—improving outcomes for patients and reducing health care costs in the long term,” said coauthor Vasilis Ntziachristos.