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Neue Technik verfolgt Blutzucker mit Licht

von NFI Redaktion

Diabetes is a widespread disease for which unfortunately there is still no cure. Individuals with diabetes must regularly monitor their blood glucose levels and administer insulin to keep it under control. In nearly all cases, blood is taken from the fingertip through a finger prick for blood glucose level measurement. Since this procedure can be painful, researchers worldwide are actively exploring less invasive alternatives that utilize modern electronics.

Several methods have been proposed for measuring blood glucose levels, with the use of infrared light being a prominent example. Devices based on light in the mid-infrared range have shown reasonable performance. However, the required sources, detectors, and optical components are expensive and difficult to integrate into portable devices. Near-infrared light, on the other hand, can be easily generated and detected with cost-effective components. Many smartphones and smartwatches already use NIR sensors to measure heart rate and blood oxygen levels. Unfortunately, glucose in the NIR range does not have clear absorption peaks, making it difficult to differentiate from other blood chemicals like lipids and proteins.

To address this limitation, a research team led by Tomoya Nakazawa of Hamamatsu Photonics (Japan) recently developed a novel method for estimating blood glucose levels from NIR measurements. Their work, which could revolutionize non-invasive blood glucose monitoring, was published in the Journal of Biomedical Optics.

The key contribution of this study is a new blood glucose index derived by the research team from basic NIR formulas. Their approach starts with extracting oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) signals from NIR measurements. By analyzing vast amounts of data on NIR measurements, the researchers recognized that the phase delay (asynchrony) between the low-frequency and oscillating components of HbO2 and Hb signals is closely related to the degree of oxygen consumption during each cardiac cycle and thus serves as a measure of metabolism.

This metabolism index based on phase delays, which other researchers have not reported on, is a scientifically significant discovery.

Tomoya Nakazawa, Hamamatsu Photonics

The team then attempted to demonstrate the relationship between this newly discovered metabolism index and blood glucose levels through a series of experiments. They initially utilized the NIR sensor of a commercial smartwatch by placing it over the finger of a healthy, resting subject. The subject then consumed various sugary and sugar-free beverages to induce changes in blood glucose levels. Similar experiments were conducted using a custom smartphone holder with a bright LED. The results were highly promising, as the changes in the metabolism index closely matched the fluctuations in blood glucose levels measured with a commercial continuous glucose monitoring device. This confirms that the phase delay between HbO2 and Hb is indeed correlated with blood glucose levels.

Clinical trials on individuals with diabetes are still pending to confirm the applicability of the metabolism index in a real-world context. However, the researchers have high hopes for their innovative technique, as Mr. Nakazawa states: „The proposed method can be fundamentally implemented in existing smart devices with pulse oximetry function and is cost-effective, energy-efficient, and straightforward compared to other non-invasive blood glucose monitoring techniques. Therefore, our approach could become a powerful tool for wearable and accessible blood glucose level monitoring devices in the future.“

Let’s hope that these efforts contribute to practical, non-invasive solutions for individuals with diabetes to keep their blood glucose levels in check and minimize the impact of their condition!


SPIE – The International Society for Optics and Photonics

Journal Reference:

Nakazawa, T., et al.. (2024) Non-invasive method for blood glucose estimation based on phase delay between oxy- and deoxyhemoglobin using visible and near-infrared spectroscopy. Journal of Biomedical Optics. doi.org/10.1117/1.jbo.29.3.037001.

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