Near-Infrared Tomography Depth Correction and Sparsity
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Solution Overview
Problem
Reflection-type continuous-light diffuse optical tomography (DOT) faces challenges in accurately estimating the depth of activity sources and spatial resolution due to sensitivity attenuation and spatial blurring, leading to ill-posed problems and difficulty in obtaining three-dimensional information of local optical characteristic-changed regions inside objects, such as the brain.
Innovation Solution
An object observing apparatus that corrects for sensitivity attenuation with depth and employs sparse estimation to improve space resolution, using a combination of sensitivity information storage, correction units, and sparseness application to accurately reconstruct three-dimensional optical characteristic-changed regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If reflection-type continuous-light measurement is used, then measurement cost is reduced and sampling frequency is increased, but measurement precision and ability to estimate depth are deteriorated
Solution Approach 1:
The invention changes the measurement parameters by using multiple wavelengths of light and applying frequency-domain modulation. By modulating the light source at different frequencies and measuring phase shifts and amplitude changes, the system extracts deeper information about the tissue optical properties, thereby improving depth estimation accuracy while maintaining continuous-light measurement advantages
Solution Approach 2:
The invention introduces an intermediary processing layer that uses differential measurements and mathematical modeling to compensate for the limitations of reflection-type measurement. By comparing measurements at different wavelengths and applying diffusion theory models, the system reconstructs three-dimensional optical property distributions, enabling accurate depth estimation without requiring transmission geometry
2Ease of operation
If probes are arranged at intervals of approximately 3 cm, then ease of operation is improved, but measurement precision and spatial resolution are deteriorated
Solution Approach 1:
The invention transitions from two-dimensional topographic mapping to three-dimensional optical property reconstruction by utilizing time-resolved or frequency-domain measurements. This additional dimensional information (temporal or frequency domain) enables depth resolution, allowing accurate localization of optical property changes in three dimensions even with sparser probe arrangements
Solution Approach 2:
The invention changes the measurement parameters by using multiple wavelengths and frequency-domain modulation to extract additional information from each probe pair. This enables the system to achieve higher spatial resolution through improved signal characterization rather than through increased probe density
3Measurement precision
If high-density probe arrangement is used, then spatial resolution is improved, but device complexity and measurement cost are increased
Solution Approach 1:
The invention changes the measurement parameters by utilizing multiple wavelengths and frequency-domain modulation to extract more information from each measurement channel. This parameter diversification allows the system to achieve high spatial resolution with fewer probes by improving the information content per channel rather than increasing channel count
4Device complexity
If sensitivity attenuation with depth is not corrected, then device complexity is reduced, but measurement precision is deteriorated
Solution Approach 1:
The invention applies preliminary correction for sensitivity attenuation with depth through pre-computed correction factors or lookup tables based on diffusion theory models. By preparing these correction parameters in advance, the system compensates for depth-dependent sensitivity variations without requiring complex real-time calculations, thus maintaining measurement precision while limiting computational 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 apparatus effectively estimates local optical characteristic-changed regions inside objects with improved depth accuracy and spatial resolution, enabling precise brain activity observation and breast cancer detection.
Implementation Method 1
near-infrared light does not penetrate a living body because it is extensively scattered inside the living body
Implementation Method 2
light reflected by diffusion is observed using light-receiving probes
Data Source
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AI summary
In order to solve a problem that a local optical characteristic-changed region inside an object cannot be accurately estimated, an object observing apparatus includes: a light intensity information acquiring unit that acquires light intensity information received by each light-receiving probe in a case where light with a certain light intensity is transmitted from each light-transmitting probe of a near-infrared measurement apparatus to an object; a light intensity change information acquiring unit that acquires, for each probe set, light intensity change information regarding a light intensity change, from reference light intensity information and light intensity information; an estimating unit that acquires three-dimensional optical characteristic-changed region information regarding a position with a light absorbance change inside the object, using the light intensity change information; and an output unit that outputs the optical characteristic-changed region information; wherein the estimating unit includes: a correcting part that performs correction according to sensitivity attenuation in accordance with a depth, using sensitivity information; and a sparseness applying part that introduces sparseness for improving a space resolution, thereby acquiring the optical characteristic-changed region information. Accordingly, it is possible to accurately estimate, as three-dimensional information, a local optical characteristic-changed region inside an object.