Biliary Stents with Integrated Magnetoelastic Resonant Sensors for Remote Monitor

University Of Michigan At Ann Arbor, Ann Arbor MI

Investigators

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Abstract

The goal of the proposed work is to enhance the options available for monitoring stent occlusion by developing and validating a wireless system which measures mass and viscosity changes caused by adherent occlusive material. The key component of this system is a magnetoelastic resonant sensor array integrated with the stent. The resonant response of the sensor array, which can be queried with external equipment, depends on the buildup of mass around the sensor. This proposal focuses on application of the system to biliary stents, which have performance requirements (including full scale range, resolution, and wireless range) that are important for other stent applications (including transjugular intrahepatic portosystemic shunts, coronary stents, and ureteral stents). When applied to biliary and other stent types, this system will aid physicians in avoiding unnecessary or delinquent interventions in the treatment of stent occlusion, resulting in increased efficiency and quality of care. The interdisciplinary project team includes investigators from engineering and gastroenterology with direct experience in device design, fabrication, and deployment, as well as diagnosis and treatment of relevant pathologies. Our preliminary work on this topic has allowed us to develop design and fabrication expertise and evaluate performance bounds of this technology. However, important questions remain about the applicability of the technology as a part of standard clinical use. Specifically, the performance of the sensor technology under dynamic biological loads, the biocompatibility of the implanted materials, and the deliverability and long-term stability of the device must be evaluated. The proposed effort seeks to investigate these questions and pursue suitable system performance. Important performance targets for the system include a full-scale range that includes a fully-occluded stent, a resolution of less than 1 mm of patent diameter, and a wireless range of at least 7.5 cm. The research is planned as a series of design, fabrication, and test iterations that will culminate in an in vivo feasibility study. The first task to be addressed is design and fabrication of a sensor array that will allow a full spatial mapping of occlusion in a biliary stent. This task will include material selection, predictive modeling, and process specification guided by our preliminary studies. Material selection will include initial biocompatibility testing to assess the use of magnetoelastic materials in a chronic implant. In vitro testing will be used to assist in providing a controllable assessment of the sensor performance in a biological environment. In situ testing in porcine carcasses will ensure that the array meets the basic requirements of surviving implantation and that the system can provide a usable signal in a clinical setting. An in vivo protocol will then be executed, consisting of month-long studies of the system in porcine specimens. This in vivo study will be structured to verify the usability and performance of the complete system.