研究目的
To examine the ability of a broadband free-space fNIR system in detecting high optical absorbing media resembling a human head with an embedded hematoma and to study the spatial resolution detection of a hematoma for early detection of traumatic brain injury (TBI).
研究成果
The broadband frequency modulated fNIR system shows high accuracy in detecting hematomas in multilayer brain phantoms, validated through 3D FEM modeling and experimental measurements. The novel signal processing method using derivatives of ?IL and ?IP enables identification of small hematoma sizes with high sensitivity. This approach holds promise for early TBI detection, but further work is needed for different measurement configurations and real-world applications.
研究不足
The study is performed with a fixed separation of 2 cm between optical transmitter and receiver, which may not be uniform for different measurement topologies. Further adjustments are needed for varying separations and depths. The phantoms used may not fully replicate in vivo human head conditions, and the method's applicability to real clinical settings requires validation.
1：Experimental Design and Method Selection:
The study uses broadband frequency modulation for fNIR imaging, comparing 3D FEM numerical modeling with experimental measurements. The diffusion equation is solved using FEM in COMSOL software. A signal processing method based on first and second derivatives of changes in insertion loss and phase is employed for hematoma detection.
2：Sample Selection and Data Sources:
Inhomogeneous multi-layer phantoms representing the human head (scalp, skull, cortex layers) with embedded occlusions of different sizes (0.5 cm to 2 cm diameter) to simulate hematomas. Optical properties are based on known parameters from manufacturers.
3：5 cm to 2 cm diameter) to simulate hematomas. Optical properties are based on known parameters from manufacturers.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Automatic Network Analyzer (Anritsu MS4623B), optical transmitter modules with tri-wavelength VCSELs (670 nm, 795 nm, 850 nm), optical receiver modules (APD Hamamatsu ADP module C5658), SP3T RF switch (Hittite HMC245QS16), Bias-T networks, printed circuit board with FR4 substrate, translation stages, and solid phantoms with specified optical absorption and scattering coefficients.
4：Experimental Procedures and Operational Workflow:
Optical transmitters and receivers are placed on the head phantom with a separation of 2 cm. Broadband frequency modulation from 30 to 1000 MHz is applied. Insertion loss (IL) and insertion phase (IP) are measured and compared to 3D FEM simulations. Data is curve-fitted to a mathematical model, and standard error is calculated. Derivatives of ?IL and ?IP are computed for threshold detection of hematomas.
5：Data Analysis Methods:
Standard error calculation between experimental and simulation data, curve fitting to a√frequency + b model, and analysis of first and second derivatives of ?IL and ?IP to identify frequency-stamps for hematoma detection.
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