Optical Blood Perfusion Monitoring Using PPG Amplitude and Phase
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Solution Overview
Problem
Existing methods for monitoring blood perfusion, such as ankle brachial index tests and laser-based technologies, are either invasive, costly, or lack real-time capability, making it difficult to assess the effectiveness of treatments for peripheral artery disease.
Innovation Solution
A non-invasive system using photoplethysmography (PPG) signals, processed to determine amplitude and phase, to calculate blood perfusion levels through amplitude maps and phase maps, correlating higher amplitudes with higher perfusion and inversely correlating phase distribution with perfusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ankle brachial index test is used to assess perfusion, then diagnosis of PAD can be obtained, but real-time monitoring during procedures is not possible
Solution Approach 1:
The patent replaces the mechanical occlusion-based ABI measurement system with an optical imaging photoplethysmography system. The iPPG system uses light absorption changes in blood to measure perfusion without requiring blood flow blockage, enabling continuous real-time monitoring during procedures like PTA while maintaining perfusion assessment accuracy.
Solution Approach 2:
The patent introduces an optical intermediary (light) to measure perfusion indirectly through blood absorption characteristics. By using light absorption at different wavelengths to detect blood volume changes and flow characteristics, the system achieves real-time perfusion monitoring without mechanical intervention.
2Loss of time
If laser scattering technologies are used for perfusion monitoring, then real-time results can be obtained, but the system becomes costly and complex
Solution Approach 1:
The patent employs inexpensive, commercially available camera sensors and light sources instead of costly laser scattering systems. The iPPG approach uses standard imaging sensors and LED light sources that are already widely available, dramatically reducing system cost and complexity while maintaining real-time monitoring capability.
Solution Approach 2:
The patent uses a simplified optical model that copies the successful principles of laser-based perfusion monitoring but implements them with inexpensive components. By replicating the core measurement principle (optical absorption by blood) using affordable cameras and LEDs rather than expensive lasers, the system achieves the same real-time performance at a fraction of the cost.
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
Provides accurate, real-time monitoring of blood perfusion levels, enabling effective assessment of treatment efficacy during procedures like PTA without the limitations of existing methods.
Implementation Method 1
acquire, from at least one sensor, a plurality of photoplethysmography, PPG, signals indicative of light detected in a region of interest of tissue
Data Source
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AI summary
An apparatus (and method) is for monitoring blood perfusion. A plurality of photoplethysmography, PPG, signals are acquired indicative of light detected in a region of interest of tissue at a plurality of respective locations within the region. The PPG signals are processed to determine an amplitude and preferably also a phase of each of the plurality of PPG signals, and a blood perfusion level is determined at the region of interest based on the amplitudes and preferably also the phases of the PPG signals.