Fluorescence-Mediated PPG for Quantitative Tissue Perfusion
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Solution Overview
Problem
Existing photoplethysmography (PPG) technologies are unable to provide quantitative assessments of tissue perfusion in standardized units, limiting clinical applications such as wound healing and surgical evaluations.
Innovation Solution
The use of fluorescence-mediated photoplethysmography (FM-PPG) that estimates molar concentration of a fluorescence agent in tissue volume, applying modified Beer-Lambert law to derive blood flow and perfusion measurements in standardized units using fluorescence data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photoplethysmography (PPG) is used to assess blood flow, then the assessment can be performed non-invasively, but the measurement cannot provide quantitative results in standardized units
Solution Approach 1:
The patent introduces fluorescence agents as intermediaries that bind to blood components (hemoglobin, plasma proteins) to enable quantitative measurement. These agents absorb light at specific wavelengths and emit fluorescence signals that are proportional to blood flow and perfusion, allowing conversion of qualitative PPG signals into quantitative measurements in standardized units (mL/min, mL/min/cm²).
Solution Approach 2:
The patent utilizes changes in fluorescence emission parameters (intensity, wavelength, lifetime) in response to varying blood flow conditions. By measuring these parameter changes and applying the modified Beer-Lambert law, the system transforms qualitative optical signals into quantitative blood flow metrics with standardized units.
2Measurement precision
If fluorescence-mediated photoplethysmography (FM-PPG) is implemented to achieve quantitative measurements, then standardized perfusion assessment is enabled, but the device complexity increases
Solution Approach 1:
The patent designs the FM-PPG system to perform multiple functions using a unified approach: it can assess both blood flow and tissue perfusion, work with different fluorescence agents (ICG, fluorescein, rhodamine), and provide quantitative results across various clinical applications (wound healing, surgical assessment, vascular disease) through a single standardized measurement platform.
Solution Approach 2:
The patent replaces complex mechanical blood flow measurement systems (such as Doppler ultrasound or flow meters) with an optical-based fluorescence detection system. This substitution uses light absorption and fluorescence emission principles to infer blood flow and perfusion, simplifying the overall system while enabling quantitative measurements.
3Measurement precision
If fluorescence agents are used to enable quantitative blood flow assessment, then measurement accuracy is improved, but the cost and complexity of the procedure increase
Solution Approach 1:
The patent employs inexpensive, short-lived fluorescence agents that can be administered in small doses and do not require complex delivery systems. These agents (such as ICG, fluorescein, or rhodamine derivatives) are cost-effective, have rapid clearance from the body, and eliminate the need for expensive, long-term implantable devices while still providing accurate quantitative measurements.
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 routine quantification of blood flow and perfusion in tissue, providing consistent and standardized measurements for clinical applications like wound healing and surgical assessments.
Implementation Method 1
receive fluorescence data based on fluorescent light emitted from an excited fluorescence agent in the tissue volume, wherein the fluorescence agent in the tissue volume is excited
Implementation Method 2
applying modified Beer-Lambert law to derive blood flow and perfusion measurements in standardized units using fluorescence data
Data Source
AI summary
Methods and systems for facilitating assessment of blood flow in a tissue volume of a subject are disclosed. In some variations, the method may include: after a predetermined amount of a fluorescence agent has been administered to the subject, exciting the fluorescence agent in the tissue volume such that the excited fluorescence agent emits fluorescent light, acquiring fluorescence data based on the fluorescent light emitted during blood flow through the tissue volume, estimating a molar concentration of the fluorescence agent in the blood flowing through the tissue volume, and generating an assessment of blood flow in the tissue volume based at least in part on the fluorescence data and the estimated molar concentration of the fluorescence agent. The estimated molar concentration may be based on the predetermined amount of the fluorescence agent and an estimated circulating blood volume of the subject.