为了提高电磁定位系统的定位精度、稳定性及抗干扰性,本文提出了一种基于相位差的电磁跟踪方法.在对方法的可行性进行了验证的基础上,设计实现了采用了C/S体系架构的电磁定位系统并进行了初步的测试.测试结果表明该系统的平均位置误差为0.104 7±0.000 6 cm,平均姿态误差为0.268 7°±0.028 7°.在1 kHz的激励信号下,该系统最快定位速度可达到3.5 ms.可见,基于相位差的电磁定位系统具有较高的定位速度和定位精度,同时具有较高的稳定性,经过进一步的优化可满足多种场景,包括介入式微创手术的定位需求.

This paper realized an electromagnetic tracking system based on electrically-controlled rotating magnetic field. A tracking system using the digital signal processor (DSP) as the control processing device was developed, including a controllable constant current source module, a magnetic field source module, a three-axis magnetic sensor and ADC interface circuit. The experimental results verified that each time the system could be stable positioning, average error of position was 0.282 cm, the average error of orientation was 0.696o, the positioning time was 1.572 s. Through calibration and further improvement of the hardware circuit, the performance of the system is expected to further improve.

In this paper, an electromagnetic tracking method based on fast determination of the maximum magnetic flux density vector (MMFDV) represented by two azimuth angles is proposed. The system designed to validate this method includes two magnetic sources and a 3-axis magnetic sensor. Each source consists of three mutual orthogonal coils. The main characteristic of this method is that the direction of MMFDV generated by a magnetic source can be determined as long as each coil of the source is excited once. Then the sensor can be located with a noniterative geometrical algorithm in real time. This method is easy to be implemented and can realize tracking in full coordinate space. Simulation and experimental results demonstrate a good performance of this method. It can be used as a part of computer-assisted navigation system in minimally invasive surgery after proper optimization.

目的 针对传统电磁跟踪方法存在的依赖磁场模型具体磁感应强度值、迭代算法繁琐的问题,提出一种采用非迭代几何算法的电控旋转磁场跟踪方法,以避免模型误差、简化定位算法.方法 采用三轴正交磁场源,通过控制磁场源三轴激励电流强度实现合成最大磁感应强度矢量在空间中遍历旋转,根据矢量指向三轴磁传感器时的旋转角利用非迭代几何算法进行定位,对该方法进行了仿真研究.结果 仿真半径为0.3m时,平均位置误差为0.32 cm,方差为0.02,定位时间为0.54 s.结论 基于电控旋转磁场与非迭代几何算法的电磁跟踪方法可以较准确地定位传感器,具有定位速度快、性能稳定的潜在优势,值得进一步优化提高性能以满足介入式微创手术临床实用要求.

The objective of this study is to explore the possible ways to reduce defibrillation energy and further reveal the mechanism of electric defibrillation. A bidomain simulation study was performed on a rabbit whole-ventricle electrophysiological model and the feasibility of the defibrillation strategy with multi-electrodes stimulation was verified. Simulation results indicate that the new approach is effective in low-energy defibrillation.

This paper presents an electromagnetic tracking method based on two electrically-controlled magnetic sources. Each source consists of three mutual orthogonal coils. The method can skillfully determine the rotation angles of the maximum magnetic flux density vector (MMFDV) generated by a magnetic source according to the Biot-Savart Law. Then the position of the sensor can be calculated with a noniterative geometrical algorithm in real time. Simulation results demonstrate a good performance of this method.

目的 探讨多功能心脏电生理刺激记录仪的临床应用.方法 应用多功能心脏电生理刺激记录仪(DF-5A型)对1026例被检查者(包括2008年6月至2013年6月在苏州大学第一附属医院门诊、急诊及病房等就诊者),行经食管心房调搏术(TEAP),其中男性362例,年龄:15～85岁.结果 1026例被检查中,912例因“阵发性胸闷心悸不适”行TEAP,695例拟诊阵发性室上性心动过速(PSVT);217例拟诊窦房结功能不良,67例因PSVT发作,为中止PSVT;另有47例因不能配合而拒绝TEAP.695例拟诊PSVT者中,TEAP诱发并终止PSVT 278例(房室结双165例,旁道113例);64例被检查者存在房室结双径路,但未能诱发PSVT.217例拟诊窦房结功能不良者,仅20例符合窦房结功能不良,且大多为老年人.53例被检查者在检查过程中分别出现短阵房速、房扑或房颤,其他被检查者为见明显异常.结论 DF-5A型多功能心脏电生理刺激记录仪给临床医生提供了有效、安全和方便的诊疗措施.

