Endoscope Processor Oxygen Saturation Spectrum Correction
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Solution Overview
Problem
Existing endoscope systems struggle to accurately measure oxygen saturation levels of blood due to variations in the emission spectrum of illumination light over time or with temperature changes, leading to miscalculations.
Innovation Solution
The endoscope system employs a processor device that adjusts its calculation method for oxygen saturation levels based on spectrum information obtained from the illumination light, using multiple wavelength bands and correlations stored in memory to account for changes in the light spectrum, ensuring accurate measurements even with variable light sources like xenon lamps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a light source whose emission spectrum varies with time (e.g., xenon lamp) is used, then the system can provide broad spectrum coverage, but the difference in absorptance between oxyhemoglobin and deoxyhemoglobin deviates from the specified value with a lapse of time, causing miscalculation of oxygen saturation level
Solution Approach 1:
The system performs preliminary measurement of the actual emission spectrum of the light source using a spectrum sensor before oxygen saturation measurement. This preliminary spectral information is then used to correct the absorption coefficient values, ensuring accurate oxygen saturation calculation despite temporal variations in the light source spectrum.
Solution Approach 2:
The system continuously monitors the emission spectrum of the illumination light using a spectrum sensor and feeds this information back to the control unit. The control unit adjusts the absorption coefficient values based on the measured spectral variations, creating a closed-loop system that maintains measurement accuracy over time.
2Power
If a light source having a phosphor whose emission spectrum varies with temperature variation is used, then the system can achieve efficient light generation, but the difference in absorptance between oxyhemoglobin and deoxyhemoglobin deviates from the specified value due to temperature variation, causing miscalculation
Solution Approach 1:
The system measures the actual emission spectrum of the phosphor-based light source under its current operating temperature conditions before performing oxygen saturation measurement. This preliminary spectral characterization allows the system to compensate for temperature-induced spectral shifts and maintain accurate absorption coefficient values.
Solution Approach 2:
The spectrum sensor continuously monitors variations in the emission spectrum caused by temperature changes in the phosphor light source. This spectral feedback is processed by the control unit to dynamically adjust the absorption coefficient values, compensating for temperature effects and maintaining measurement precision.
3Device complexity
If the difference in absorptance between oxyhemoglobin and deoxyhemoglobin is assumed to be invariable, then the calculation process is simplified, but this assumption leads to miscalculation when the emission spectrum of the light source changes
Solution Approach 1:
The system performs preliminary measurement of the actual emission spectrum using a spectrum sensor before oxygen saturation calculation. This measured spectral information is used to determine accurate absorption coefficient values specific to the current light source conditions, replacing the need for fixed assumed values.
Solution Approach 2:
The system dynamically changes the absorption coefficient parameters based on the measured emission spectrum of the light source. Instead of using fixed assumed values, the absorption coefficients are adjusted according to the actual spectral characteristics, ensuring accurate oxygen saturation calculation under varying light source conditions.
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 precise measurement of oxygen saturation levels despite variations in the emission spectrum, ensuring high accuracy and reliability.
Implementation Method 1
The first illumination light has a first wavelength band in which oxyhemoglobin and deoxyhemoglobin have different absorption coefficients
Implementation Method 2
The oxygen saturation level is calculated using this correlation
Data Source
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AI summary
In imaging an oxygen saturation level of blood, measurement light having a wavelength of 450 to 500 nm, B light, G light, and an R light are sequentially taken out from a xenon lamp (30a). An internal body portion is imaged under irradiation with the measurement, B, G, and R light to obtain image data B1, B2, G2, and R2, respectively. A correlation memory (84) stores first and second correlations (84a, 84b), each being a correlation among the oxygen saturation level and intensity ratios between the image data B1 and G2 and between the image data R2 and G2. When a cumulative lighting time of the xenon lamp (30a) is less than a certain value, the oxygen saturation level is calculated using the first correlation (84a). When the cumulative lighting time equals or exceeds the certain value, the oxygen saturation level is calculated using the second correlation (84b).