A Time Domain Non-Contact Near-Infrared Optical Tomography System

Compared with the current breast imaging methods such as mammography, ultrasonic imaging and nuclear magnetic resonance, diffuse optical tomography (DOT) becomes one of the most promising breast imaging technique due to its advantages of good specialty, sensitivity and safety. Based on the technology of DOT, fluorescence diffuse optical tomography (FDOT) introduces Indocyanine Green (ICG) as fluorescence enhancement agent, which can greatly improve the image contrast. Tumor-to-normal tissue contrast based on FDOT with the fluorophore Indocyanine Green is two-to-four-fold higher than contrast obtained with traditional diffuse optical tomography. FDOT can not only reconstruct the yield but also the lifetime, which improves the accuracy of early cancer diagnosis and provides functional information for the early cancer diagnosis.Conventionally, tomography imaging systems require the use of a number of detector fibers put in contact with the object of investigation, which limits the data scale and the improvement of spatial resolution. In order to solve above problems, a time domain noncontact fluorescence tomography system towards the early diagnosis of breast cancer is developed. The time domain system based on the time-correlated single photon counting technique (TCSPC) is adopted to provide both the high sensitivity in detection and good capability in multi-parameter reconstruction. Compared with the conventional contact measurement mode, the noncontact system with light scanning can provide more measurement data for improving the spatial resolution of the images. The controlling software is developed on the platform of Visual Studio 2008 integrated with Qt and the functions of continuous measurement and real-time display of the measurement curves are realized.The performance of the system is evaluated with measurements on solid phantoms. In the DOT experiment, both the absorption coefficient and the scattering coefficient can be well constructed. The reconstructed value is corresponded to the real value and the reconstructed position and size of the target can well reflect the real position and size; In the FDOT experiments, for the phantom with single fluorescent target, the fluorescence yield and lifetime were simultaneously reconstructed with good quality. For the phantom with two fluorescent targets, the targets with the center-to-center separation of 20mm and the edge separation of 15mm can be distinguished. Measurements also show that the reconstructed yields are linear to the concentration of the fluorescence dye. The results demonstrated the potential of the system in the in vivo diagnosis of the early breast cancer.