Backscatter Oximetry for Stable Tissue Oxygen Measurement
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Solution Overview
Problem
Existing oximetry devices face challenges in maintaining stable contact with the skin, leading to measurement errors when the wearer is moving, due to the need for permanent and stable positioning of light sources and photodetectors relative to the skin, and suboptimal wavelength optimization.
Innovation Solution
A method involving illumination of the skin with incident light at specific wavelengths, simultaneous detection of backscattered radiation at multiple distances, and calibration terms to estimate oxygen content, using a processor to calculate oxygen saturation based on absorption coefficients of oxyhemoglobin and deoxyhemoglobin, and incorporating a bimodal approach for validation and invalidation of measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If permanent and stable contact between optical means and tissue is maintained, then measurement precision is improved, but ease of operation deteriorates due to movement restrictions
Solution Approach 1:
The patent transitions from transmission configuration (light passing through tissue) to backscatter configuration (light reflecting back from tissue surface), changing the spatial dimension of measurement. This allows the device to function with adjacent light sources and photodetectors rather than requiring opposite placement, improving ease of operation while maintaining measurement capability
Solution Approach 2:
The patent optimizes specific parameters including wavelengths (630-680 nm red, 800-1000 nm infrared), backscatter distances (0.5-15 mm), and geometric arrangements to achieve accurate measurements without requiring permanent stable contact, thus resolving the contradiction between measurement precision and ease of operation
2Measurement precision
If light sources and photodetector are placed in transmission configuration, then measurement precision is improved, but device complexity increases due to positioning requirements
Solution Approach 1:
The patent adopts backscatter configuration where light sources and photodetectors are adjacent and face the tissue, eliminating the need for precise opposite positioning required in transmission mode. This reduces device complexity while maintaining measurement precision through optimized backscatter distance and wavelength selection
3Measurement precision
If multiple wavelengths are used for optimization, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the spectral range into two distinct segments: red light (630-680 nm) and infrared light (800-1000 nm). This segmentation allows targeted optimization for hemoglobin absorption characteristics while managing device complexity through focused wavelength selection rather than continuous spectral coverage
Solution Approach 2:
The patent optimizes specific wavelength parameters within the red and infrared ranges to match hemoglobin absorption peaks, achieving high measurement precision through parameter optimization rather than using all possible wavelengths, thus balancing precision and complexity
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 method provides robust and accurate estimation of oxygen content in living tissue, reducing measurement errors caused by movement and improving wavelength optimization, ensuring reliable oximetry readings even when the device is not perfectly stationary.
Implementation Method 1
illumination of a surface of the fabric by an incident light beam, at a wavelength of interest... absorption coefficients of oxyhemoglobin and deoxyhemoglobin
Implementation Method 2
simultaneous detection of backscattered radiation emanating from the surface of the sample... comparison of the intensities of the detected backscattered radiation
Data Source
Figure 1A~1C
Figure 2A~3
Figure 4A~4G
AI summary
The invention is a method for determining the oxygen content of living body tissue by an optical method, using a backscattering configuration. The tissue being examined is illuminated by an incident beam, defining an elementary illumination zone. Backscattered radiation is detected, this radiation emanating from the surface of the sample outside the elementary scattering zone, and at a distance, called the backscattering distance, from it. The method can be bimodal, in which case the oxygen content is determined according to a first modality. When the first modality is deemed unreliable, or potentially unreliable, a second modality is implemented. The first modality is based on determining the temporal evolution of reflectance along two wavelengths, while the second modality is based on the spatial evolution of reflectance along one wavelength.