Research On Design Method And Driving Principle Of Magnetically Controlled Capsule Endoscope With Multiple Biopsies For Colon

Capsule endoscopy with small size and small invasion in digestive endoscopy has become the trend of future development.At present,capsule endoscopy in clinical use mainly relies on gastrointestinal physiological peristalsis to passively check the digestive system,which lacks repeated observation of tissue parts and has the problem of missed detection.In addition,only the image information provided by the capsule is unable to accurately identify the physiological characteristics of the diseased soft tissue,and further pathological analysis needs to be carried out through biopsy sampling.In particular,multiple biopsies are often required for colorectal cancer tissues.In view of the above problems,this paper takes the design of magnetically controlled active capsule endoscopy for multiple biopsies in the colon as the research goal,and proposes a new biopsy sampling mechanism for high-speed rotating cutter cutting the soft tissue of the inner wall of the colon,which breaks through the design difficulty of using multiple biopsies once,and realizes the active motion control of the capsule endoscopy through the external magnetic field drive method.Firstly,aiming at the problems of soft tissue in colon inner wall and unreliable capsule positioning,the idea of cutting soft tissue by high-speed rotary cutter was proposed to achieve reliable biopsy sampling,and the transmission mechanism of highspeed rotary sampling driven by compression torsion spring was designed.At the same time,according to the design requirements of multiple biopsy,a biopsy storage scheme based on the motion inertia of the cutting soft tissue is proposed.A self-centering multiple trigger structure is proposed and designed,and the influence of trigger force in the trigger process is analyzed theoretically.A prototype of multi-biopsy magnetic controlled capsule endoscopy was built,and the dynamic model of biopsy sampling behavior was established.The parameters of the dynamic model were determined by experimental research and parameter identification method.The influence of different tool speeds on the cutting force of soft tissue is given through experimental research.The higher the tool speed is,the smaller the cutting force required for cutting soft tissue is.With the in-vitro pig intestine as the experimental object,two effective biopsies of capsule endoscopy were successfully achieved,indicating the multiple biopsy capabilities of the capsule endoscopy.Secondly,the magnetic field distribution characteristics of permanent magnet are analyzed in order to researching the driving mechanism of active magnetic controlled capsule endoscopy.Based on the equivalent charge model,the magnetic field distribution model and the magnetic force field model of cylindrical permanent magnet are established.The accuracy of the proposed theoretical model is verified by simulation.By comparing the theoretical calculation results and simulation results,it is found that the accuracy of the model calculation can reach more than 95 %,which provides theoretical support for the precise driving and control of magnetic controlled capsule endoscopy.Finally,according to the biopsy requirements of lesions in different circumferential positions,a control strategy was proposed to realize the circumferential position and posture motion of the capsule endoscope in the intestine.The static model of the moving and rotating of the capsule endoscope was established,and the optimal solution with the minimum pressure on the intestine was determined by optimization method.An experimental platform for the motion of the capsule endoscope driven by an external magnet was built.The experimental results show that the capsule endoscope robot prototype can realize the backward motion driven by external magnetic field,and the stable motion conditions are given.The capsule endoscope circumferential attitude control and effective biopsy sampling operation are realized.