Dielectric properties of human skin at an acupuncture point in the 50-75 GHz frequency range: a pilot study

The reason for using acupuncture points as exposure sites in some applications of millimeter wave therapy has been unclear. Acupuncture points have been suspected to exhibit particular direct current (DC), low-frequency electrical and optical properties compared to surrounding skin. To assess if such a biophysical correlation could exist at millimeter wave frequencies used in the therapy, we investigated the dielectric properties of an acupuncture point on the forearm skin within the 50-75 GHz range. These properties were compared with those of a neighboring ipsilateral control area and a corresponding contralateral control area. The complex reflection coefficient at the end of an open-ended rectangular waveguide loaded with a Teflon plug was measured with a vector network analyzer. A suitable model of the aperture admittance was used to calculate the dielectric properties of the skin at the measured spots. Statistical analyses were conducted with an ANOVA to compare the three sites. From these analyses, the dielectric properties of the acupuncture site were found to be somewhat different from those of surrounding non-acupuncture sites from 50 to about 61 GHz, in the case of the real part of the complex permittivity.