A Study On Laminar Optical Tomography For The Detection Of Early Cervical Cancer

Cervix cancer is the second most common cancer among women, which severely threatens women's life. While the cervix cancer is curable by early diagnosis. This thesis focuses on the early cervical cancer diagnosis system based on the laminar optical tomographic(LOT). LOT is a newly developed mesoscopic imaging system, which is categorized between the imaging technology of macroscopic and microscopic scales, depending on their spatial resolutions, and penetration depth. Considering the short source-detector separation(SDS) between ~0 to ~2mm adopted in LOT, less-scattering light can be detected to obtain a higher spatial resolution than that of the diffuse optical tomography(DOT), while imaging depth is restricted to the millimeters scale. The above features of LOT make it suitable to be applied in the early cervical cancer diagnosis system.LOT uses a system based on a confocal microscope design to achieve the non-invasively raster scan, instead of using contact-based fibers for delivery and collection of light in most DOT systems. In LOT, a linear array PMT, taken as the detector for diffuse light, collects light coming from several successive equally spaced distances away from the illuminated point at each scanning spot. This way, 3D distribution corresponding to the object's structure can be reconstructed with the 2D raw images of different SDS obtained by plane scanning. This system is mainly composed of steady-state laser of 623.8nm generation & collection subsystem, weak diffuse light detecting subsystem, and scan & control subsystem. To synchronize the raster scan and multiple-point collinear detection at each scanning spot, the system is intergraded by the software based on the X86 platform, communicated by PCI bus, which achieve a scanning speed of ~1fps(30 × 30 pixels over a 2mm square field of view), and real time monitoring on raw images.Firstly the phantom was used as the object to validate the established LOT system, the mean values of detected diffuse light from different SDSs at all scanning spots were compared to that of Monte-Carlo(MC) simulations. Results show that the maximum relative error is less than 11.6%. In addition, the limit detecting depth of 2.4mm and spatial resolution of 200?m with fixed depth was verified, respectively, which meets the need of system designation.In the earlier experiments on humans, we chose the opisthenar as the object for rich in superficial blood vessels. The raw images truly display the skin tissue information of different depth, and clearly reveal the vessel distribution at the selected depth. Next, the detected raw images will be adopted to reconstruct the distribution of tissue optical properties to obtain the functional information about tissue.