Near-infrared Spectroscopy (NIRS)
For a clinician, it is important to understand the basic principles of NIRS, to know the limits of use and to interpret them correctly. NIRS is a technique in which the amount of absorption by which chromium molecules [oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb), cytochrome-c oxidase (CCO), myoglobin)] is measured as NIR light passes through the tissues. Chromophore can also absorb NIR light in tissues. There are molecules called. These molecules have specific absorption rates which vary according to the oxygen concentration in the tissue. The amount of light absorbed by the tissues is directly dependent on the chromophore concentration. At least two different wavelengths for comparison of chromophore concentration in NIRS measurements should be used. These two wavelengths are commonly used in measurements as O2Hb and HHb used in the measurements show the greatest difference in absorption at light of 700 to 850 nm wavelength. While two wavelengths are used in the first produced devices, the accuracy rate of the measurements is increased by using multiple wavelengths in the devices used today. The basis of the NIRS working principle is the Beer-Lambert law, an optical physics law. According to this law, the light is absorbed according to the material it passes through. Spectral resolution spectroscopy, frequency have developed techniques for dependent spectroscopy and time-dependent spectroscopy. Determining the chromophore concentration level in benign and malignant nodules in thyroid nodules has become simpler with these methods. I am hopeful that a non-invasive diagnostic method will be developed by the departments that support this hypothesis without being done in the future.
The infrared absorption spectroscopy is a fully developed technique in molecules analysis and you really got the point of the Beer-Lambert based technique. I'm not sure on your applications condition， what kind of non-invasive diagnostic method? Can you provide an example to explain your clinical need? So it would be helpful for others to carry on the discussion.
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