Medical applications for implantable devices utilizing electromagnetic near fields

Hidetoshi Matsuki
Professor
Department of Electrical and Communication Engineering, Graduate School of Engineering

We are examining the in vivo application of electromagnetic fields with regard to biomagnetism and energy management. With recent social changes, it is important to improve the environment as well as medical and other equipment systems. Most medical equipment is electrical and indispensable to health care and general health. It is not an overstatement to say that electrical equipment affects the human life span. Medical equipment ranges from large devices used in large hospitals, to portable or internal devices for personal use. From the perspective of electrical engineering, the power source of equipment is an important issue for the majority of medical devices. Power savings (i.e., low power consumption) and the use of wireless equipment hold the key to promoting the widespread use of medical equipment in a variety or areas, including social welfare and nursing. The next generation of electrical equipment should not need to be connected directly to a power source. Contactless power transfer will benefit medical equipment. When such equipment can be mounted to a device with no internal energy source, a dramatic improvement of the health system is envisioned. We expect such equipment to contribute greatly to medical treatment in the 21^stCentury. Medical equipment that constitutes a fully self-contained system with non-contact energy transmission includes the following:

Type A: Uses transferred energy to power implanted devices, such as artificial hearts and micromachines;

Type B: Uses electrical power, such as in pacemakers; and

Type C: Uses a heat source, such as in devices that produce local hyperthermia.

These products are assumed to be fully self-contained and the technology is based on the provision of non-contact energy transfer. To transmit energy without contact, it is thought best to utilize electromagnetic fields in order to achieve high energy density and efficiency. Currently, we are developing a long-lasting energy supply system for a functional hyperthermia system and for self-contained medical equipment. The functional hyperthermia system causes the local necrosis of tumors by exciting an implanted magnet, using a temperature-control mechanism located outside the body. Since there is no need to measure the temperature of the internal component, there are expectations that this technology will lead to great advances in medicine. We have also obtained excellent results in developing an energy supply system for a fully self-contained artificial heart, which has been developed by this institute; the efficiency of the transmission transformer is the highest that has been achieved, as yet, worldwide. The original structure, which has great mechanical flexibility, while being only a few millimeters thick, has attracted much attention. The accompanying systems for monitoring the artificial heart and controlling energy transmission, both of which involve a non-contact signal, have a unique integrated energy control system. Once electrical power can be transferred freely in a contactless manner, what kind of world will await us? In developing this electrical transmission technology, we are also studying power transmission to ordinary electrical equipment and non-contact supply to nursing care robots. Furthermore, to develop an electrical transmission system that can be used in extreme conditions, such as undersea and in deep space, we are conducting research on the "Cordless Power Station". Originally the term "barrier free" meant eliminating physical differences, but it has come to include the meaning of "removing mental and social barriers". To this term, we would like to add the definition of "a world where no power cords exist". However, since these technologies are based on the use of electromagnetic fields, the biological effects of electromagnetic fields on the human body and health should also be studied. With this in mind, we have started studying the effects of magnetic fields in vivo .

A hybrid implant-type hyperthermia heating element. The heating element is connected to a magnetic micromachine. The red area is the actual heating area (joint study with the Research Institute of Electrical Communication, Arai Laboratory.)