[POSTECH-SAIT joint research team proposes a fully integrated photoacoustic microscopy (PAM) and photoplethysmography (PPG) system]

[Researchers successfully observe subtle vascular movements following changes in pulse wave morphology]

Wearable devices such as smart watches monitor our health condition around the clock by simply keeping them on the body. These devices measure the wearer’s heart rate based on the pulse signals obtained using light. So far, the changes in the heart rate could only be confirmed numerically but recently, a Korean research team has developed a technology that visualizes vascular movements in real-time.

A POSTECH research team led by Professor Chulhong Kim, Dr. Joongho Ahn, and Dr. Jin Woo Baik (Departments of Electrical Engineering, Convergence IT Engineering, and Mechanical Engineering) has developed an integrated photoacoustic microscopy (PAM) and photoplethysmography (PPG), in collaboration with a research team led by Master (VP of technology) Sung Hyun Nam at Samsung Advanced Institute of Technology (SAIT).

PPG is often used in heart rate measuring sensors in the smart wearable devices. It calculates the heart rate by detecting the changes in optical reflectance following the contraction and relaxation of the heart when LED is irradiated on the skin. This useful technology allows us to check the heart rate in real-time, however, it has limited visual access to the dynamic changes in the body such as vascular movement.

To overcome such limitations, the research team applied PAM to PPG given that the PAM could provide high-resolution imaging of the dynamic changes in the blood vessels over time.

The researchers also confirmed that the new system is able to simultaneously acquire vascular images and changes in the blood volume from human fingers. Furthermore, by directly observing that the change in the pulse wave signal leads to the movement of blood vessels, the team proved that the two changes are linked.

The findings from this study were recently published in the international journal Photoacoustics and are expected to be applicable in various clinical fields such as cardiology and endocrinology.

This study was supported by the Samsung Advanced Institute of Technology (SAIT), National Research Foundation of Korea, Korea Medical Device Development Fund and the Korea Institute for Advancement of Technology (KIAT).

DOI: https://doi.org/10.1016/j.pacs.2022.100374