Tissue Oxygenation Measurement via Spectral Correction
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Solution Overview
Problem
Current methods for measuring tissue oxygen saturation are limited in accuracy and depth penetration, particularly in distinguishing oxygenated and deoxygenated hemoglobin concentrations beneath skin and fat layers, which hampers their effectiveness in diagnosing and monitoring conditions like sepsis and diabetes.
Innovation Solution
A system and method using infrared spectroscopy that calculates tissue oxygen saturation by correcting reflectance spectra for skin and fat contributions, employing a light attenuation equation with terms for absorption and scattering, and a two-stage numerical fitting procedure to derive concentrations of oxygenated and deoxygenated heme, enabling precise determination of oxygen saturation and tension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If infrared reflectance measurements are used to measure tissue oxygen saturation, then non-invasive measurement is achieved, but measurement precision deteriorates due to interference from skin and fat layers
Solution Approach 1:
The patent segments the tissue into multiple layers (skin, fat, muscle) and applies different absorption coefficients to each layer. By dividing the complex tissue structure into manageable segments with distinct optical properties, the system can separately analyze and correct for the contributions of each layer, thereby improving measurement precision while maintaining non-invasive operation.
Solution Approach 2:
The patent introduces a multi-layer optical model as an intermediary between the raw reflectance measurements and the final oxygen saturation calculation. This model acts as a mediator that accounts for the interfering effects of skin and fat layers by computing their expected absorption and scattering, allowing the system to isolate and accurately measure the oxygen saturation signal from deeper muscle tissue.
2Length of stationary object
If infrared radiation is used to probe deep tissues, then penetration depth is improved, but measurement precision deteriorates due to increased scattering and absorption by overlying layers
Solution Approach 1:
The patent divides the optical path into multiple tissue layers, each with its own scattering and absorption characteristics. By segmenting the propagation path, the system can model and correct for the cumulative effects of scattering and absorption in skin and fat layers, enabling accurate measurement of analytes in deeper muscle tissue despite the increased path length.
Solution Approach 2:
The patent changes the wavelength parameters of the infrared radiation to optimize penetration depth while minimizing interference from overlying layers. By selecting specific wavelength ranges where water and fat have reduced absorption, the system achieves deeper penetration with less signal degradation, improving both penetration depth and measurement precision.
3Device complexity
If simple reflectance measurements are performed, then device complexity is reduced, but measurement precision deteriorates due to inability to correct for tissue heterogeneity
Solution Approach 1:
The patent performs preliminary measurements of reflectance at multiple wavelengths before calculating oxygen saturation. By collecting spectral data across a range of wavelengths in advance, the system can subsequently apply multi-component analysis to separate the contributions of different tissue chromophores, achieving high measurement precision without requiring complex real-time processing during the actual measurement.
Solution Approach 2:
The patent adds the wavelength dimension to the simple reflectance measurement by performing spectroscopic analysis across multiple wavelengths. This transforms a single-value reflectance measurement into a spectral profile, enabling the system to distinguish between different tissue components (hemoglobin, water, fat) based on their unique spectral signatures and thereby improve measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for non-invasive, accurate measurement of tissue oxygen saturation and tension, providing sensitive indicators for capillary vasoconstriction and blood volume changes, enabling real-time monitoring and diagnosis of conditions such as hemorrhage, sepsis, and heart disease.
Implementation Method 1
Infrared radiation typically penetrates relatively deeply into tissues, and can be used to probe underneath surface tissues such as skin and fat to measure analytes of interest in deeper muscle and other internal tissues
Implementation Method 2
The light attenuation equation can include a Beer's Law equation that includes terms that correspond to incident light absorption by oxygenated heme, deoxygenated heme, and water in the target tissue
Implementation Method 3
The light attenuation equation can include a series expansion (e.g., a Taylor series expansion) of light attenuation in a plurality of terms that correspond to Beer's Law absorption terms
Implementation Method 4
directing incident radiation to a target tissue and determining reflectance spectra of the target tissue by measuring intensities of reflected radiation from the target tissue at a plurality of radiation wavelengths
Data Source
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AI summary
Methods and systems for calculating tissue oxygenation, e.g., oxygen saturation, in a target tissue are disclosed. In some embodiments, the methods include: (a) directing incident radiation to a target tissue and determining reflectance spectra of the target tissue by measuring intensities of reflected radiation from the target tissue at a plurality of radiation wavelengths; (b) correcting the measured intensities of the reflectance spectra to reduce contributions thereto from skin and fat layers through which the incident radiation propagates; (c) determining oxygen saturation in the target tissue based on the corrected reflectance spectra; and (d) outputting the determined value of oxygen saturation.