Multi-spectral Tissue Imaging with Bandpass Filters
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Solution Overview
Problem
Existing UV-excited fluorescence photography techniques for tissue imaging face limitations such as inability to resolve depth, non-linear signal dependencies, spectral overlap in camera channels, and poor signal-to-noise ratios due to non-uniform illumination and absorption by surrounding chromophores, which compromise the accuracy of analyzing fluorophores like collagen, porphyrin, and porphyrin-related compounds.
Innovation Solution
The use of multi-spectral imaging with selected spectral wavelengths for illumination and detection, based on the excitation-emission spectra of fluorophores and absorption spectra of chromophores, to maximize fluorescence signal capture while suppressing noise from other fluorophores, and normalization for non-uniform illumination and absorption, enabling 2D and 3D chromophore mapping and improved tissue pathology analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If UV-excited fluorescence photography is used for tissue imaging, then fluorescence signals from fluorophores can be captured, but the depth resolution is poor and signal-to-noise ratio is low due to non-uniform illumination and absorption by surrounding chromophores
Solution Approach 1:
The patent segments the broad UV spectrum into multiple narrow spectral bands using bandpass filters. Each spectral band is captured separately at different wavelengths, allowing depth-resolved imaging by analyzing the spectral characteristics of fluorescence signals from different tissue depths. This segmentation approach resolves the contradiction by enabling precise depth measurement while managing system complexity through systematic spectral decomposition.
Solution Approach 2:
The patent adds a spectral dimension to traditional fluorescence imaging by capturing images at multiple wavelengths across the UV spectrum. This transforms 2D spatial imaging into 3D spectral-spatial imaging, where the spectral dimension provides depth information. By analyzing fluorescence intensity variations across different wavelengths, the system achieves depth resolution without requiring complex physical depth-scanning mechanisms.
2Measurement precision
If multiple spectral bands are captured to improve depth resolution, then depth information is obtained, but the device complexity and data processing requirements increase
Solution Approach 1:
The patent employs a single camera system that captures multiple spectral bands by sequentially placing different bandpass filters in the optical path. This multi-functional approach allows one imaging device to perform spectral resolution, depth imaging, and fluorescence detection simultaneously. The system achieves high spectral resolution without requiring multiple specialized detectors, thereby managing device complexity while improving measurement precision.
Solution Approach 2:
The patent uses periodic filter wheel rotation to sequentially present different bandpass filters to the optical path during image capture. This periodic action enables the system to capture multiple spectral bands in a time-multiplexed manner, reducing the need for simultaneous multi-detector systems. The periodic filter switching achieves high spectral resolution while keeping the physical system relatively simple and manageable.
3Measurement precision
If normalization for non-uniform illumination is applied to improve signal-to-noise ratio, then measurement accuracy improves, but processing time and complexity increase
Solution Approach 1:
The patent performs preliminary normalization of fluorescence images by dividing each spectral band image by its corresponding excitation image, which captures the illumination profile. This preliminary action corrects for non-uniform illumination and absorption effects before further analysis. By performing this normalization step early in the processing pipeline, the system improves signal-to-noise ratio and measurement accuracy while minimizing additional processing time through efficient image division operations.
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 enhances the accuracy and depth resolution of tissue imaging by optimizing spectral selection and processing, leading to improved detection and classification of tissue pathologies and skin conditions, and providing effective monitoring of treatment outcomes.
Implementation Method 1
Light-induced fluorescence has been identified as a powerful noninvasive method for tissue pathology recognition and monitoring. In fluorescence imaging, the energy from an external light source is absorbed and almost immediately re-emitted at a longer, lower-energy wavelength.
Implementation Method 2
Fluorescence emission generally depends on the fluorophore's concentration, spatial distribution throughout the tissue, local microenvironment, and light attenuation due to differences in the amount of non-fluorescing chromophores.
Data Source
AI summary
Apparatus and methods are disclosed for multi-spectral imaging of tissue to obtain information about the distribution of fluorophores and chromophores in the tissue. Using specific spectral bands for illumination and specific spectral bands for detection, the signal-to-noise ratio and information related to the distribution of specific fluorophores is enhanced as compared to UV photography, which uses a single RGB image. Furthermore, the chromophore distribution information derived from the multi-spectral absorption images can be used to correct the fluorescence measurements. The combined fluorescence, absorption, and broadband reflectance data can be analyzed for disease diagnosis and skin feature detection.