Magnetohydrodynamic Approach to Effective Blood-Flow Con-trol Utilizing ELF fields

To describe the broad potential opportunities in magnetohydrodynamic (MHD) studies for magnetic therapies, we examined the MHD effects of extremely low frequency (ELF) magnetic fields produced by a prototype diverted from an existing alternating magnetic therapy apparatus (AMTA), employing functional near-infrared spectroscopic (fNIRS) analyses. Experimental Five healthy male subjects ranging in age from 33 to 68 (two subjects each in their 30 s and 40 s, and one subject in his 60 s) took part in this experiment. For ELF stimulations to the subjects, we used a prototype equipped with two additional coils for twisting the ELF field of a commercial AMTA (NIKKEN, Biobeam 21). The flux-density $( B_{eff})$ distribution from the AMTA is shown in Fig. 1. The maximum density was revealed as 60 mT at each center of the internal iron core. We were able to obtain the $B_{eff}$ of 60 mT on the coil surface, under a constant current of 0.34 A. Then the field frequencies of all the coils were fixed at 50 Hz, and the sinusoidal waveform signals from the additional coils were synchronized in phase in accordance with the axis of a part of the human body. All measurements on fNIRS (Hitach HOT121B) were carried out while the subjects were sitting on a chair in a quiet room at a temperature of $23 ^{\circ}\mathrm {C}$ and humidity of 50%. Discussion Our experimental results showed the fact that the proper twisted ELF fields induced from the prototyped machine were able to control the autonomic nervous system, depending on the field strength. We therefore estimated that the mechanism of blood-flow accelerations induced by ELF stimulations is due to a little temperature increase generated by an induced eddy current, and the following joule-heat gradient of the current. Consequently, the blood flow is probably accelerated in the process of human bioactivity via the autonomic nervous system [1–4], in order to reduce the induced fever and/or the heat gradient. On the other hand, there were no significant differences across the two mounting positions (Fig. 2A and 2B) in the behaviors of arterial/venous blood flows. It is quite probable that the arterial blood flows (Fig. 2A) could not generate an eddy current necessary for activations of the autonomic nervous system, although the flows grasping as a pulsating flow might induce an electromagnetic induction phenomenon in a fluid. We firmly believe that MHD effects for a virtual magnetic therapy are induced by moderately swept turbulence in the blood.