Diffuse Optical Flow Sensors for Pedal Perfusion Assessment
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Solution Overview
Problem
Current methods for assessing blood perfusion in the feet during peripheral vascular interventions are invasive, lack real-time capabilities, and fail to provide reliable, noninvasive measurements of blood flow in various vessel sizes and tissue supplied by these vessels, limiting effective decision-making during procedures.
Innovation Solution
A system utilizing diffuse optical flow sensors positioned on the foot, with an analyzer to determine absolute and relative blood flow rates, and a feedback device providing real-time data to operators, allowing for noninvasive, real-time assessment of blood perfusion across different topographical locations, including pedal angiosomes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If skin perfusion pressure (SPP) is used to measure blood perfusion, then perfusion data can be obtained, but the measurement is unreliable with patients with edema and requires skin temperature normalization to 44°C
Solution Approach 1:
The patent replaces the mechanical SPP measurement system with an optical system using diffuse optical flow sensors. These sensors use light diffusion through tissue to measure blood flow velocity and perfusion, eliminating the need for mechanical pressure cuffs and temperature normalization procedures. The optical method provides reliable measurements in patients with edema because it measures microvascular blood flow directly rather than relying on skin temperature and pressure conditions.
Solution Approach 2:
The patent changes the measurement parameter from skin perfusion pressure (mechanical parameter requiring temperature normalization) to optical blood flow velocity (optical parameter). By measuring the velocity of moving red blood cells through tissue using light diffusion characteristics, the system achieves temperature-independent measurements that work reliably across different patient conditions including edema.
2Measurement precision
If duplex ultrasound (DUX) is used to measure blood flow, then large vessel blood flow can be assessed, but tissue perfusion in the foot cannot be evaluated
Solution Approach 1:
The patent transitions from measuring blood flow in large vessels (one-dimensional lumen flow) to measuring tissue perfusion (three-dimensional microvascular network). The diffuse optical flow sensors detect blood flow in the microcirculation throughout the tissue volume, providing comprehensive tissue perfusion assessment rather than just large vessel flow measurements. This dimensional transition enables evaluation of actual tissue-level perfusion that matters for wound healing.
Solution Approach 2:
The patent replaces the ultrasound-based mechanical measurement system with an optical measurement system. The diffuse optical flow sensors use light diffusion through tissue to detect moving red blood cells in the microcirculation, providing direct tissue perfusion measurement rather than indirect large vessel flow assessment. This optical approach enables comprehensive tissue-level perfusion evaluation.
3Measurement precision
If transcutaneous oxygen monitoring (TCOM) is used to assess tissue perfusion, then oxygen levels can be measured, but real-time data during intervention is not available due to 4-6 week equilibration time
Solution Approach 1:
The patent replaces the chemical/metabolic TCOM measurement system with an optical measurement system. The diffuse optical flow sensors detect blood flow velocity and perfusion in real-time by measuring light diffusion characteristics of moving red blood cells, providing immediate feedback during interventions rather than requiring 4-6 weeks for oxygen equilibration. This enables intraoperative decision-making based on real-time perfusion data.
Solution Approach 2:
The patent measures blood flow velocity and perfusion directly during the intervention procedure rather than waiting for post-procedure equilibration. The real-time optical measurements are obtained immediately before, during, and after the intervention to guide procedural decisions, eliminating the delayed feedback inherent in TCOM methods.
4Measurement precision
If skin perfusion pressure (SPP) measurement is performed, then perfusion data is obtained, but the procedure requires use of a pressure cuff which limits utility as a real-time assessment tool
Solution Approach 1:
The patent replaces the mechanical pressure cuff-based SPP system with a contactless optical measurement system. The diffuse optical flow sensors use light sources and detectors to measure blood flow velocity and perfusion without requiring inflation of pressure cuffs or special positioning equipment. This enables easy, real-time assessment during interventions without interfering with the procedural workflow.
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 immediate, objective, and quantitative assessment of blood perfusion during interventions, guiding procedural decisions and ensuring sufficient perfusion for wound healing, thereby improving limb salvage rates and reducing the risk of premature procedure termination.
Implementation Method 1
a diffuse optical flow (DOF) sensor carried by the support structure
Implementation Method 2
a diffuse optical flow (DOF) sensor carried by the support structure
Data Source
AI summary
Diffuse optical flow (DOF) sensors can be used to assess deep tissue flow. DOF sensors positioned on a foot can provide fluctuating light intensity data to an analyzer, which can then determine absolute and/or relative blood flow. The determined absolute and/or relative blood flow can be signaled to an operator, for example a surgeon for intra-operative use. DOF sensors may be utilized to assess pedal revascularization, for example to guide interventional procedures and to evaluate their efficacy. A support structure can carry a plurality of DOF sensors, such that when the support structure is placed onto a patient's foot, the DOF sensors are disposed adjacent different locations on the foot. The different locations may correspond to different topographical regions of the foot, for example different pedal angiosomes.