High-Speed Laser Perfusion Imaging with 2D Integrating Photo Detectors
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Solution Overview
Problem
Current Laser Doppler Imaging (LDI) systems are time-consuming due to mechanical scanning, while fast full-field imaging techniques like Laser Speckle Imaging (LSI) sacrifice spatial resolution, and both struggle to independently measure blood flow parameters like concentration and speed effectively for real-time microcirculation monitoring.
Innovation Solution
A high-speed laser perfusion imaging system combining LDI and LSI using a 2D matrix of integrating photo detectors for real-time, high-resolution imaging, allowing digital photography and speckle contrast analysis with programmable integration of photocurrents to enhance signal-to-noise ratio and process flow-related maps, incorporating a fiberized illumination system for homogeneous illumination and step-scanning for increased measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical scanning is used in LDI systems, then measurement precision is improved, but imaging time increases
Solution Approach 1:
The patent replaces mechanical scanning with a digital/electronic scanning approach using a 2D matrix of photo detectors. The laser beam illuminates the entire field of view simultaneously, and electronic addressing of detector pixels sequentially reads out signals from different spatial locations. This substitution eliminates mechanical moving parts while maintaining the ability to scan and map flow parameters across the tissue surface, thereby reducing imaging time while preserving measurement precision.
Solution Approach 2:
The patent transitions from a 1D scanning approach (single detector moving across the field) to a 2D parallel detection architecture. By arranging photo detectors in a 2D matrix that corresponds to the spatial arrangement of illuminated points on the tissue, the system captures flow information from multiple locations simultaneously. This dimensional expansion enables parallel acquisition of flow maps, dramatically reducing imaging time while maintaining spatial resolution and measurement accuracy.
2Productivity
If full-field illumination is used, then imaging speed is improved, but spatial resolution deteriorates
Solution Approach 1:
The patent segments the illuminated field into multiple discrete spatial locations, each corresponding to a specific pixel in the 2D detector matrix. The laser beam is focused to create distinct illumination spots at different positions on the tissue, and each spot's backscattered light is detected by a corresponding detector element. This segmentation allows simultaneous full-field illumination while maintaining the ability to resolve flow parameters at each individual spatial location, thus preserving spatial resolution while achieving high imaging speed.
Solution Approach 2:
The 2D matrix of photo detectors serves multiple functions simultaneously: it detects backscattered light from the entire illuminated field, spatially resolves signals from different locations through its matrix architecture, and enables parallel measurement of flow parameters across all detected points. This multi-functionality allows the system to achieve both full-field illumination coverage and high spatial resolution without compromise.
3Loss of time
If LSI technique is used, then imaging time is reduced, but ability to independently measure concentration and speed deteriorates
Solution Approach 1:
The patent merges the advantages of LDI (ability to independently measure concentration and speed through Doppler frequency analysis) with the high-speed capability of LSI (full-field illumination and parallel detection). By combining coherent laser illumination with a 2D matrix of fast-readout photo detectors, the system simultaneously achieves rapid imaging and the spectral analysis capability needed to separately determine blood flow concentration and velocity at each pixel location.
Solution Approach 2:
The patent changes the detection parameter from intensity-only measurement (LSI) to frequency-resolved measurement (LDI). By analyzing the Doppler frequency shift in the backscattered light spectrum, the system can independently extract both concentration and velocity information. This parameter change from measuring only intensity variations to measuring spectral characteristics enables independent flow parameter measurement while maintaining high imaging speed through parallel detection.
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 system achieves high-speed, high-resolution imaging of microcirculation with improved accuracy and reduced imaging time, enabling independent measurement of blood flow parameters and enhanced spatial resolution, addressing the limitations of existing LDI and LSI techniques.
Implementation Method 1
The technical principle is based on the Doppler effect wherein the light scattered by moving particles, e.g. blood cells, leads to a slight frequency shift, which can be measured by a heterodyne detector.
Implementation Method 2
In parallel LDI, the signal results from the interference or coherent superposition between a coherent back-scattered light field originating from the coherently illuminated sample of non-moving parts and the coherent back-scattered light field from moving particles contained in the illuminated volume.
Implementation Method 3
Laser Doppler Imaging (LDI) is a non-contact imaging modality based on the coherence properties of light.
Data Source
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AI summary
An instrument for high-speed laser perfusion imaging comprises a laser source, a detector, a signal-processing unit, data memory, and a screen to display the results. A section of the sample surface is illuminated with laser light; the reemitted light from the irradiated surface is collected by the focusing optics on a 2D array of integrating photo detectors. The elements of the 2D array can be accessed individually or in a pre-defined selection of pixels at high speed. This 2D array of random-pixel-access integrating photo detectors (for example an integrating CMOS image senor) is utilized to measure the intensity variations at each individual pixel. The average amplitude and the mean frequency of the measured signal contain information about concentration and speed of moving blood cells. For real-time imaging, the exposure time is used as a parameter to measure relative perfusion changes. These data are stored in a memory and processed with a signal-processing unit. The instrument delivers 2D flow maps of the illuminated sample section. In parallel a conventional image of the sample can be obtained with the same 2D array of photo detectors allowing a simple overlay between a conventional image and processed flow maps. The instrument enables objective high-speed tissue perfusion imaging and real-time perfusion monitoring.