Research On Multi-wavelength Dynamic Diffusion Optical Tomography

Diffusion Optical Tomography(DOT)is a novel functional imaging technique with the advantages of non-radiation,non-invasive and providing physiological information,which shows the potential application prospect in Breast cancer screening.It can recover the distributions of the internal optical parameters and biochemical parameters by utilizing the high penetration depth of near-infrared light in tissueCompared with the traditional static DOT imaging,dynamic DOT can obtain temporal and spatial hemodynamic information as while as acquiring internal structural information and physiological function information.As an important source of imaging contrast,the dynamic information can be used to improve the quality of static imaging,and also to reflect the physiological information of tumors which is helpful for the monitoring,localization and treatment of tumors.In order to accurately capture the dynamic process of hemodynamics,the technical difficulties that dynamic DOT needs to solve include:(1)The imaging system must have a sufficiently high temporal resolution to acquire reconstructed images at high speed.(2)In order to detect weak changes in different states,enough sensitivity is required.(3)Good spatial resolution for breast tumor screening and diagnosis.For solving the above-mentioned problems,this paper develops a multi-wavelength continuous wave dynamic diffusion optical tomography system.The system consists of a total of 96 sources at three wavelengths(685 nm,785 nm and 830 nm)and four large dynamic range photodetectors.The system realizes parallel excitation and detection of20 light sources by combining high-concurrency phase-locked photon counting technology and flexible optical switch,which greatly improves the measurement speed and sensitivity of dynamic DOT.In order to verify the feasibility and effectiveness of dynamic DOT,we conducted a series of evaluation experiments and phantom experiments.First,the stability,crosstalk,the ability of anti-interference and the dynamic range of the system were assessed.The experimental results showed that the coefficient of variation of the light source is almost less than 1%,the crosstalk between channels is less than 2% and the system’s dynamic range is up to 109 d B.The phantom experiment verified the abilities of sensitivity,3D reconstruction,dynamic imaging and spatial resolution.The results showed that the system can distinguish the target with the absorption contrast as low as1.2 and reconstruct 3Dimages.Furtherly,the dynamic experiments showed that the system can track the dynamic changes of the absorption coefficient at speeds up to 2s/frame.In addition,the rotation measurement experiment demonstrated the capability of improving the spatial resolution.These experimental results prove that the system developed in this paper can meet the requirements of dynamic DOT measurement.