Germany-based researchers are developing a photoacoustic scanning method to detect 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).

The technology, called fast raster-scanning photoacoustic mesoscopy, uses pulses of laser light at a wavelength of 532 nm to generate ultrasound signals that bounce off blood vessels in the skin. This method produces images of individual capillaries in different layers of the skin, revealing how certain medical conditions can affect these capillaries differently.

What tiny blood vessels reveal

According to medical scientists, the development of high blood pressure, atherosclerosis, and diabetes occur in small blood vessels before they occur in large arteries and veins. If doctors can measure this problem in capillaries, known as microvascular endothelial dysfunction (MiVED), they may be able to diagnose life-threatening conditions at an early stage. However, problems with current methods of imaging capillaries lead clinicians to perform ultrasound examinations on larger vessels to look for vascular problems.

In a recent study, a team from Helmholtz Zentrum München and the Technical University of Munich (TUM) improved raster scanning photoacoustic mesoscopy using a coaxial ultrasound detector and a dynamic 3D scanning protocol.

The researchers incorporated the mesoscope into a standard post-occlusion reactive hyperemia (PORH) test, inducing brief ischemia in the patient’s arm with a cuff. When blood flow is restored to the arm, there may be a temporary surge of blood in the patient’s tissues (hyperemia), and blood vessels may dilate (or not dilate) to accommodate the extra flow. Patients in the study, who included smokers and people diagnosed with cardiovascular disease, underwent simultaneous mesoscopy, commercially available laser Doppler flowmeters, and ultrasound examinations of larger blood vessels.

test the technology

In a typical test, when a cuff was used to slow a subject’s blood flow, microvessels in the upper layers of the skin disappeared from view for seven minutes, while melanin in the epidermal layer of the skin (see image) remained visible at all times. When the cuff pressure was released, the researchers could see the microvessels being pushed back within a 4 × 2 mm area.² Appearance of the mesoscope device.

The Munich research team found that although the structural changes in capillaries in smokers and patients with cardiovascular disease were less significant, there was a difference in the time it took for blood vessels to restore flow between the two layers of skin. The researchers hope their technique will uncover new biomarkers that could lead to better non-invasive screening for cardiovascular disease.

“By enabling earlier intervention and more accurate monitoring, rapid RSOM has the potential to transform the way cardiovascular disease is prevented and managed, improving patient outcomes and reducing healthcare costs in the long term,” said co-author Vasilis Ntziachristos.