Background High-resolution (HR) extracellular mapping allows accurate profiling of normal and dysrhythmic slow wave patterns. A current limitation is that cables traverse the abdominal wall or a natural orifice, risking discomfort, dislodgement or infection. Wireless approaches offer advantages, but a multi-channel system is required, capable of recording slow waves and mapping propagation with high fidelity. Methods A novel multi-channel (n=7) wireless mapping system was developed and compared to a wired commercial system. Slow wave signals were recorded from the porcine gastric and intestinal serosa in-vivo. Signals were simultaneously acquired using both systems, and were filtered and processed to map activation wavefronts. For validation, the frequency and amplitude of detected events were compared, together with the speed and direction of mapped wavefronts. Key Results The wireless device achieved comparable signal quality to the reference device, and slow wave frequencies were identical. Amplitudes of the acquired gastric and intestinal slow wave signals were consistent between the devices. During normal propagation, spatiotemporal mapping remained accurate in the wireless system, however, during ectopic dysrhythmic pacemaking, the lower sampling resolution of the wireless device led to reduced accuracy in spatiotemporal mapping. Conclusions and Inferences A novel multichannel wireless device is presented for mapping slow wave activity. The device achieved high quality signals, and has the potential to facilitate chronic monitoring studies and clinical translation of spatiotemporal mapping. The current implementation may be applied to detect normal patterns and dysrhythmia onset, but HR mapping with finely spaced arrays currently remains necessary to accurately define dysrhythmic patterns.
Magnetic localization has been used in a variety of applications, including the medical field. Small magnetic tracers are often modeled as dipoles and localization has been achieved by solving well-defined dipole equations. However, in practice, the precise calculation of the tracer location not only depends on solving the highly nonlinear dipole equations through numerical algorithms but also on the precision of the magnetic sensor, accuracy of the tracer magnetization, and the earth magnetic field (EMF) measurements. We have developed and implemented a comprehensive calibration method that addresses all of the aforementioned factors. We evaluated this method in a bench-top setting by moving the tracer along controlled trajectories. We also conducted several experiments to track the tongue movement in a human subject.
Stomach contractions are initiated and coordinated by an underlying electrical activity (slow waves), and electrical dysrhythmias accompany motility diseases. Electrical recordings taken directly from the stomach provide the most valuable data, but face technical constraints. Serosal or mucosal electrodes have cables that traverse the abdominal wall, or a natural orifice, causing discomfort and possible infection, and restricting mobility. These problems motivated the development of a wireless system. The bidirectional telemetric system constitutes a front-end transponder, a back-end receiver and a graphical user interface. The front-end module conditions the analog signals, then digitizes and loads the data into a radio for transmission. Data receipt at the back-end is acknowledged via a transceiver function. The system was validated in a bench-top study, then validated in-vivo using serosal electrodes connected simultaneously to a commercial wired system. The front-end module was 35×35×27 mm3 and weighed 20 g. Bench-top tests demonstrated reliable communication within a distance range of 30 m, power consumption of 13.5 mW, and 124-hour operation when utilizing a 560-mAh, 3-V battery. In-vivo, slow wave frequencies were recorded identically with the wireless and wired reference systems (2.4 cycles/min), automated activation time detection was modestly better for the wireless system (5% vs 14% false positive rate), and signal amplitudes were modestly higher via the wireless system (462 vs 386 μV; p<0.001). This telemetric system for slow wave acquisition is reliable, power efficient, readily portable and potentially implantable. The device will enable chronic monitoring and evaluation of slow wave patterns in animals and patients.
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