Changes of Soft-Tissue Water Examined With Magnetic Resonance and Electrical Impedance Tomography: An in Vivo Experiment

Abstract

The purpose of this study was the examination of short-term changes in soft- tissue water under in vivo conditions. In 12 healthy volunteers the water distri bution of a selected slice of the lower limb was examined after change of position and rapid infusion of 0.9% saline solution. Two methods were used for data acquisition: magnetic resonance imaging (MRI) (Repetition Time (TR) = 1600 msec, Inverstion Time (TI) = 300 msec, Echo Time (TE) = 22 msec) and electrical impedance tomography (EIT). In orthostatic equilibrium all 12 volunteers dem onstrated changes of MR signal intensity and resistivity in the range of 12% and 7%, respectively. After infusion, mean changes of signal intensity and resistivity were 7% and 4%, respectively. The overall correlation of MRI and EIT was —0.96 (p < 0.001). Results indicate that inversion recovery sequences are a sen sitive method of detecting in vivo changes of water distribution in selected areas of the body.