Electrical Impedance Tomography for Biomedical Applications: Circuits and Systems Review

Abstract

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.

Analysis, Simulation, and Development of a Low-Cost Fully Active-Electrode Bioimpedance Measurement Module

“…This actually could lead the Opamps to saturate and as a consequence, the output current to clip. To avoid this effect in mirrored topologies, Common-Mode feedback configurations have been proposed [7,26]. Nonetheless, this requires additive active components, which is impractical in the case of a fully-active electrode discrete-element configuration.…”

“…Such bio-markers include heart rate (HR), respiration rate (RR), blood pressure (BP), pulse transit time (PPT), and blood glucose levels. These can be acquired either by simple bioimpedance measurement patterns, such as bipolar or tetrapolar measurement, or more complex measurement techniques, such as Electrical Impedance Tomography (EIT) or Electrical Impedance Spectroscopy (EIS) [7,8]. The latter are also very useful for monitoring time or frequency dependent conditions, such as real-time ventilation, brain hemorrhage, or malignant tumors.…”

“…The latter are also very useful for monitoring time or frequency dependent conditions, such as real-time ventilation, brain hemorrhage, or malignant tumors. Furthermore, bioimpedance measurement techniques are safe, radiation-free, and low-cost [7]. In most cases, they are also non-invasive, making the measurement process much simpler [7].…”

“…Furthermore, bioimpedance measurement techniques are safe, radiation-free, and low-cost [7]. In most cases, they are also non-invasive, making the measurement process much simpler [7].…”

“…Such topologies include the well-known Howland current pump (HCP) [14][15][16][17][18][19], the Tietze topology [20], the load-in-the-loop topology [21], and differential-difference topologies [22][23][24]. Current-mode approach makes use of operational transconductance amplifiers (OTAs) [7,11,25,26] or current conveyors (CCII) [15,27,28] for the current excitation. In all cases, the load driven by the output current can be either grounded or floating.…”