NIR Vascular Imaging With Polarization-Based Glare Rejection
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Solution Overview
Problem
The challenge of visually locating near surface vascular structures, such as veins, is exacerbated by limited visible light penetration through tissue, especially in individuals with higher melanin content or obesity, making it difficult to insert hypodermic needles accurately.
Innovation Solution
An imaging system utilizing near-infrared (NIR) light with controlled spectral and polarization properties to enhance visualization of sub-dermal structures by detecting and displaying a vein visualization signal, which is a specific portion of the reflected optical signal, and employing polarization filtering to eliminate specular reflection components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If visible light is used for vein visualization, then the vein can be seen through color absorption (red light absorbed by blood appears dark blue-gray), but the penetration depth is very limited and veins become invisible in people with higher melanin content or obesity
Solution Approach 1:
The patent changes the wavelength parameter of illumination light from visible spectrum to near-infrared spectrum. NIR light at wavelengths around 700-900nm penetrates tissue more deeply than visible light while still being absorbed by hemoglobin, enabling visualization of deeper veins that are invisible to the naked eye or visible light sources.
Solution Approach 2:
The patent converts the harmful effect of melanin absorption (which blocks visible light) into a beneficial situation by using NIR light. Melanin absorption decreases significantly in the NIR range, allowing light to penetrate through pigmented skin and visualize veins that were previously hidden due to high melanin content.
2Loss of information
If red light is used to visualize veins through absorption by blood, then veins appear as dark blue-gray color, but the same red light is absorbed by melanin making visualization harder in people with higher melanin content
Solution Approach 1:
The patent shifts the operating wavelength from the red portion of the visible spectrum (around 600-700nm) to the near-infrared spectrum (700-900nm). This parameter change exploits the fact that hemoglobin maintains strong absorption characteristics in the NIR range while melanin absorption drops significantly, thereby preserving vein contrast information while eliminating melanin interference.
Solution Approach 2:
The patent segments the optical spectrum into different regions and selects the NIR region for vein visualization. By separating the illumination wavelength from the visible range where melanin dominates absorption, the system isolates the hemoglobin absorption signal from the melanin background, achieving selective vein detection.
3Length of stationary object
If NIR light is used to increase penetration depth, then deeper veins become visible, but specular reflection components interfere with the imaging quality
Solution Approach 1:
The patent extracts and removes the harmful specular reflection component from the detected optical signal. By using polarization filtering or spatial filtering techniques, the system separates the desired subsurface scattered light (carrying vein information) from the unwanted surface specular reflection, isolating the useful signal from the interference.
Solution Approach 2:
The patent introduces an intermediary filtering mechanism (polarization filter or spatial filter) between the tissue and the detector. This intermediary selectively transmits the scattered NIR light carrying vein information while blocking the directly reflected specular component, thereby mediating between the deep-penetrating NIR illumination and the image detector.
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 system provides enhanced visualization of veins and other vascular structures below the skin surface, improving accuracy in needle insertion by enhancing image contrast and visibility.
Implementation Method 1
The ability of visible photons to penetrate the tissue is very limited. NIR light is used for illuminating an area of interest and detecting one or more desired optical components of an optical signal reflected back from the imaged area of interest
Implementation Method 2
detecting one or more desired optical components of an optical signal reflected back from the imaged area of interest
Implementation Method 3
NIR light is passed through a first optical system for controlling at least one of spectral and polarization properties of the NIR light
Implementation Method 4
employing polarization filtering to eliminate specular reflection components
Implementation Method 5
The red light encountering the veins is strongly absorbed by the blood and as a result, this location has the appearance of a dark blue-gray color
Implementation Method 6
in people with higher melanin content in their skin, the red component is absorbed by the melanin making visualization of the veins even harder
Data Source
AI summary
The present disclosure relates to a method for visualizing a sub-dermal structure. The method involves illuminating an imaged area of interest (AOI) including sub-dermal regions thereof with near-infrared (NIR) light. The NIR light is passed through a first optical system for controlling at least one of spectral and polarization properties thereof prior to illuminating the imaged AOI. One or more desired optical components of an optical signal reflected back from the imaged area of interest is detected, which represent specific portions of the sub-dermal regions where specific anatomical structure of interest is present. The desired optical components represent a vein visualization signal representing only a portion of the reflected optical signal that falls within a sub-range of intensities, relative to intensities of a remainder of the reflected optical signal. The sub-range of intensities assist in visualizing a vascular structure below a skin layer of a patient. The vein visualization signal may be used to generate a display of the vascular structure on a display system.