%0 Journal Article
%T Safety assessment of near infrared light emitting diodes for diffuse optical measurements
%A Alper Bozkurt
%A Banu Onaral
%J BioMedical Engineering OnLine
%D 2004
%I BioMed Central
%R 10.1186/1475-925x-3-9
%X Temperature increase of the human skin caused by near infrared LED has been measured by means of in-vivo and in-vitro experiments. Effects of the conducted and radiated heat in the temperature increase have been analyzed separately.Elevations in skin temperature up to 10¡ãC have been observed. The effect of radiated heat due to NIR absorption is low ¨C less than 0.5¡ãC ¨C since emitted light power is comparable to the NIR part of sunlight. The conducted heat due to semiconductor junction of the LED can cause temperature increases up to 9¡ãC. It has been shown that adjusting operational parameters by amplitude modulating or time multiplexing the LED decreases the temperature increase of the skin significantly.In this study, we demonstrate that the major risk source of the LED in direct contact with skin is the conducted heat of the LED semiconductor junction, which may cause serious skin burns. Adjusting operational parameters by amplitude modulating or time multiplexing the LED can keep the LED within safe temperature ranges.New medical applications using optical measurement techniques are emerging rapidly. These methods are used to study the content of biological pigments and tissue structures by analyzing the absorption and scattering of the induced light. When visible or near infrared light at specific wavelengths in the window of 600 to 950 nm (fig. 1) is shone through the tissue, information about the amount of blood chromophores such as oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) can be obtained. This constitutes an important measure of the hemodynamic state of the tissue [1], and is the principle upon which pulse oximetry is based.The hazard potential of the near-infrared light should be considered from two perspectives: eye hazards and skin hazards. The effect of NIR light on eye and skin are studied separately since the eye lens focuses the light on the retina. Focused light is stronger in terms of irradiance than non-focused light. Hence, injury potential inc
%U http://www.biomedical-engineering-online.com/content/3/1/9