Han-Ping Hung, Ping-Yen Hsieh, Ying-Hung Chen, Eric Kuo-Hao Tang, Sheng-Nan Tsai, Ju-Liang He, Feng Chia University, Taiwan
Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive medical device that uses an electromagnetic coil powered by a high pulse voltage and high electric pulse current to generate a strong instantaneous magnetic field for stimulating nerve cells in the brain, thereby treating neurological disorders. This therapy has shown diagnostic and therapeutic potential in the central nervous system with a wide variety of disease related to neurology and mental health, such as depression and Alzheimer's disease. To withstand sufficiently high power, the rTMS copper coil suffers bulky and heavy feature; additionally, the water cooling is indispensable for reducing coil temperature under extreme output power. To fulfill the unmet need for localized treatment and portability, this study aims to develop the miniaturized rTMS coil while withstanding high power, which is supplied by a silicon-controlled rectifier (SCR) power generator. To resolve heat dissipation issue, an air-cooling method is proposed involving the utilization of thermoelectric modules and air pump to deliver cool air to the coil. After repeated computer simulation and experimental procedure to optimize the airflow distribution and maximize the cooling performance. The results show that under condition of a peak voltage of 440 V and peak current of 1800 A (a pulse duration of 300 μs at a pulse frequency of 10 Hz), a magnetic flux density of 1.39 T is obtained for the miniaturized rTMS coil with a diameter of 6 cm. After continuous operation for 30 min, the coil temperature is increased by only 9 ℃. These promising results demonstrated that the performance of the miniaturized rTMS coil is comparable to many commercial products, which can meet the targeted treatment of specific areas and growing needs of home/community medical services.