Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine, Charles University;
Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine, Charles University.
J Vis Exp. 2021 Aug 27(174). doi: 10.3791/62864.
Ambulatory pH monitoring of pathological reflux is an opportunity to observe the relationship between symptoms and exposure of the esophagus to acidic or non-acidic refluxate. This paper describes a method for the development, manufacturing, and implantation of a miniature wireless-enabled pH sensor. The sensor is designed to be implanted endoscopically with a single hemostatic clip. A fully passive rectenna-based receiver based on a zero-bias Schottky diode is also constructed and tested. To construct the device, a two-layer printed circuit board and off-the-shelf components were used. A miniature microcontroller with integrated analog peripherals is used as an analog front end for the ion-sensitive field-effect transistor (ISFET) sensor and to generate a digital signal which is transmitted with an amplitude shift keying transmitter chip. The device is powered by two primary alkaline cells. The implantable device has a total volume of 0.6 cm and a weight of 1.2 grams, and its performance was verified in an ex vivo model (porcine esophagus and stomach). Next, a small footprint passive rectenna-based receiver which can be easily integrated either into an external receiver or the implantable neurostimulator, was constructed and proven to receive the RF signal from the implant when in proximity (20 cm) to it. The small size of the sensor provides continuous pH monitoring with minimal obstruction of the esophagus. The sensor could be used in routine clinical practice for 24/96 h esophageal pH monitoring without the need to insert a nasal catheter. The "zero-power" nature of the receiver also enables the use of the sensor for automatic in-vivo calibration of miniature lower esophageal sphincter neurostimulation devices. An active sensor-based control enables the development of advanced algorithms to minimize the used energy to achieve a desirable clinical outcome. One of the examples of such an algorithm would be a closed-loop system for on-demand neurostimulation therapy of gastroesophageal reflux disease (GERD).
病态反流的动态 pH 监测有机会观察到症状与食管酸性或非酸性反流物暴露之间的关系。本文介绍了一种微型无线 pH 传感器的开发、制造和植入方法。该传感器设计为通过单个止血夹进行内镜植入。还构建并测试了一种基于零偏置肖特基二极管的完全无源整流天线接收器。为了构建该设备，使用了两层印刷电路板和现成的组件。带有集成模拟外设的微型微控制器用作离子敏场效应晶体管 (ISFET) 传感器的模拟前端，并生成数字信号，该数字信号通过移频键控发射芯片传输。该设备由两节碱性电池供电。植入式设备的总体积为 0.6 立方厘米，重量为 1.2 克，其性能已在离体模型（猪食管和胃）中得到验证。接下来，构建了一种小型足迹无源整流天线接收器，可以轻松集成到外部接收器或植入式神经刺激器中，并证明当它靠近（20 厘米）植入物时可以接收来自植入物的射频信号。传感器的小尺寸提供了最小程度的食管阻塞的连续 pH 监测。该传感器可用于常规临床实践中 24/96 小时食管 pH 监测，而无需插入鼻导管。接收器的“零功率”特性还可用于自动进行微型下食管括约肌神经刺激器的体内校准。基于传感器的主动控制可以开发先进的算法，以最小化所需能量来实现理想的临床效果。这种算法的一个示例是用于治疗胃食管反流病 (GERD) 的按需神经刺激治疗的闭环系统。
