Transcranial Yellow, Red, and Infrared Laser and LED Stimulation: Changes of Vascular Parameters in a Chick Embryo Model

Background: The use of transcranial laser or light-emitting diode (LED) therapy in the treatment of different neurological diseases is attracting increasing attention. The main goal of this study was to investigate different kinds of scientifically and commercially available laser (yellow, red, and infrared) and LED stimulation systems for the first time using a chick embryo model under a fixed human cadaver (scalp and/or skull) and without this anatomical preparation. Methods: In the present study, the extra-embryonic vasculature of a 1-week-old chick embryo chorioallantoic membrane (CAM) was investigated. For stimulation, four different systems were used (infrared LED and yellow, red, and infrared laser). Four measurement periods were compared: before stimulation, immediately after stimulation onset, immediately after the 10-min stimulation was turned off, and 6 min after stimulation had ended. Special image processing programs developed at the Beijing University of Science and Technology were used for data analysis. Results: The different kinds of laser induced different effects, e.g. the direct stimulation with yellow laser led to initial vasoconstriction (–17%), whereas yellow