Laser Doppler Flowmetry Frequency Selection for Accurate Perfusion Signals
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Solution Overview
Problem
Existing laser Doppler flowmetry (LDF) systems suffer from accuracy issues due to uncontrollable factors, leading to variations in measurements based on the subject and location on the body, and changes in average blood velocity.
Innovation Solution
A system and method that utilizes a coherent light source, photodetector, and processors to compute power spectral density (PSD) of photodetector output signals, selecting an optimal frequency range based on the amount of physiological information in the signal to enhance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed frequency range is used for LDF measurements, then the measurement process is simple, but the measurement precision varies due to different physiological conditions and locations
Solution Approach 1:
The patent applies dynamics by making the frequency range adaptive rather than fixed. The system dynamically selects the optimal frequency range based on the actual physiological signal characteristics detected in real-time. This is achieved by computing the power spectral density of the photodetector signal and identifying the frequency range that maximizes physiological information content, thereby resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent changes the frequency range parameter based on the detected signal characteristics. Instead of using a predetermined fixed frequency range, the system computes the power spectral density and determines the optimal frequency range that contains the most physiological information. This parameter adaptation directly improves measurement precision while managing complexity through automated analysis.
2Loss of information
If the entire frequency spectrum is analyzed, then all physiological information is captured, but the processing time and computational load increase
Solution Approach 1:
The patent extracts only the relevant physiological information from the photodetector signal by computing the power spectral density and identifying the specific frequency range that contains physiological signals. Instead of processing the entire frequency spectrum, the system extracts and analyzes only the frequencies that contain meaningful physiological data, thereby reducing processing time while preventing information loss.
Solution Approach 2:
The patent applies partial action by analyzing only the portion of the frequency spectrum that contains physiological information rather than the entire spectrum. The system computes the power spectral density and identifies the optimal frequency range, then focuses processing efforts only on this relevant portion, achieving efficient processing without sacrificing physiological information.
3Reliability
If LDF measurements are performed without frequency optimization, then the measurement process is straightforward, but the results vary due to uncontrollable factors such as subject location and blood velocity
Solution Approach 1:
The patent implements feedback by using the computed power spectral density to inform the selection of the optimal frequency range. The system continuously monitors the signal characteristics and adjusts the frequency range selection based on the actual physiological conditions detected. This feedback mechanism ensures consistent and reliable measurements across different subjects and locations by adapting to the specific signal characteristics of each measurement.
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
Improves the accuracy of LDF measurements by determining an optimal frequency range, reducing variability and enhancing the reliability of blood perfusion assessments.
Implementation Method 1
Laser Doppler velocimetry (LDV) is a technique to measure the velocity of a fluid. When LDV is used for measuring blood flow in a body, it is commonly referred to as laser Doppler flowmetry (LDF).
Data Source
AI summary
The invention relates to a system and method for performing a laser Doppler flowmetry, LDF, measurement. The system comprises a coherent light source, a photodetector and one or more processors. The photodetector generates an output signal. The processor(s) determines a selected frequency range for computing an LDF signal. A spectrum of the photodetector output signal is computed for a series of time intervals, thereby obtaining a series of spectra. A measure of the amount of physiological information in the spectra is computed for a number of different frequencies. The selected frequency range is determined as the range of frequencies for which the computed measure of amount of physiological information fulfills a predetermined criterion. The processor(s) compute an LDF signal using the selected frequency range, and output the LDF signal.