Transmission of phototherapy through human skin: dosimetry adjustment for effects of skin color, body composition, wavelength and light coupling to skin

摘要

Purpose: To examine factors that affect penetration of phototherapy. Methods: Age, sex, height, and weight were recorded; skin color, skinfold thickness, and light transmission through a skinfold were measured over biceps and triceps muscles, and at the anterior waistline. Light was generated using two 23-diode LED arrays at 840 nm and 660 nm with surface area of 7 cm~2. Photon irradiation was measured using an Optical Power Meter consisting of a 1x1-cm~2 light detector placed in the centre of the illuminated 7 cm~2 spot. Transmission was measured using three skin-diode coupling conditions. Results: Penetration of LED irradiation increased when diodes were coupled to skin with pressure. Red light attenuated more rapidly than infrared light and the attenuation of red light increased as skin color darkened. Penetration of red and infrared light decreased as the amount of subcutaneous fat increased. There were gender effects on penetration of infrared light at normal and low BMI values. Conclusions: When using divergent light sources for phototherapy, radiant exposure should take into account individual physical characteristics, irradiation wavelength and diode configuration of the laser therapy system.