This paper introduces the design and implementation process of a multifunctional recorder for cardiac electrophysiology stimulation based on an embedded system. The front-end circuit which is composed of a deifbrillation voltage protection circuit and an electrostatic protection circuit and high-voltage circuit which is composed of a boosted circuit of transformer-coupled and single-ended lfyback MOS switch and a high voltage regulator circuit are controlled with Darlington optocoupler switch to maintain the stable pulse output waveform. The isochronous and real-time collection, displaying and storage of 12 lead and esophageal lead electrocardiogram can be implemented through the connection between the computer and the recorder with the USB interface. The examination and recording process of cardiac electrophysiology has been optimized effectively with the recorder which has integrated various operation and analysis functions for clinician.

The electrical shock is the only useful method to terminate the ventricular fibrillation (VF). The low energy defibrillation research is very important. The relationship of the shock parameters and the defibrillation efficiency will be investigated in this study. The mechanism of electrical defibrillation is that most of the myocardium cells can be enforced to depolarize and enter to refractory period at the same time when electrical field of the shock interacts with myocardium. The change of trans-membrane potential depends on the trans-membrane current. The defibrillation voltage is only the method to produce the needed current. The voltage needed to defibrillation lies on the defibrillation impedance. Energy is the product of the voltage and current and more easily influenced by the impedance and the current distribution. The effects of pulse duration to defibrillation threshold need to be considered also. Generally, the change of trans-membrane potential to reach the depolarization ΔEm is constant. Then I × τ (pulse duration) is a constant too. So cell's depolarization depends on the quantities of charge (the product of current and time) injected to the cell. Totally 7 domestic swine had been used for animal trails and more than 300 times VF had been induced. Defibrillation threshold is the lowest dosage of the shock for successful defibrillation. The animal trails show that the charge threshold varies little when the pulse duration is short but it will increase quickly at an certain pulse duration. We think that electric charge Q is the main parameter to determine the defibrillation result. The energy threshold is diverse because it maybe influenced by many reasons. So the energy threshold can be used to evaluate the ways and means of defibrillation, but not suitable to be used as the defibrillation dosage. © 2013 Springer-Verlag.

目的 提出一种不依赖磁场分布模型且采用简单几何方法求解的双磁棒旋转搜索定位/跟踪方法.方法 设计基于数字信号处理器(digital signal processor,DSP)的双磁棒旋转搜索定位/跟踪系统,对双磁棒旋转搜索定位/跟踪方法的可行性进行初步验证.结果 平均位置误差为0.954,平均姿态误差4.86°.结论 双磁棒旋转搜索定位/跟踪系统有很好的稳定性,搜索速度和定位精度还需进一步提高.

Automatic external defibrillator(AED) is independently designed and developed and evaluated ventricular tachycardia(VT/VF) recognition sensitivity,specificity and defibrillation effect through animal experiment.The result shows that this device has advantages of convenient carrying,fast operation and accuracy,and has higher recognition sensitivity,specificity and defibrillation effect.

In this paper, an electromagnetic tracking method that uses two rotating orthogonal coils is proposed. Two cross-shaped coils can rotate together and be driven in sequence to generate a magnetic field. One of the rotating orthogonal coils is used to track the position of the three-axis sensor and the other is to help solve the orientation of the sensor. As rotation can provide a geometrical relationship between the magnetic source and the sensor, the method does not require the generated magnetic field to imitate the ideal dipole in calculation. A fast noniterative algorithm and simple 1-D mapping along the axis of one coil are used to realize six degree-of-freedom (6DOF) tracking. Thus, the complexity of the magnetic tracking method and the corresponding system can be greatly reduced. Simulation results show that the method has good tracking accuracy and speed, which can be further improved by using an adaptive step-size searching strategy. So, it is concluded that the method can be used as an effective target monitoring method in many application domains such as minimally invasive therapy.

