Measurement of the optical properties of in-vitro organ-surface bonghan corpuscles of rats

The meridian is essential in traditional oriental medicine and gets increasingly important for photo- treatment with laser stimulation at the acupuncture point. In this article, firstly, the optical properties of a Bonghan corpuscle in meridian-like tissue on the organ surface of a rat were studied, then, they were compared with those in the surrounding tissue - dermis and muscles. Secondly, the origin of the optical properties was studied from the viewpoint of the histological microstructure of the organ-surface Bonghan corpuscle by using transmission electron microscopy. In our study, an optical-fiber-based system was employed and calibrated with a tissue-like solution. The transmittance and the reflectance of an organ-surface Bonghan corpuscle in a meridian-like tissue, dermis, and muscle were separately measured in the range of 400 - 700 nm in wavelength. Then, they were corrected with a Monte Carlo simulation, and the optical properties were obtained using an inverse adding-doubling method. The results demonstrated that the organ-surface Bonghan corpuscle had lower absorption and scattering coefficients than its surrounding tissue, dermis and muscles, which made the organ-surface Bonghan corpuscle appear more transparent. The organ-surface Bonghan corpuscle can transport light with a high efficiency and can act as a light channel for laser treatment at acupuncture points of humans. The color of the organ surface Bonghan corpuscle is determined by both the intensity of the light reflected from the corpuscle and the sensitivity of the eye to different light wavelengths, so it appears yellowish. The transmission electron micrographs showed that the concentration of collagen fiber in organ-surface Bonghan corpuscle was much lower than it was in surrounding tissue, dermis and muscles, which explains the much smaller scattering of a Bonghan corpuscle in comparison with that of the dermis and muscles.