Magnetic resonance imaging of alternating electric currents

Electric Current Density Imaging (CDI) is a new modality of magnetic resona nce imaging that enables electric current distribution imaging in conductiv e samples containing water. So far, two CDI techniques have been in use: DC -CDI operating at zero frequency and RF-CDI operating at the RF Larmor freq uency. In this paper we present a new CDI technique. which extends the CDI frequency range to alternating electric currents (AC-CDI). First, a theoret ical model for the electric current response to the alternating voltage is presented. Later, this model is used for the frequency analysis of the AC-C DI sequence. Additionally, the effect of off-resonance spins and imperfect refocusing RF pulses on the stability of the AC-CDI sequence and the echo f ormation is studied. The new theory is verified by experiments on a model s ystem and compared to the other two methods: DC-CDI and RF-CDI. Finally, an application of the AC-CDI sequence to biological systems is demonstrated b y an experiment on a wood twig in which an increase of approximately 30% wa s obtained at AC as compared to DC electric current. (C) 2001 Elsevier Scie nce Inc. All rights reserved.