Sensor for Measuring the Contact Force From Human Myenteric Contractions for In Vivo Robotic Capsule Endoscope Mobility

摘要

Multiple research groups are investigating the feasibility of miniature, in vivo, untethered robots that are capable of traversing the gastrointestinal (GI) tract for the purpose of diagnosing pathologies, acquiring biometrics, and performing next-generation minimally invasive surgical procedures [1]. This effort has been hindered by the lack of knowledge concerning the biomechanical properties of the intraluminal environment and in particular, the lack of understanding of the active, live response of bowel tissue to so-called Robotic Capsule Endoscopes (RCEs). To the authors' knowledge, current research of the contact force exerted by the bowel tissue on an RCE has focused exclusively on in vitro testing of excised tissue. To create a unified model of the intraluminal environment, however, greater understanding of the tissue's active response is needed and to this end, the authors have established a comprehensive program for characterizing this as well as other in vivo forces [2-5]. This work could lead to effective RCE technologies whose candidate procedures are numerous. For example, gallstone and polyp removal, biopsy acquisition, identification and repair of ulcers, and radiopaque marking may all be possible with the RCE platform. Current research in this area is growing, with various groups developing RCEs [6,7], but development is hindered by the lack of biomechanical data.The forces experienced by an RCE are generated from a variety of sources. This project focuses on the development of a human-compatible version of a sensor and support system developed in previous work that measures the myenteric contractions of small bowel tissue on an RCE-sized solid bolus [2]. The system is called the Migrating motor complex Force Sensor (MFS) and consists of a temperature sensor, monometer, and a series of four torus-shaped balloons that expand to the nominal inner diameter of the intestine and sense contact force (Fig. 1). The sensor is implanted through incisions in the abdominal wall and lumen of the small intestine, where it measures intraluminal pressure as well as the contact force generated by the bowel wall. Theory of operation, accuracy, and other details our presented in previous works in which MFSs were characterized [2] and surgically implanted in multiple pigs in the proximal, middle, or distal regions of the small intestine to measure contact force [3].The purpose of the research presented here is to develop a new version of the MFS to be used in human test subjects. Specifically, the objectives are to: a) redesign the MFS so all materials in contact with human tissue are biocompatible; b) develop an implantation procedure that is minimally invasive and meets surgery time constraints; c) validate the functionality of the human MFS and revised implantation procedures through in vitro and in vivo testing on live porcine models; and d) receive regulatory approval for testing on humans in an operating room setting.The following steps were taken to accomplish the above objectives. To eliminate the risk of a human allergic reaction, device materials were reconfigured to be implant biocompatible for up to one month, even though total implantation time is less than 10 minutes. The latex sensing surfaces were replaced with custom-made silicone parts (MED-2014, nuSil, LLC), which was easily accomplished by reusing the custom aluminum forms (used for latex balloon manufacturing) with the manufacturer-suggested silicone curing process. The steel hubs were remade using 316LVM stainless “surgical” steel; polytetrafluoroethylene tubing remained the same, as did internal components which do not contact the tissue.Standard laparoscopic techniques were used to minimize the invasiveness and expedite surgery time (<10 min) required for implanting the sensor, gathering data, and removal. Instead of open surgery, as was done in the porcine study [3], three 10 mm trocars were used for a laparoscope, grasper, and sensor insertion, respectiv