Impedance magnetic resonance imaging: A method for imaging of impedance distributions based on magnetic resonance imaging

Magnetic resonance imaging (MRI) techniques have become important tools in medicine and biology. Conventional MRI, however, produces no information about the electrical properties of the body. This article proposes a new and noninvasive method for imaging electrical properties such as conductivity and impedance based on MRI techniques. The basic idea is to use the shielding effects of induced eddy currents in the body on spin precession. Two types of methods are introduced; (i) a large flip angle method, and (ii) a third coil method. The large hip angle method enhances the shielding effects of conducting tissues at the given Larmor frequency. The third coil method detects the shielding effects of conducting tissues at an arbitrary frequency. Both phantom and animal experiments have been carried out to verify this concept using a MRI system of 7.05 T with a bore size of 183 mm in diameter. (C) 1998 American Institute of Physics. [S0021-8979(98)23711-X].