Photoacoustic imaging is a label-free method that forms images by detecting sound waves caused by light being absorbed in tiny blood vessels. This technique can reveal how these vessels change due to various health issues. Although mostly used for research, photoacoustic imaging is now beginning to find application in medical fields like cancer diagnosis and skin conditions. Photoacoustic imaging is highly sensitive to variations in hemodynamics, although difficulties in miniaturizing and optimizing the imaging interface have hampered the development of wearable photoacoustic devices. Now, researchers have developed the first-ever photoacoustic wearable device that is suitable for healthcare applications.

Researchers from the Southern University of Science and Technology (Shenzhen, China) have developed a photoacoustic imaging watch for high-resolution imaging of blood vessels in the skin. The watch could help monitor vital hemodynamic indicators such as heart rate, blood pressure, and how much oxygen is there in the blood, without breaking the skin. To make this typically bulky instrument wearable, the team designed a compact optical resolution photoacoustic microscopy system based on a compact pulsed laser, tight fiber-based light path, and an integrated electronic system fitted in a backpack weighing 7 kilograms. They also created a miniaturized watch-type imaging interface with an adjustable focal plane and a screen display to view the images in real-time.

This system is designed to be used for imaging even when the person wearing it moves around. It features an adaptable laser focus required for imaging multilayered structures such as skin. The photoacoustic imaging system has a lateral resolution of 8.7 µm, which is enough to resolve most microvessels in the skin, It has a maximum field of view of about 3 mm in diameter, which is sufficient for capturing microvascular details. The team tested this device on people to check its focus and its ability to monitor blood flow changes during activities like walking or when blood flow is blocked. The tests confirmed the device is practical for use on the go. The team now aims to make the device even smaller by using a smaller laser and improving its safety and temporal resolution. They are also working on ensuring the stability of the fiber-coupled optical path over extended periods and under more intense conditions such as running and jumping. Additionally, they aim to add features for the quantitative assessment of additional parameters, such as oxygen levels in the blood and blood flow speed, to aid in the early detection of diseases such as cancer and cardiovascular.

“Miniaturized wearable imaging systems like the one we developed could potentially be used by community health centers for preliminary disease diagnosis or for long-term monitoring of parameters related to blood circulation within a hospital setting, offering valuable insights to inform treatments for various diseases,” said research team leader Lei Xi from the Southern University of Science and Technology. 

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