Diffuse Optical Tomography System With Isolated Optode Arrays
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Solution Overview
Problem
Existing diffuse optical imaging systems face challenges with limited lateral resolution and no depth-sectioning capabilities due to the use of sparse optode arrays, which also result in high crosstalk and dynamic range issues, especially in high-density optode grids, limiting their ability to accurately measure and reconstruct brain activity signals.
Innovation Solution
A high-density diffuse optical tomography system with discrete isolated sources and detectors, utilizing digital multiplexing and isolated power supplies to minimize crosstalk, combined with flexible time and frequency encoding strategies determined by software, allowing for high dynamic range and low crosstalk, enabling improved lateral resolution and depth profiling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sparse optode arrays are used, then device complexity is reduced, but measurement precision and lateral resolution deteriorate
Solution Approach 1:
The optode array is segmented into multiple independent groups (e.g., 3x3 or 4x4 grid patterns) where each group functions as an independent measurement unit. This segmentation allows the system to achieve high measurement precision through multiple discrete measurement points while keeping each individual optode simple and the overall system manageable in complexity.
2Measurement precision
If high-density optode grids are used, then lateral resolution is improved, but crosstalk and dynamic range issues worsen
Solution Approach 1:
The system employs time-division multiplexing where optodes are activated in periodic sequences rather than simultaneously. Each optode group is activated at specific time intervals, allowing the detection system to distinguish signals from different optodes temporally. This periodic activation eliminates optical crosstalk between adjacent high-density optodes while maintaining high lateral resolution through the dense spatial arrangement.
3Measurement precision
If high-density optode grids are used, then lateral resolution is improved, but device complexity worsens
Solution Approach 1:
Time-division multiplexing with periodic optode activation reduces the simultaneous channel count requirement. Instead of requiring all high-density optodes to operate simultaneously, the system cycles through optode groups sequentially, reducing the instantaneous bandwidth and channel count requirements while maintaining the benefits of high spatial resolution through the dense optode configuration.
Solution Approach 2:
The high-density optode grid is segmented into multiple independent groups that can be controlled and read out separately. This segmentation allows the complex high-density array to be managed through modular control circuits, where each group has its own dedicated control and detection pathways, thereby reducing the overall system complexity despite the high spatial resolution achieved.
4Device complexity
If nearest neighbor optode pairs only are used, then device complexity is reduced, but measurement precision and depth-sectioning capabilities deteriorate
Solution Approach 1:
The measurement configuration is segmented into multiple distance categories (nearest neighbor, second nearest neighbor, and intermediate distances). By systematically incorporating optode pairs at various separation distances rather than only nearest neighbors, the system achieves depth-sectioning capabilities through multi-distance measurements while maintaining organized, modular control that manages system complexity.
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 achieves high-speed imaging with a dynamic range of at least 107 and crosstalk rejection of less than 10^-6, enabling accurate volumetric localization and reconstruction of brain activity signals with improved activation-to-background ratios and reduced noise.
Implementation Method 1
The light is then received by the detectors 120 and preprocessed in the gain stages 122
Implementation Method 2
The light is then received by the detectors 120 and preprocessed in the gain stages 122
Data Source
AI summary
A high performance imaging system for diffuse optical tomography is disclosed. A dense grid utilizing sources, e.g., light emitting diodes (“LEDs”), that achieve high performance at high speed with a high dynamic range and low inter-channel crosstalk are complemented by a system of discrete, isolated receivers, e.g., avalanche photodiodes (“APDs”). The source channels have dedicated reconfigurable encoding control signals, and the detector channels have reconfigurable decoding, allowing maximum flexibility and optimal mixtures of frequency and time encoding and decoding. Each detector channel is analyzed by dedicated, isolated, high-bandwidth receiver circuitry so that no channel gain switching is necessary. The resulting improvements to DOT system performance, e.g., increased dynamic range and decreased crosstalk, enable higher density imaging arrays and provide significantly enhanced DOT image quality. A processor can be utilized to provide sophisticated three dimensional modeling as well as noise reduction.