Objective Non-excitatory electrical stimulus during the absolute refractory period is called the cardiac contractility modulation(CCM).The changes of calcium handling by CCM signal were computationally studied.Methods The current electrophysiological model of human ventricular cell was altered to simulate the failing cell.Results The falling heart cell had very consistent action potential and intracellular calcium concentration in agreement with clinic findings.The activation of sodium-calcium exchanger was greatly strengthened by CCM signal and more calcium enters cell through it.CCM gradually increased the peak calcium concentration in the sarcoplasmic reticulum,which would release more calcium in sequent cardiac cycles,until a balance state was reached and kept.The prolonging of action potential duration by CCM signal was very accordant with the enhancing of calcium handling by the CCM signal.Conclusion CCM could change the calcium handling,increase the free calcium concentration in cells,so to enhance the contractility.

Objective By using non-iterative algorithm,to propose and verify a novel non-model-based electromagnetic method for tracking the position and orientation of instruments inside the human body during the minimal invasive operation.Methods The proposed method was realized by rotating 2 coils outside human body to search for the position of a minimal 3-axis orthogonal magnetic sensor inside body,with maximal magnetic flux density.The orientation of the sensor could be calculated from the relationship between the coordinate frame of the sensor and that of the coils based on the direction of magnetic flux densities along the axis of the coils.The simulation experiment was used to evaluate the error performance and the tracking performance of the system.Then the real performance of the method was evaluated by in vitro experiments.Results Experimental results showed that the averaged position error was 1.387 cm and the averaged orientation error was 5.023° within the tracking region of 40 cm.It was also shown from the simulation that a higher resolution might be obtained.Conclusion Therefore,the proposed method can effectively satisfy the requirement of the navigation in the minimally invasive operation with a simple algorithm and thus has a good prospect in application.

临床动物电击除颤实验无法精确测量放电电场在心脏上的实际分布情况,且存在诸多不便利和不安全因素。鉴于此,提出了一种基于心脏建模及有限元求解的心脏除颤电场分布仿真研究方法,心脏模型包含了完整的心房心室解剖结构和左右心腔,考虑了心肌细胞和血液的电阻率,然后采用有限元方法进行分析,并使用Abaqus集成环境进行求解,求解结果与文献报道的参考标准进行对比。仿真结果在除颤电压阈值和能量阈值方面与目前的植入式心脏复律除颤器（ICD）的临床应用效果具有相当的吻合度,能量阈值相对误差仅为10%,验证了所提出方法的可行性。

Electromagnetic tracking is a method to track the position and space attitude of objects utilizing electromagnetic field. In this paper, the main methods during the development of Electromagnetic tracking are summarized and classified according to the magnetic field generation method, the number of magnetic sources and sensors used, the configuration and geometry of them. Tracking algorithm and calibration methods are also discussed. The critical issues during the development of electromagnetic tracking are analyzed, with the hope of helping the further research and application of electromagnetic tracking.

Objective The research objective of this thesis is to build up an experimental platform of programming and telemetry system for cardiac pacemaker as well as to find a more efficient system scheme.Methods The system consists of computer interface,FPGA development board and hardware circuit of wireless transmission.Disoussion This thesis focuses on the design of the former two parts.The computer interface realizes sending out programming command and displaying telemetry data.The FPGA development board functions as the external programmer and the cardiac pacemaker,which realize the encoding,decoding and error control of the programming and telemetry data.Conclusion The system presents a new pulse position modulation method,multi-bit PPM,by which to generate the transmitting pulse can increase the efficiency of wireless transmission and prolong the lifetime of cardiac pacemaker.The feasibility of the method is verified on the experimental platform.

Electrophysiological stimulator is widely used in study of biological electrical activities. This electrophysiological stimulator is capable of outputting both biphasic and monophasic waveforms with amplitudes within 0V and 30V. The sequence of the biphasic waveforms is alterable and their widths and interval can be respectively arbitrarily modified by the operator. The machine will inform the operator as soon as the charge completes through the indicator and buzzer. The safety of experimental objects is guaranteed by float ground thanks to battery power supply.

This thesis presents a new wireless data transmission method of implantable devices,which realizes two-way communication between implantable device and external programmer by using RF electromagnetic wave as Transmission medium.The "bit-by-bit" telemetry mechanism may reduce the power consumption of pacemaker and other implanted devices and prolong the lifetime.

Action potential duration restitution (APDR) is thought to be relevant to the stability of cardiac electrophysiology. Ventricular fibrillation (VF) was simulated using the Wei-Harumi model by taking into account piecewise linear action potential duration restitution based on clinical findings. We found, in the simulation, that heart model with steeper slope of APDR required less ectopic stimuli to trigger VF. This result suggested that the APDR may affect cardiac vulnerability to VF.