Remote PPG Tissue Analysis Using Delay-Based Perfusion Mapping
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Solution Overview
Problem
Existing non-contact PPG imaging technologies fail to accurately differentiate and measure perfusion levels in different tissue types within a single image due to averaging of physiological and pathological differences, leading to inadequate assessment of anastomosis healing.
Innovation Solution
A system and method that utilizes PPG amplitude and delay maps to segment tissue regions based on distinct delay characteristics, enabling separate perfusion measurement in different tissue types by deriving PPG perfusion and delay maps from image data, and employing machine learning for classification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If general PPG image analysis is used to measure perfusion in a single image containing different tissue types, then the measurement process is simple, but the measurement precision deteriorates due to averaging of physiological and pathological differences
Solution Approach 1:
The patent segments the image into multiple tissue regions based on distinct PPG delay characteristics. By dividing the image into regions with different delay patterns, the system can measure perfusion separately for each tissue type, avoiding the averaging effect that occurs with general PPG analysis and thereby improving measurement precision.
Solution Approach 2:
The patent applies local quality by using delay map characteristics to identify and separately analyze different tissue types within the image. Each tissue region is treated with specific analysis methods appropriate to its characteristics, allowing accurate perfusion measurement for each local area rather than applying a uniform analysis to the entire image.
2Area of stationary object
If PPG imaging is used to monitor large tissue areas and build perfusion maps, then the coverage area increases, but the ability to differentiate between different tissue types deteriorates due to signal averaging
Solution Approach 1:
The patent segments the large tissue area into distinct regions based on PPG delay characteristics. This segmentation preserves tissue type differentiation information by grouping pixels with similar delay patterns together, allowing the system to maintain both large area coverage and the ability to distinguish between different tissue types.
Solution Approach 2:
The patent uses delay map parameters to differentiate tissue types within the perfusion map. By analyzing temporal delay characteristics in addition to amplitude information, the system can distinguish between different tissue types while monitoring large areas, preventing information loss that would occur with amplitude-only analysis.
3Measurement precision
If separate perfusion measurement for different tissue regions is implemented, then the measurement precision improves, but the device complexity increases due to additional processing requirements
Solution Approach 1:
The patent segments tissue regions based on delay map characteristics, which provides a natural basis for separate perfusion measurement. This segmentation approach improves measurement precision by allowing region-specific analysis while the use of delay maps as segmentation criteria keeps the processing methodology systematic and manageable.
Solution Approach 2:
The patent uses delay maps as a multi-functional tool that serves both as a segmentation basis and as a source of tissue characterization information. This universal approach allows the system to achieve separate perfusion measurement for different tissue regions without requiring entirely separate processing pipelines, thereby limiting the increase in 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 precise perfusion measurement in distinct tissue regions, improving the assessment of anastomosis healing and reducing the risk of post-surgical complications.
Implementation Method 1
PPG imaging utilizes an off-the-shelf camera and a light source to remotely detect the dynamic changes in blood volume beneath the skin
Data Source
Figure 1a~1b
Figure 2~3
Figure 4a~4b
AI summary
A tissue analysis system and method process images to derive a remote PPG perfusion map from PPG amplitude levels obtained from the images as well as a PPG delay map from PPG relative delays between the PPG signals for each image region (pixel) with respect to a reference signal. The images are segmented into one or more tissue regions based on the PPG delay map (or segmentation information identifying tissue regions derived from the PPG delay map are received as input). The different tissue regions have distinct PPG delay characteristics. A level of perfusion can then be determined separately for each tissue region. Thus PPG delay information is used to enable different tissue types to be identified.