Suppression of Heat Generation in Magnetic Stimulation Coil Applied for Treating Dysphagia

The authors are developing magnetic stimulation coils for use in the treatment of dysphagia. The prototype coil manufactured in our previous research can induce large contraction of the suprahyoid muscles, which should be trained for normal swallowing. In this study, the heat generation in the coil during magnetic stimulation is investigated and suppressed. A numerical analysis showed that the main cause of the generated heat is the eddy current in the coil conductor induced by magnetic flux from the tip of the magnetic core. The analysis also showed that a parallel coil with a cross connection has an ideal current distribution in the coil conductor and thus best suppresses heat generation during magnetic stimulation. The heat-suppressing coil has parallel divided coil conductors and an appropriate connection between the conductors to level the current in each conductor. Moreover, measurements of the temperature rise in prototype coils during magnetic stimulation confirm that heat generation can be greatly suppressed by dividing the conductor and using an appropriate connection between the divided conductors.