The effect of device position and use of transparent covers on the irradiance distribution of LED phototherapy devices

Master Thesis


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Background Effective phototherapy reduces neonatal jaundice and its complications. Irradiance increases as the distance of the light source decreases from a single phototherapy light. There are limited studies of the effect of distance and positional changes on different LED light designs on achieving effective phototherapy. Objectives To describe and compare the effect of distance, angle and plastic barriers on three different LED lights of different design. Methods Comparisons were made using a Servolite LED light, a General Electric (GE) Lullaby and a Ningbo David LED phototherapy light. Measurements were done according to methods described by the International Electrotechnical Communission (IEC). The effective irradiated area was measured on a grid measuring 60 x 30 cm subdivided into 5 x 5 cm squares. Measurements were done for the following scenarios: light placed at the manufacturers' recommended distance, 20 cm closer, 20 cm further, at an angle, through clear plastic and through scuffed perspex. Results When the lights were placed closer to the irradiated surface than the manufacturers' recommendations, the maximum irradiance increased, but the median irradiance and uniformity ratio decreased. When the lights were angled at 45 the median irradiance was decreased. A decrease in the median irradiance was also seen when phototherapy lights passed through scuffed plastic and food grade plastic. Conclusion Our study demonstrated that placing LED lights closer than the manufacturers recommendations, the use of transparent barriers and the use of lights at an angle, compromised phototherapy irradiance and distribution. Only the GE light met IEC standards.