Integrated DCS Photodiode Circuit for Fast Blood Flow Measurement
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Solution Overview
Problem
Conventional methods for estimating tissue blood flow using Diffuse Correlation Spectroscopy (DCS) require expensive, bulky photon counting detectors and electronics that cannot be integrated into a low-cost probe, limiting bedside monitoring capabilities for diseases such as strokes and vascular disorders.
Innovation Solution
The implementation of integrated diffuse correlation spectroscopy using low-power circuitry and a photodiode with an integrator circuit for direct integration of photon intensities, enabling fast, single-shot measurement of intensity dynamics with reduced noise, and real-time compensation, facilitating low-cost, board-level detection of speckle intensity fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photon counting detectors and electronics are used for DCS measurement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the photon counting function from complex detectors and implements it through a simplified photodiode integrated into an ASIC. The photodiode converts photons to electrical signals, and the ASIC performs correlation analysis, eliminating the need for separate photon counting modules and reducing overall system complexity while maintaining measurement precision.
Solution Approach 2:
The patent uses a photodiode that replicates the light-to-electricity conversion function of photon counting detectors but in a simpler, more integrated form. The ASIC then processes these signals to reconstruct blood flow information, effectively copying the essential measurement capability with reduced complexity.
2Measurement precision
If conventional DCS methods are used, then blood flow measurement accuracy is maintained, but the probe cannot be made low-cost and compact
Solution Approach 1:
The patent merges the photodiode, integrator, and correlation processor into a single integrated ASIC circuit. This consolidation allows the entire DCS measurement system to be embedded in a compact, low-cost probe while maintaining measurement accuracy through the preserved correlation analysis functionality.
Solution Approach 2:
The ASIC acts as an intermediary that processes photodiode signals locally within the probe, eliminating the need for external complex electronics. This intermediary processing enables accurate blood flow measurement while keeping the probe compact and affordable.
3Productivity
If fast sampling of instantaneous intensity fluctuations is performed, then blood flow measurement speed is improved, but noise increases and measurement reliability decreases
Solution Approach 1:
The patent performs preliminary integration of photodiode signals over a defined time period before correlation analysis. This pre-integration step averages out high-frequency noise while preserving the underlying blood flow dynamics, enabling fast measurement without sacrificing reliability.
Solution Approach 2:
The system uses autocorrelation analysis of integrated signals to extract blood flow information while inherently filtering noise. The correlation process provides feedback that distinguishes true physiological signals from random noise, maintaining measurement reliability at high speeds.
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 allows for accurate, fast, and cost-effective measurement of blood flow by integrating signals from a photodiode, reducing measurement noise and enabling real-time compensation, thus improving the signal-to-noise ratio and facilitating bedside monitoring.
Implementation Method 1
a photodiode and an integrator circuit for simple, low-cost, board-level detection of speckle intensity fluctuations
Implementation Method 2
including estimating tissue dynamics from the statistics of integrated photon intensities It(T) sampled at measurement time t, where T is the time of integration. The integrated photon intensities can be given by: It(T) = ∫0T i(t)dt
Data Source
AI summary
Disclosed are various embodiments for integrated diffuse correlation spectroscopy. A first control signal can be sent to a switch to cause an integrator to integrate a current from a photodiode. An integrated current can be received from the integrator, and a data signal can be sent to a computing device based at least in part on the integrated current. A second control signal can be sent to a switch to cause the integrator to cease integrating the current from the photodiode.