XIX Sympozjum Srodowiskowe PTZE - materialy.pdf

Optimal design environment
XIX Sympozjum PTZE, Worliny 2009
To design the stimulating coils we have constructed a distributed optimization environment. It
uses hybrid local area network resources to solve computationally expensive inverse problems
of bioelectromagnetism. Built on the basis of the mature, sophisticated research environment
ECJ, our system contains the whole functionality of it, especially the rich, universal set of
optimization algorithm: genetic algorithms, evolutionary strategies, multiobjective optimization,
particle swarm optimization and many others. Our main focus was to adapt ECJ for
computationally challenging field problems, which are usually implemented in other, than
Java, programming languages. In most of our applications Java RMI is used as a bridge between
ECJ and our C++ field simulators, running in parallel on many computers simultaneously.
Results
Three possible geometries of the stimulating coil have been tested: single solenoid, figure-ofeight
coil, and a pair of solenoids. All coils were fed with current density 367.5 A/mm 2 corresponding
to currents up to 4000 A depending on the construction details. The figure-ofeight
coil was able to generate the highest value of the stimulating field, but the obtained result
was at the level of fT/2. These values are too small to stimulate the nerve, but more sophisticated
cooling systems and eventually better (long lasting) stimulus can allow successful
magnetic stimulation.
It has been shown, that the use of electric scalar potential in hybrid FEM-integral model allows
the computationally effective simulation of such phenomena and may be use for optimal
design of the stimulator. Magnetic stimulation of the vagus nerve is extremely difficult, but
worth of further investigations.
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