Research On Invitro Magnetic Tracking Location Technology For Telemetric Capsule

In order to determine the position of an intra-body microcapsule, supported by the National 863 program of China (NO.2006AA04Z368), the thesis is based on the noninvasive detecting system for human gastrointestinal tract, developmented by Shanghai Jiao Tong University to detect physiological parameters of human digestive tract, such as the pH value,temperature,pressure and electrogastrogram capsule. The thesis exploitats a method to detect magnetic field outside human body based on the Hall Effect, and tries to find a magnetic,localizing method which is feasible,practical and portable in principle.Campared the advantages and disadvantages of several analysised methods, it is found that the magnetic location method based on Hall Effect possesses such good features: non-contact,rapid and simple-applicated. Based on analysis the distributing rule of permanent magnetic field, this paper proposes the magnet field tracking technology outside human body, which is based on permanent magnetic field and the Hall Effect sensor array, and designs a magnet field tracking system outside human body. The system's work flow is as follow: first, a tiny magnet, as a magnetic source, is placed in the micro medical device, which is used to detecting human gastrointestinal tract; second, Hall Effect sensor array is composed by the hall linear sensor, placed outside of patients body to detect the magnetic field information of the micro medical device entered into human body; and then, these information is processed by the control module, composed single chip microcomputer control(SMC),multi channels chosen circuit,a programmable amplifier(PGA) and AD converter AD7321; and at last, the results can be gotten by the arithmetic based on magnetic dipole model. Calculating the position of permanent magnetic achives the goal in determining the spatial position of micro medical device in vivo.At present, a magnet field tracking system outside human body, which is based on the Hall Effect sensor array, has been proposed. In this paper, system optimizational experiment,system performance experiment and the simulation experiment of intestine plane are designed to vetified the feasibility and accuracy of this system and the precision of location results. The experimental results indicate that the positioning accuracyof of magnetic location method reaches millimeter level, and the absolute error of method is controlled within 18 millimeter, the percentage of measuring point, whose relatiue error ranges between±15mm, is more than 95%. So the precision of this method is satisfactory and adequate for practical use, and this system can precisely track the location of the tiny magnet. As an untouched,low-cost, easy-cooperate and high-precision measurement, it provide a foundation for the further study in the accurate positioning of intestinal tract. How to describe the spatial position of micro medical device in human digestive tract directly and effectively will be the key point which our next research focus on, and in this foundation's improvement needs further research.