Wearable fNIRS Probe with Direct LED-Scalp Coupling
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Solution Overview
Problem
Existing functional near-infrared spectroscopy (fNIRS) systems face challenges such as high power losses due to optical couplings, reduced sensitivity, cumbersome patient setups, and limited flexibility in analyzing large tissue regions.
Innovation Solution
A probe device and spectroscopy system are designed with a wearable structure that includes a plurality of housings to house lighting and detection devices. These devices feature a cover structure with an electrode for contacting body tissue, reducing the need for optical fibers and allowing for flexible placement of light sources and detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If optical fibers are used to guide light radiation from light sources to the scalp and collect reflected light, then the system can analyze the entire cerebral cortex, but the system suffers from high power losses due to optical couplings and reduced sensitivity
Solution Approach 1:
The patent removes optical fibers from the system entirely, replacing them with direct LED-to-scalp coupling. The light sources and detectors are positioned in direct contact with the scalp through a wearable cap, eliminating the intermediate optical fiber transmission path that causes power losses through coupling inefficiencies and absorption.
Solution Approach 2:
The patent introduces a wearable cap with integrated light sources and detectors as an intermediary device that enables direct optical coupling with the scalp. This cap serves as the mediator between the measurement system and the brain tissue, allowing for efficient light transmission without requiring optical fibers.
2Area of stationary object
If optical fibers are used for light transmission, then complete brain analysis is possible, but the system becomes cumbersome and heavy for the patient
Solution Approach 1:
The patent extracts and removes the heavy optical fiber components from the system, replacing them with a lightweight wearable cap containing integrated LEDs and detectors. This eliminates the cumbersome nature of fiber-optic cables while maintaining the ability to analyze large brain regions through multiple sensor positions.
Solution Approach 2:
The patent replaces the mechanical fiber-optic transmission system with a direct optical coupling system using LEDs positioned in contact with the scalp. This substitution eliminates the need for flexible fiber bundles and their associated weight and handling complexity.
3Measurement precision
If multiple light sources with different wavelengths are used to determine hemoglobin concentration variations, then accurate tissue analysis is achieved, but optical interference between light sources causes measurement errors
Solution Approach 1:
The patent employs time-multiplexed operation where LEDs emitting different wavelengths are activated in sequential pulses rather than simultaneously. Each wavelength is measured in alternating time slots, eliminating optical interference between different light sources while maintaining the ability to measure both oxygenated and deoxygenated hemoglobin concentrations.
4Reliability
If a fixed arrangement of light sources and detectors is used, then optical coupling is maintained, but flexibility in analyzing different tissue regions is limited
Solution Approach 1:
The patent creates a dynamic system where the wearable cap can be repositioned and reconfigured on the patient's head. Multiple LED and detector positions within the cap allow for flexible targeting of different brain regions while maintaining optical coupling through direct contact. The system adapts to different measurement needs by adjusting which sensors are activated and their spatial arrangement.
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
The solution significantly reduces optical coupling losses, enhances sensitivity, and provides greater flexibility in analyzing brain activity, allowing for deeper tissue analysis with reduced power consumption and improved patient comfort.
Implementation Method 1
uses light sources (for example, laser sources or LEDs) that emit radiation in the near infrared (i.e., with wavelengths comprised between 650 nm and 950 nm), since, for this radiation, the absorption of the light radiation by the body tissue is low. Further, notwithstanding the presence of a significant scattering, the light radiation that impinges upon the body tissue is in any case able to diffuse for several centimeters within the tissue
Implementation Method 2
The light radiation reflected by the body tissue is then detected by at least one detector, which also forms part of the fNIRS system. In particular, the detector generates and sends a signal (for example, a voltage signal), representing the radiation detected, to a processing system.
Implementation Method 3
since the light radiation is principally absorbed by the oxygenated hemoglobin (HbO2) and by the deoxygenated hemoglobin (HHb), which are both present in the blood flow, the processing system is able to determine, by the known Lambert-Beer law, the volume of blood, the variation in time of concentration, and the degree of oxygenation of the hemoglobin in the blood of the tissue analyzed.
Data Source
AI summary
A probe device includes an optical device including at least one of a photodetector or a first light source. A cover structure is included and is arranged in front of the optical device. The cover structure includes an electrode which contacts, in use, a body tissue.