Peripheral nerve magnetic stimulation: influence of tissue non-homogeneity.

Background: Peripheral nerves are situated in a highly non-homogeneous environment, including muscles, bones, blood vessels, etc. Time-varying magnetic field stimulation of the median and ulnar nerves in the carpal region is studied, with special consideration of the influence of non-homogeneities.

Methods: A detailed three-dimensional finite element model (FEM) of the anatomy of the wrist region was built to assess the induced currents distribution by external magnetic stimulation.

Estimation of current density distribution under electrodes for external defibrillation.

Background: Transthoracic defibrillation is the most common life-saving technique for the restoration of the heart rhythm of cardiac arrest victims. The procedure requires adequate application of large electrodes on the patient chest, to ensure low-resistance electrical contact. The current density distribution under the electrodes is non-uniform, leading to muscle contraction and pain, or risks of burning.

Magnetic stimulation for non-homogeneous biological structures.

Background: Magnetic stimulation has gained relatively wide application in studying nervous system structures. This technology has the advantage of reduced excitation of sensory nerve endings, and hence results in quasi-painless action. It has become clinically accepted modality for brain stimulation.

Effect of contour shape of nervous system electromagnetic stimulation coils on the induced electrical field distribution.

Background: Electromagnetic stimulation of the nervous system has the advantage of reduced discomfort in activating nerves. For brain structures stimulation, it has become a clinically accepted modality. Coil designs usually consider factors such as optimization of induced power, focussing, field shape etc.

Electrical current distribution under transthoracic defibrillation and pacing electrodes.

The known effect of high current density under the perimeter of defibrillation electrodes, leading to skin damage and even severe burns in some cases, has been considered by many investigators. Two main approaches for improvement were proposed: (i) interfacing with layers of varying and high resistivity and (ii) lengthening and shaping the perimeter line. Using finite element and physical modelling, it is shown that the second approach does not yield significant improvement in the distribution uniformity.

Optimization of the defibrillation current density in the heart region by a two-layer segmented electrode.

Transthoracic defibrillation is a procedure applying high intensity electrical current through the thorax region by electrodes, in order to simultaneously activate most of the myocardial cells, thus enforcing them to reinstate a normal rhythm. A solution is proposed for analysis and synthesis of the current density distribution field in the heart region. In an attempt to reach uniform excitation of the greatest possible quantity of myocardial cells, a field image is searched for, with the J-vector uniformity distribution as a criterion.