Optic Visualization of Auricular Nerves and Blood Vessels: Optimisation and Validation

Auricular blood vessels can be visualized by transillumination of the auricular tissue. The optimisation and validation of the optic visualization are the main subject of this work. Since blood vessels and nerve fibers can be found along one another, the transillumination reveals locations of auricular nerves to unaided human eye. The visualization of the nerves is needed by physicians to precisely insert needles into the auricle for electrical stimulation of auricular nerves. The stimulation is applied to relieve chronic pain and normalize vital physiological parameters. Theoretical approaches are shortly considered which are related to light absorption coefficients of different auricular tissue types and coefficient changes over wavelength. The theory predicts optimal optical contrasts if green and blue colors of light are applied. An experimental validation has been carried out using a novel transillumination device, a finger thimble, among young and elderly, male and female; in total 22 volunteers. Complementary experimental approaches have confirmed theoretical reasoning and have been used to optimize the optical contrast and applied color mixture even further.