Non-invasive Optical Detection in Scattering Media
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical detection systems face challenges in achieving high spatial resolution and temporal sensitivity for detecting fast-optical signals in brain tissue due to the diffusive nature of light propagation through tissues like the skull, leading to limited penetration depth and sensitivity to background noise.
Innovation Solution
A non-invasive optical detection system utilizing an interferometer that generates interference light patterns by combining sample light with reference light, allowing for the detection of spatial components and physiological events through arrays of detectors, with a processor analyzing intensity distributions to identify and quantify fast-optical signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical detection systems use diffusive optical imaging techniques with moderate amounts of near-infrared or visible light radiation, then the measurement is safe and gentle for biological subjects, but the spatial resolution is limited to centimeters and penetration depth is limited to a few millimeters
Solution Approach 1:
The system uses pulsed light sources instead of continuous illumination, dynamically modulating the light in time-domain to encode depth information. This allows differentiation of photons based on their flight time, enabling depth resolution despite diffusive scattering, while maintaining safety through controlled pulse durations and repetition rates
Solution Approach 2:
The system changes the temporal parameter of light delivery by using picosecond-pulse durations with repetition rates between 1 MHz and 1 GHz. This parameter transformation converts the diffusive optical measurement into a time-resolved measurement, where the temporal distribution of detected photons carries spatial information about the scattering medium, achieving centimeter-scale depth resolution while maintaining safety
2Measurement precision
If conventional optical detection systems attempt to increase spatial resolution by locating multiple optical sources and detectors along the surface of the head, then more measurement points are obtained, but the device complexity increases and the fundamental diffusive nature of light propagation still limits resolution
Solution Approach 1:
The system adds a temporal dimension to the optical measurement by resolving photon arrival times with picosecond precision. This time-of-flight dimension provides depth information without requiring multiple spatially distributed detectors, as each detector can resolve photons from different depths based on their flight time, effectively converting a 2D spatial measurement problem into a 3D measurement including time
3Ease of operation
If conventional optical detection systems use diffusive light propagation through highly scattering media like brain tissue, then non-invasive measurement is achieved, but the light paths become random walks making spatial resolution impossible without detailed microscopic knowledge of scattering characteristics
Solution Approach 1:
The system uses time-correlated single photon counting with histogramming to build up statistical distributions of photon flight times. This feedback mechanism accumulates information from many individual photon detections to reconstruct the temporal point spread function, which encodes spatial information about the scattering medium without requiring prior knowledge of its microscopic structure
4Speed
If conventional optical detection systems measure fast changes in optical scattering inside tissue, then neural activity can be detected, but the diffusive nature of light propagation creates challenges since essentially all paths between source and detector are highly scattered
Solution Approach 1:
The system uses picosecond-pulse precursors that are significantly shorter than the expected photon flight time through tissue. This preliminary action creates a temporal window where early-arriving photons can be detected before the bulk of scattered photons arrive, allowing detection of fast optical signals associated with neural activity before diffusive scattering completely randomizes the temporal distribution
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
The system enhances temporal sensitivity and spatial resolution, enabling the detection of fast-optical signals with improved signal-to-noise ratio, allowing for real-time monitoring of neural activity without the need for multiple measurements.
Implementation Method 1
The interferometer is further configured for combining reference light with the sample light pattern to generate at least one interference light pattern (e.g., a speckle light pattern)
Implementation Method 2
the sample light is scattered by the target volume of interest, resulting in a sample light pattern that exits the anatomical structure
Data Source
AI summary
A non-invasive optical detection system and method are provided. Sample light is delivered into a target volume of interest, whereby the sample light is scattered by the target volume of interest, resulting in a sample light pattern that exits the anatomical structure. Reference light is combined with the sample light pattern to generate at least one interference light pattern, each of which may have a time varying interference component that integrates to a first value in the absence of the physiological event, and that integrates to a second greater value in the presence of the physiological event. Intensities of spatial components of each interference light pattern are detected during a measurement period. A function of the detected spatial component intensities of the interference light pattern(s) is analyzed, and a presence of the physiological event in the target volume of interest is determined based on the analysis.