14 February 2007 Optical sensor technology for a noninvasive medical blood diagnosis
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Abstract
NIR-spectroscopy and Photoplethysmography (PPG) and is used for a measurement of blood components. The fact that the absorption-coefficients μa and scattering-coefficients μs for blood differ at difference wavelengths has been exploited and is used for calculation of the optical absorbability characteristics of human blood yielding information on blood components like hemoglobin and oxygen saturation. The measured PPG time signals and the ratio between the peak to peak pulse amplitudes are used for a measurement of these parameters. A newly developed PMD device has been introduced. The non-invasive in-vivo multi-spectral method is based on the radiation of monochromatic light, emitted by laser diodes, through an area of skin on the finger. Deferrals between the proportions of hemoglobin and plasma in the intravasal volume should be detected photo-electrically by signal-analytic evaluation of the signals. The computed nonlinear coefficients are used for the measurement and calculation of the relative hemoglobin concentration change. Results with this photometric method to measure changes in the hemoglobin concentration were demonstrated during measurements with a hemodynamic model and healthy subjects. The PMD is suitable for non-invasive continuous online monitoring of one or more biologic constituent values. The objective of this development is to reduce the dependence on measurement techniques which require that a sample of blood be withdrawn from the patient for in-vitro analysis. Any invasive method used on the patient to obtain blood is accompanied by problems of inconvenience, stress, and discomfort. The patient is also exposed to the normal risks of infection associated with such invasive methods.
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Jens Kraitl, Hartmut Ewald, Hartmut Gehring, "Optical sensor technology for a noninvasive medical blood diagnosis", Proc. SPIE 6445, Optical Diagnostics and Sensing VII, 64450A (14 February 2007); doi: 10.1117/12.702480; https://doi.org/10.1117/12.702480
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