Researchers present a compact device that combines diffuse correlation spectroscopy (DCS) and time-domain near-infrared spectroscopy (NIRS). It allows direct measurements of the blood flow, tissue oxygenation, and oxygen metabolism rate.
A pattern of bright spots
Diffuse optics has become a very useful technology in the biomedical research field in recent years, especially in clinical applications such as brain monitoring or tumor characterization.
Diffuse correlation spectroscopy is a technique that allows researchers and clinicians to measure the blood flow in the microvessels non-invasively. Laser light in the near-infrared region penetrates inside the human tissue, up to a few cm in-depth, where the red blood cells flow in the vessels. The light scatters the photons, creating a pattern of bright and dark spots at the detection plane, seen with variable intensities depending on the cell movement. By measuring the intensity fluctuation of a single region over time, researchers can quantify the blood flow variation. This technique has allowed clinicians, for instance, to continuously monitor the blood flow of comatose patients or patients undergoing clinical interventions.
A compact, multi-distance, and hybrid device
In an article published in the journal Sensors, researchers from the Politecnico di Milano and the Italian National research council, part of Vascovid, present a new hybrid device to measure blood flow, tissue oxygenation, and oxygen metabolism rate.
The team integrated the diffuse correlation spectroscopy (DCS)module with a compact advanced time-domain near-infrared spectroscopy (NIRS). This technology is a spectroscopic method, widely used in medical and physiological diagnostics, to indirectly measure oxygenation in human tissues. It measures the light absorbance in the tissues to calculate the oxy-hemoglobin (oxy-HB) and deoxy-hemoglobin (deoxy-HB).
Combining the current DCS technology with time-domain NIRS allows researchers to perform both measurements at the same time
By combining the current DCS technology with time-domain NIRS, researchers can perform both measurements at the same time and obtain certain information that the two techniques do not provide separately, as the rate of oxygen consumption in the tissue.
Researchers tested the device’s performance, in terms of stability and replicability, its sensitivity to deep tissues, and its ability to measure the flow variations. They obtained both high stability for long measurements and strong reproducibility for different days. They also highlighted the importance of the multi-distance device to discriminate the effect of superficial layers.
Finally, the team also observed how the signals of both technologies interacted. They conducted in vivo experiments to test the device’s capacity to measure the blood flow when occluding the veins and arteries of two volunteers’ arms.
Read the article
Amendola, C.; Lacerenza, M.; Buttafava, M.; Tosi, A.; Spinelli, L.; Contini, D.; Torricelli, A. A Compact Multi-Distance DCS and Time Domain NIRS Hybrid System for Hemodynamic and Metabolic Measurements. Sensors 2021, 21, 870. https://doi.org/10.3390/s21030870
