NIRS Calibration Device Using Diffuse Reflection
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Solution Overview
Problem
Near-infrared spectroscopy (NIRS) systems face challenges in accurately calibrating and evaluating their functionality due to variations in light source output across devices and over time, affecting the reliability of tissue oxygenation monitoring.
Innovation Solution
A calibration device with a light-absorbing enclosure and a diffuse reflectance member that simulates light attenuation, allowing for the calibration of NIRS systems by adjusting the reflectance member's size and position to achieve consistent light characteristics across wavelengths, and accommodating different optical arrangements and detector distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If discrete light sources are used in NIRS systems, then the system can monitor tissue oxygenation continuously, but the light output varies from device to device and over time due to manufacturability constraints and operating variables such as temperature
Solution Approach 1:
The patent uses a calibration device that creates a known light reflection pattern to copy the expected light characteristics. By comparing actual light measurements against this known pattern, the system can identify and compensate for variations in light source output, thereby maintaining reliability despite manufacturing variations.
Solution Approach 2:
The calibration device allows for adjusting calibration parameters to compensate for light source variations. By changing the calibration parameters based on measured deviations from expected light characteristics, the system maintains accurate tissue oxygenation monitoring despite variations in light source wavelength and intensity.
2Measurement precision
If calibration procedures are implemented to account for light source variations, then measurement accuracy improves, but the calibration process becomes more time-consuming and complex
Solution Approach 1:
The calibration device is designed to be used before clinical measurements to pre-establish calibration parameters. By performing the calibration setup in advance using the known light reflection properties of the calibration device, the system prepares accurate reference values that enable quick subsequent measurements without repeated calibration.
Solution Approach 2:
The calibration device creates a reproducible copy of expected light characteristics through its known reflection properties. This allows the system to quickly compare actual measurements against the known pattern without complex real-time calibration procedures, reducing calibration time while maintaining measurement precision.
3Measurement precision
If multiple wavelengths are used to monitor different hemoglobin states, then the ability to distinguish oxyhemoglobin and deoxyhemoglobin improves, but the complexity of the light source and calibration requirements increase
Solution Approach 1:
The calibration device is designed to work with multiple wavelengths simultaneously using a single known reflection pattern. The same calibration structure serves all wavelength channels, allowing the system to differentiate between oxyhemoglobin and deoxyhemoglobin states without requiring separate calibration procedures for each wavelength, thereby reducing overall device 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
Enables accurate and quick calibration of NIRS systems, ensuring consistent light characteristics and reducing the need for invasive procedures, while being versatile and suitable for disposable use in healthcare environments.
Implementation Method 1
A diffuse reflectance member of a light-reflecting color, e.g., white, is disposed in the enclosure spaced apart from the surface with the windows disposed therein
Implementation Method 2
The inner surface of the wall(s) of the enclosure is of a light-absorbing color; e.g., black
Data Source
AI summary
A method and apparatus for calibrating an NIRS system which includes a sensor portion and for evaluating an NIRS system for proper functioning is provided that includes an enclosure with at least two windows disposed in a wall of the enclosure. The windows allow the light source and one or more detectors of an NIRS system sensor to interface with the enclosure. One window is dedicated to the light source while each light detector has a window dedicated thereto. Thus, the enclosure includes a number of windows equal to the number of light detectors in the NIRS system sensor plus one. The inner surface of the wall(s) of the enclosure is of a light-absorbing color; e.g., black. A diffuse reflectance member of a light-reflecting color, e.g., white, is disposed in the enclosure spaced apart from the surface with the windows disposed therein.