【作者】 李鸿炜；

【导师】 颜国正；

【作者基本信息】 上海交通大学 ， 精密仪器及机械， 2009， 博士

【摘要】 针对现有消化道动力功能性疾病诊查方法的缺陷,本文在国家自然科学基金项目(编号:60875061)、国家863计划项目(编号:2006AA04Z368)、国家863计划项目(编号:2007AA04Z234)和上海交通大学“医工(理)交叉研究基金”项目资助(编号:YG2007MS21)的资助和支持下,深入研究了人体全消化道生理参数介入式遥测方法及遥测胶囊的体外无线定位技术,研制了定位精度高、抗干扰能力强、便携式的定位系统。以诊查消化道动力功能疾病为出发点,研制了能够在人体正常生理状态下监测全消化道生理参数(压力、温度和pH值)的介入式遥测系统。分析了系统的总体方案、硬件电路、MCU程序、以及数据处理软件系统的设计。通过临床试验,验证了人体全消化道生理参数介入式遥测系统的可行性。针对遥测胶囊的定位问题,提出了基于区域分割的二维射频信号强度定位法。该方法通过将人体腹部表面进行区域分割,仿真建立“区域号——体外天线接收信号强度”标定数据库。利用查表法,实现对遥测胶囊的二维区域定位。从而,解决了由于人体组织对射频信号衰减特性复杂和受试者个体差异导致的很难建立精确射频信号衰减模型这一问题;提高了射频信号强度定位法的抗干扰能力。此外,研究了射频信号相差定位法、永磁标记物定位法,以及直流脉冲定位法。通过体外实验,比较了各种定位方法的优缺点,并得出结论:这些定位方法的可行性不足。在总结以上各定位方法优缺点的基础上,提出了基于低频交流励磁的遥测胶囊定位方案:在人体腹部表面布置多个单维圆柱状励磁线圈,遥测胶囊内封装一个单维感应线圈;各励磁线圈轮流励磁,同时,在感应线圈中产生相应的感应电动势;遥测胶囊中的检测电路检测各感应电动势,并由其射频模块,将检测数据发送至数据接收器存储;最后,将存储在数据接收器中的感应电动势检测数据,导入上位机定位算法软件中,从而解得遥测胶囊位置坐标。为了建立精确的定位模型,从单个励磁线圈磁场分布模型入手,分析了等效磁偶极子模型、等效环形线电流模型、等效环形线电流的简化模型、基于场源离散化的等效载流螺线管磁场分布模型。通过比较这些模型计算磁场强度的精度,确定以基于场源离散化的等效载流螺线管磁场分布模型为基础,建立了交流励磁定位模型。为了求解由定位模型导出的非线性方程组,提出了基于表面响应模型和模拟退火算法的混合定位算法。通过仿真与传统算法相比较,得出此算法计算精度高,收敛速度较快。采用上述交流励磁定位方案,研制了便携式交流励磁定位系统。分析了系统总体结构、磁场检测子系统、体外励磁控制和数据接收子系统的设计方案,研究了系统参数的选取和优化方法。提出了基于证据理论决策的多元信息融合定位方法,并通过仿真实验验证了其可行性。搭建了定位实验台架,应用便携式交流励磁定位系统,进行了大量的体外定位实验,评价其定位精度。为了对定位结果进行误差修正,分析了多种误差修正方法:传统误差修正法、基于高阶多项式拟合的误差修正法、Hardy’s Multi-Quadrick误差修正法,提出了基于径向基神经网络的误差修正方法。通过评价各修正法对定位数据修正效果,得出基于径向基神经网络的误差修正法能够减小最大定位误差和平均误差。验证了便携式交流励磁定位系统与人体组织的电磁相容性,即定位系统对人体的是否存在辐射伤害和人体组织是否对系统定位精度存在影响。用生理盐水和猪肉来模拟人体组织,将遥测胶囊放在其中,通过磁场强度受影响评估实验和定位精度受影响评估实验,验证了生物组织对本定位系统基本无影响。另一方面,通过电磁仿真,获得了定位系统对人体的电磁辐射剂量,将其与国际人体电磁辐射安全标准相比较,验证了定位系统的人体电磁安全性。实验和仿真结果表明,交流励磁定位方案能够满足对遥测胶囊进行体外便携定位要求。而且根据此方案设计的便携式交流励磁定位系统,定位精度较高,抗干扰能力强,对人体无电磁辐射伤害。因此,本文设计的定位系统具有很高的临床应用价值。更多还原

【Abstract】 Aiming at the defects of the current method for detecting gastrointestinal motility, the thesis, supported by the National Natural Science Foundation of China (NO. 60875061), the National 863 program of China (NO. 2006AA04Z368 and NO. 2007AA04Z234), and the Combination of Medicine and Engineering (Science) Foundation of Shanghai Jiaotong University, studied the interventional telemetric method of the human gastrointestinal physiological parameters and localization technique of telemetric capsule. A portable localization system for localizing the telemetric capsule with high localization accuracy and strong anti-jamming ability was developed.For detecting gastrointestinal motility diseases, an interventional telemetric system was developed, for monitoring the physiological parameters (pressure, temperature and pH value) of the whole gastrointestinal tract under the normal physiological state of human. The whole scheme of the system, the circuits, the program of the MCU, and the data-processing software, were analyzed. By clinical experiments on human, the feasibility of the interventional telemetric system was verified.To solve the problem localizing the telemetric capsule in vitro, the 2D localization method based on region segmentation and RF signal strength, was proposed. The method segmented the region of the abdomen of human. By simulation, the calibration database of“district number and received RF signal strength”was built. Then, by the look-up-table method, the telemetric capsule was localized on 2D districts. So the method solve problem that the attenuation model of RF signal in human body cannot be built accurately because of the complicated characteristics of RF signal attenuation and the difference of the different people. And the anti-jamming ability of the localization method based on received signal strength, was improved. Besides, the localizationg method based on phase difference of received RF signal, the localization method based on permanent magnetic markers, and the localization method based on pulsed DC electromagnetic field, were studied. And by experiments in vitro, the advantages and disadvantages of the methods were compared. And a conclusion can be drawn that the methods outlined above were unfeasible for localizing the telemetric capsule.Based on the analysis of the advantages and disadvantages of the above method, 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 build the accurate localization model, analyze the magnetic field distribution model of an excitation coil, including the magnetic dipole model, the circle current model, the simplified circle current model, and the current solenoid model based on discretization of field source. By comparing the computation accuracy of the magnetic field strength with the models, the current solenoid model based on discretization of field source, was found more accurate. And with the model, the AC excitation localization model was built. 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. The multi-information fusion localization method based on D-S theory decision-making, was put forward; and its feasibility was verified by simulation.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. On the other hand, by electromagnetic simulation, the electromagnetic radiation dosages of the localization system to human were acquired. By comparing them with the international electromagnetic safety standard for huma, a conclusion was drawn that the localization system cannot cause electromagnetic hazards to human.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.更多还原