Modeling And Implementation Of The Magnetic Propelled Endoscopic System

Capsule endoscope is an examination of the gastrointestinal track using a wireless capsule endoscope which contains digital camera, ASIC transmitter, antenna, illuminating LEDs assisted imaging, and battery. Capsule endoscope with the size of a normal pill can be easily swallowed by patients in various ages. It takes pictures throughout the gastrointestinal tract by sending images to an external recorder and thus provides useful information for clinic diagnosis of gastrointestinal tract diseases.However, recent products of capsule endoscope still have some problems: (1) no external guidance control system; (2) time and money consuming; (3) unable to conduct on-time treatments such as drug delivery and body tissue collection. The movement of the capsule depends solely on the peristalsis system. Therefore, it takes 6-8 hours for an examination and doctors cannot perform a pinpoint analysis once an irregular vision has been found. In addition, camera in capsule takes thousands of photos in every part of the tract to prevent the possibility of missing an important picture. Therefore, hours of time are needed for doctors to organize and analyze a large number of images, still with a 60-70% rate of success in diagnostics. All of these drawbacks render capsule endoscopy extremely high in cost but extremely inefficient in terms of time spent and resources used.This paper investigates design, modeling, simulation, and control issues related to self-propelled endoscopic capsule navigated inside the human body through external magnetic fields. A novel magnetic propulsion system is proposed and fabricated, which has great potential of being used in the field of noninvasive gastrointestinal endoscopy. Magnetic analysis model is established and finite elements simulations as well as orthogonal design are performed for obtaining optimized mechanical and control parameters for generating appropriate external magnetic field. Simulated intestinal tract experiments are conducted, demonstrating controllable movement of the capsule under the developed magnetic propulsion system.SectionⅠreviews the state-of-the-art technologies in the field of capsule endoscopy. SectionⅡestablishes fluid dynamics model suitable for micro-machine's movement in intestinal tract, simulates pressure distributions of micro-machine's surface, and further calculates driving and load torques. Based on the fluid simulation results, parameters for generating appropriate rotating magnetic field can be calculated. Frictional resistance model is also embodied which takes the consideration of pressure of the external organ and visco-elastic characteristics. Finite elements simulations as well as orthogonal design are performed for obtaining optimized geometry design of the capsule. The fluid dynamics and contact mechanics simulation methods provide a novel approach to analyze biomedical micro- machine's mechanical properties under external electromagnetic equipment.SectionⅢfocuses on the design and integration of a magnetic propulsion system for specific application of active locomotion control of the endoscopic capsule. Engineering design of the magnetic propelled endoscopic system is performed. A novel magnetic propulsion system is proposed, which has five coupling axes and can realize capsule endoscope's multi-direction movement in the gastrointestinal tract. The integration approach of the endoscopic system involves camera lens, CMOS sensor, microcontroller, RF transmitter, antenna, LEDs, button cells, and magnetic shell. The microsystems integration of the capsule endoscope is based on commercialized chips and devices available on the markets, rendering the total costs of the endoscopic capsule less than 5 dollars with power supply up to 120 mW and dimension of ?12mm×34mm. A custom-made magnetic shell is applied to the capsule externally in order to make the capsule responsive to the magnetic field generated by a magnetically steering system designed specifically for active locomotion control of the developed capsule endoscope. The magnetic-steered endoscopic capsule system is proven to be appropriate to achieve the speed of 10mm/s on average and go through the simulated gastrointestinal tract (? 20mm×1600mm) within 3 minutes.SectionⅣdescribes the in vitro experiments being carried out in the transparent polyvinyl chloride tube with and without intestinal layer. The dimension of the simulated intestine is ?20cm×160cm and it includes 6 regions which represent different combination of straight and curved paths. The result suggests the feasibilities of steering the endoscopic capsule's location and orientation by the developed magnetic propulsion system. However, further investigations should be carried out for improving the current system in two aspects: 1) External image visualization unit is necessary as the supplementary component of the magnetic propulsion system for providing position information of the capsule. 2) Fluidic medium of the gastrointestinal tract and the closed forms of the human body should be taken into consideration for simulating the actual environment of the capsule inside the body cavity under external magnetic equipment.