Research On Modeling Of Human Tooth And Skin Tissues Optical Coherence Tomography Imaging And Its Applications

Optical coherence tomography is a noninvasive imaging method which provideshigh resolution images of the internal tissue structure based on the principle of lowcoherent interferometry. With the applications of OCT in more and more fields, themodeling of OCT imaging is becoming important and valuable, and has been appliedin imaging of blood vessel, corneal and retina, to make prediction/interpretation ofOCT imaging results. Now OCT technology has been applied to dentistry anddermatology, and have been used to study dental caries diagnosis and glucose sensing.An accurate simulation tool is very important for the practical application of OCT indentistry and dermatology. However, few studies are dedicated to the modeling oftooth and skin tissues OCT imaging, and applied to research on diagnosis of diseases.In this dissertation, OCT imaging models of human tooth and skin tissues areestablished based on the optical properties of tooth tissue and skin tissue with MonteCarlo method. The geometry and the optical parameters of the models are chosen onthe basis of the experimental OCT images. Moreover, the two imaging models areapplied to the study on quantitative assessment of early caries and sensitivity of bloodglucose sensing with OCT, respectively. The main research contents and innovativepoints are shown as follows:1. Models of tooth OCT imaging are set up whose geometries are consistentwith the organizational structure of teeth. The implementation of the model consistsof two parts: the simulation of a Gaussian beam with hyperbolic characteristics, andsimulation for photon propagation in tooth tissue based on the OCT theory and opticalproperties of tooth tissue. Simulated OCT signals and two-dimensional simulatedOCT images of single tooth enamel, dentin and two-layer tooth tissue withnon-parallel surfaces are obtained. Moreover, the followings are analyzed: thecontributions of various photon fractions to the simulated OCT images of the tooth,the effect of system parameters on the OCT image, the effect of focus positions andthe non-distorted imaging depths of three kinds of tooth structure.2. A quantitative evaluation method for caries degree of the enamel based onthe OCT method is presented. The optical parameters of sound enamel and cariousenamel with different demineralization time are extracted, by employing a combination of the OCT imaging model of early artificial enamel caries on thesmooth surface, and the OCT detection experiment of artificially enamel caries invitro. The relationship between the scattering coefficient of enamel anddemineralization time is gained. The effect of carious enamel with differentdemineralization time on the non-distorted imaging depths of the enamel is analyzed.3. The OCT imaging model of skin tissue is established. The numericalsimulation of the skin tissue OCT signal is implemented, and the non-distortedimaging depth of skin tissue is studied. The Monte Carlo model of glucose sensingwith OCT is presented based on the imaging model of skin tissue, and it is applied tothe predication of the OCT signals corresponding to different glucose concentration,and analysis of the sensitivity of OCT signal to variations in the glucose concentration.The results are compared with the ones of OCT testing based on Oral GlucoseTolerance Test (OGTT). Experimental and simulation results indicate that Themaximum correlation of the OCT signal slope with glucose concentration is observednear papillary layer and the border of papillary and reticular layers.