ACT3 - A HIGH-SPEED, HIGH-PRECISION ELECTRICAL-IMPEDANCE TOMOGRAPH

This paper presents the design, implementation, and performance of Ren sselaer's third-generation Adaptive Current Tomograph, ACT3. This syst em uses 32 current sources and 32 phase-sensitive voltmeters to make a 32-electrode system that is capable of applying arbitrary spatial pat terns of current. The instrumentation provides 16 b precision on both the current values and the real and reactive voltage readings and can collect the data for a single image in 133 ms. Additionally, the instr ument is able to automatically calibrate its voltmeters and current so urces and adjust the current source output impedance under computer co ntrol. The major system components are discussed in detail and perform ance results are given. Images obtained using stationary agar targets and a moving pendulum in a phantom as well as in vivo resistivity prof iles showing human respiration are shown.