The Research Of Port Wine Stain Feature Parameters Based On Optical Coherence Tomography And Applications In The Mathematical Simulation

Port wine stains(PWS) is a congenital disease. The histopathological manifestation is the capillary dilation and malformation in upper dermis. The most effective therapy for PWS at present is vascular-targeted photodynamic therapy(V-PDT). V-PDT treatment involves the interation of multiple factors such as laser, photosensitizer and oxygen. Research on the interaction among these factors can help clinicians formulate reasonable treatment protocols. Mathematical modeling is a common method to study the interaction among the multiple factors. At present, mathematic model of the V-PDT treatment of PWS is simulated by the experience of vascular structure parameters of different pathological type. The types of PWS are always determined by the observation of the patient’s exterior color. However, according to the appearance of color is difficult to judge the real structure inside the PWS tissues. Therefore, an objective detection should be used to determine the real structure inside the PWS. Then, the mathematical model can be optimized by the actual parameters, so that the simulation results can match the true clinical practice better.With the emergence of optical coherence tomography(OCT), it has been successfully applied in many fields with its non-invasive, high resolution and high speed imaging characteristic. OCT can be used to image PWS. In addition, the image signals of OCT also carry some optical properties information of the PWS tissues. Therefore, the OCT can achieve extraction of PWS structural parameters and optical parameters of the patients to improve the establishment of PWS tissues optical model. Then, combining with mathematical simulation methods for the V-PDT, the actual clinical situations can be analyzed to guide the development of treatment programs.Firstly, based on the histopathology and ultrastructure of the PWS,the optical model of PWS which had columnar blood vessels in the epidermis was established. Then, the Monte Carlo method was applied to simulate the distribution of laser in tissue. Through the GUI design, the model parameter can be input artificially. By this simulation program, the influence of model parameters such as epidermis thickness, the diameter and depth of ectatic vessels on the distribution of radiant fluence rate can be analyzed.Secondly, the basic theory and the main parameters of the time-domain OCT were discussed. The solutions of the key technologies during the OCT system establishment were introduced. Then, the main indexes of the system were tested. The methods of extraction of PWS epidermis thickness, diameter and depth of ectatic vessels were established. The OCT data of 60 PWS positions before V-PDT and 3 months after V-PDT are collected. The structural changes of PWS caused by V-PDT were analyzed and the relationships between the structure and treatment outcome were also analyzed.Thirdly, by using the least squares method for vertical scanning signal PWS curve fitting, an optical properties extraction algorithm was developed to extract the scattering coefficient of the PWS skin. The accuracy of the algorithm was verified by the measurement of different concentration Intralipid. Then, the PWS skin was detected by the OCT during the V-PDT. The changes of PWS skin scattering coefficient was analyzed by the extraction algorithm established in our study.Finally, according to the changes of photosensitizer and oxygen concentration with time in the blood vessels and tissue, a mathematical simulation model which can calculate the singlet oxygen production in PWS was established. Based on the PWS typical structure collected by OCT, the light distribution and singlet oxygen production can be calculation during the V-PDT. Then the treatment outcome can be predicted according to the singlet oxygen production. Follow-up results were consistent with the predicted results. The effectiveness of the V-PDT for PWS mathematical simulation model can be demonstrated. The impact of PWS structure on singlet oxygen also can be analyzed. Meanwhile, the feasibility of the mathematical simulation model used to guide the development of clinical treatment plan has been preliminary analyzed.