研究目的
To propose and implement a succinct calculation using trigonometric relations to estimate optical-property coefficients (absorption and scattering) in bulky media for diffuse optical imaging, aiming to improve the initial guess for image reconstruction in applications like breast cancer detection.
研究成果
The proposed succinct trigonometric method provides a simpler alternative for estimating optical-property coefficients in homogeneous media, with better performance than some existing methods but not superior to numerical finite element solutions. It facilitates system calibration and initial guess for image reconstruction, with future work needed on absolute property recovery and handling measurement variances.
研究不足
The method assumes homogeneous and infinite media, but real phantoms have finite boundaries, leading to intrinsic differences in measurements. System calibration using intercepts is not fully implemented, and there is variance in fitted data that requires tolerance bands. The estimation errors range from 0-14.81% for μa and 20-42% for μs', indicating room for improvement in accuracy.
1：Experimental Design and Method Selection:
The study uses a frequency-domain photon density wave (PDW) experiment based on the diffusion equation for homogeneous infinite media. A trigonometric identity is applied to simplify the calculation of slopes from measured data.
2：Sample Selection and Data Sources:
Two types of phantoms are used: a tank-type phantom (195 x 145 x 155 mm) and a cylinder phantom (?50 mm), both filled with Lipovenoes at concentrations of 1.25% and 2.5% to mimic homogeneous media.
3：25% and 5% to mimic homogeneous media.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes a function generator, splitter, coupler, laser diode (824 nm), photomultiplier tube (PMT), pre-amplifier, two mixers, PC with DAQ board, optical fibers, and liquid light guide (LLG). Materials are Lipovenoes phantoms.
4：Experimental Procedures and Operational Workflow:
NIR light from the laser diode modulated at 20 MHz is introduced into the phantom via an optical fiber. Photon intensity and phase data are collected at various source-detector separations using the LLG and PMT. Data are fitted to linear equations to extract slopes for estimating optical properties.
5：Data Analysis Methods:
Slopes (m_ac, m_θ) from fitted data are used in trigonometric relations (Eqs. 6-9) to compute μa, D, and μs'. Errors are analyzed by comparison with analytical solutions.
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