Electrical impedance tomography SoC and system for 3D lung ventilation monitoring

Abstract

The wearable 3D lung ventilation monitoring system is proposed with electrical impedance tomography (EIT). It consists of two types of SoCs, active electrode (AE)-SoC and Hub-SoC, mounted on wearable belts. The 48-channel AE-SoCs are integrated on flexible printed circuit board (FPCB) belt, and Hub-SoC is inte-grated in the hub module which performs data gathering and wireless communication between an external imaging device. To get high accuracy under variation of conductivity, the dual-mode current stimulator pro-vides the optimal frequency for TD(time difference)-EIT and FD(frequency difference)-EIT with simultane-ous 4k ~ 128kHz impedance sensing. A wide dynamic range instruments amplifier is proposed to provide 94dB of wide dynamic range impedance sensing. In addition, 48-channel AE system with the dedicated communication and calibration is implemented to achieve $1.4m\omega$ sensitivity of impedance difference in in-vivo environment. The AE-/Hub-SoCs occupy $3.2mm^2$ and $1.3mm^2$ in 65nm CMOS technology and con-sume $124\muW$ and 1.1mW with 1.2V supply, respectively. The proposed system integrates a belt board and the hub board in a waist support type clothes for the user's comfort and convenience. After the measured impedance data is transferred to hub-SoC in the Hub board, it is preprocessed and transferred to an external imaging device using Bluetooth module. As a result, the proposed system can display EIT images which are reconstructed with 90% of accuracy and 10 frames/s of real-time 3D lung images. It has only 357g weight and operates at least 6 hours with 3.7V 200mAh battery.