Research On Localization Techniques Of Interventional Telemetric System

In order to determine the position of an intra-body microcapsule, the thesis, supported by the National Natural Science Foundation of China (NO. 60875061 and NO.30800235), the National 863 program of China (NO. 2006AA04Z368 and NO. 2007AA04Z234), is proposed based on low-frequency AC excitation positioning solution.Based on the analysis of the advantages and disadvantages of several methods, a method for localizing the telemetric capsule based on low-frequency AC electromagnetic field was put forward. In the method, several excitation coils were placed on the abdomen of people, and an induction coil was encapsulated in the telemetric capsule. When localizing the telemetric capsule, the excitation coils were excited with alternating current alternately. And meanwhile, the induction coil detected the electromagnetic field strength produced by each excitation coil, and transmitted the measurement results to the data receiver in vitro to store. Finally, the stored measurement results were uploaded to the software of localization algorithm, and then the position of the telemetric capsule can be acquired. To solve the nonlinear equations deduced from the localization model, the hybrid algorithm, based on the surface response model and simulated annealing algorithm, was proposed; and proved that compute fast and accurately.A portable localization system based on AC excitation was developed. The system was analyzed from the design of system structure, subsystem for detecting magnetic field, subsystem for excitation control and data receiving, and optimization method of system parameters.A test-bed for localization experiments was build. From the results of localization experiments with the portable AC excitation localization system, the localization accuracy was evaluated. To calibration the localization results, the methods of error correction were studied, including the conventional method, high order polynomial fit method, Hardy's Multi-Quadrick method. So the calibration method based on RBF neural network was proposed, and proved that the method can minimize the maximum localization error and mean error.The electromagnetic interaction of the AC excitation localization system with the human tissue was studied, which included the possible electromagnetic radiation of the localization system and influence of the localization accuracy by human tissue. Two experiments were designed to verify the influence of the localization accuracy by human tissue, in which pork and physiological saline were used to simulate the human tissue.From the results of experiments and simulation, the AC excitation localization method can satisfy the requirements for localizing the telemetric capsule in vitro. And the portable localization system based on the method, were verified that it achieved high localization accuracy, strong anti-jamming capacity, and no electromagnetic radiation hazard to human. Thus, the localization system developed in the thesis has great clinical practical value.