ABSTRACT
The development of tomographic techniques for imaging the low-frequency (<2MHz), passive electromagnetic properties of materials non-invasively has been an active area of research since the 1980s. Most of this interest has been in the areas of medical imaging, where cross-sectional images 310of the human body are sought [ 138 , 479 ], and industrial imaging for the visualisation and control of processes in vessels and pipelines [ 1154 ]. Electrical imaging has also been used in environmental monitoring for tracking the migration of pollutants underground [ 222 ] and in archaeology for imaging submerged remains [ 784 ].
