and Demosthenous, Andreas (2018) A high frame rate wearable EIT system using active electrode ASICs for lung respiration and heart rate monitoring. IEEE transactions on circuits and systems. I, Fundamental theory and applications, 65 (11). pp. 3810-3820.

A highly integrated, wearable electrical impedance tomography (EIT) belt for neonatal thorax vital multiple sign monitoring is presented. The belt has sixteen active electrodes. Each has an application specific integrated circuit (ASIC) connected to an electrode. The ASIC contains a fully differential current driver, a high-performance instrumentation amplifier (IA), a digital controller and multiplexors. The belt features a new active electrode architecture that allows programmable flexible electrode current drive and voltage sense patterns under simple digital control. It provides intimate connections to the electrodes for the current drive and to the IA for direct differential voltage measurement providing superior common-mode rejection ratio. The ASIC was designed in a CMOS 0.35-µm high-voltage technology. The high specification EIT belt has an image frame rate of 122 fps, a wide operating bandwidth of 1 MHz and multifrequency operation. It measures impedance with 98% accuracy and has less than 0.5 Ω and 1 o variation across all possible channels. The image results confirmed the advantage of the new active electrode architecture and the benefit of wideband, multifrequency EIT operation. The system successfully captured high quality lung respiration EIT images, breathing cycle and heart rate. It can also provide boundary shape information using an array of MEMS sensors interfaced to the ASICs.

This paper presents a human-machine interface that establishes a link between the user and a hand prosthesis. It successfully uses electrical impedance tomography, a conventional bio-impedance imaging technique, using an array of electrodes contained in a wristband on the user's forearm. Using a highperformance analog front-end application specific integrated circuit (ASIC) the user's forearm inner bio-impedance redistribution is accurately assessed. These bio-signatures are strongly related to hand motions and using artificial neural networks, they can be learned so as to recognize the user's intention in real-time for prosthesis operation. In this work, eleven hand motions are designed for prosthesis operation with a gesture switching enabled sub-grouping method. Experiments with five subjects show that the system can achieve 98.5% accuracy with a grouping of three gestures and an accuracy of 94.4% with two sets of five gestures. The ASIC comprises a current driver with common-mode reduction capability and a current feedback instrumentation amplifier (that occupy an area of 0.07 mm 2). The ASIC operates from ±1.65 V power supplies and has a minimum bio-impedance sensitivity of 12.7 mΩp-p.

This paper presents a passive phase-shift keying (PPSK) modulator for uplink data transmission for biomedical implants with simultaneous power and data transmission over a single 13.56 MHz inductive link. The PPSK modulator provides a data rate up to 1.35 Mbps with a modulation index between 3% and 38% for a variation of the coupling coefficient between 0.05 and 0.26. This modulation scheme is particularly suited for biomedical implants that have high power demand and low coupling coefficients. The PPSK modulator operates in conjunction with on-off-keying downlink communication. The same inductive link is used to provide up to 100 mW of power to a multi-channel stimulator. The majority of the system on the implant side was implemented as an application specific integrated circuit (ASIC), fabricated in 0.6- [Formula: see text] high voltage CMOS technology. The theory of PPSK modulation, simulated and measured performance evaluation, and comparison with other state-of-the-art impedance modulation techniques is presented. The measured bit error rate around critical coupling at 1.35 Mbps is below 6 ×10.

There has been considerable interest in electrical impedance tomography (EIT) to provide low-cost, radiation-free, real-time and wearable means for physiological status monitoring. To be competitive with other well-established imaging modalities, it is important to understand the requirements of the specific application and determine a suitable system design. This paper presents an overview of EIT circuits and systems including architectures, current drivers, analog front-end and demodulation circuits, with emphasis on integrated circuit implementations. Commonly used circuit topologies are detailed, and tradeoffs are discussed to aid in choosing an appropriate design based on the application and system priorities. The paper also describes a number of integrated EIT systems for biomedical applications, as well as discussing current challenges and possible future directions.

Eu3+‐activated borogermanate scintillating glasses with compositions of 25B2O3–40GeO2–25Gd2O3–(10−x)La2O3–xEu2O3 were prepared by melt‐quenching method. Their optical properties were studied by transmittance, photoluminescence, Fourier transform infrared (FTIR), Raman and X‐ray excited luminescence (XEL) spectra in detail. The results suggest that the role of Gd2O3 is of significance for designing dense glass. Furthermore, energy‐transfer efficiency from Gd3+ to Eu3+ ions can be near 100% when the content of Eu2O3 exceeds x = 4, the corresponding critical distance for Gd3+–Eu3+ ion pairs is estimated to be 4.57 Å. The strongest emission intensities of Eu3+ ions under both 276 and 394 nm excitation are simultaneously at the content of 8 mol% Eu2O3. The degree of Eu–O covalency and the local environment of Eu3+ ions are evaluated by the value of Ωt parameters from Judd–Ofelt analysis. The calculated results imply that the covalency of Eu–O bond increases with the increasing concentration of Eu3+ ions in the investigated borogermanate glass. As a potential scintillating application, the strongest XEL intensity under X‐ray excitation is found to be in the case of 6 mol% Eu2O3, which is slightly different from the photoluminescence results. The possible reason may be attributed to the discrepancy of the excitation mechanism between the ultraviolet and X‐ray energy.

This paper presents a multichannel stimulator ASIC for an implantable vestibular prosthesis. The system features versatile stimulation management which allows fine setting of the parameters for biphasic stimulation pulses. To address the problem of charge imbalance due to rounding errors, the digital processor can calculate and provide accurate charge correction. A technique to reduce the data rate to the stimulator is described. The stimulator ASIC was implemented in 0.6-μ m high-voltage CMOS technology occupying an area of 2.27 mm(2). The measured performance of the ASIC has been verified using vestibular electrodes in saline.

This paper presents a high accuracy hand gesture recognition system based on electrical impedance tomography (EIT). The system interfaces the forearm using a wrist wrap with embedded electrodes. It measures the inner conductivity distributions caused by bone and muscle movement of the forearm in real-time and passes the data to a deep learning neural network for gesture recognition. The system has an EIT bandwidth of 500 kHz and a measured sensitivity in excess of 6.4 Ω per frame. Nineteen hand gestures are designed for recognition, and with the proposed round robin sub-grouping method, an accuracy of over 98% is achieved. I.