Abstract
Daylight-mediated photodynamic therapy (daylight PDT) is a simple and pain free treatment of actinic keratoses. Weather conditions may not always allow daylight PDT outdoors. We compared the spectrum of five different lamp candidates for indoor “daylight PDT” and investigated their ability to photobleach protoporphyrin IX (PpIX). Furthermore, we measured the amount of PpIX activating daylight available in a glass greenhouse, which can be an alternative when it is uncomfortable for patients to be outdoors. The lamps investigated were: halogen lamps (overhead and slide projector), white light-emitting diode (LED) lamp, red LED panel and lamps used for conventional PDT. Four of the five light sources were able to photobleach PpIX completely. For halogen light and the red LED lamp, 5000 lux could photobleach PpIX whereas 12,000 lux were needed for the white LED lamp. Furthermore, the greenhouse was suitable for daylight PDT since the effect of solar light is lowered only by 25%. In conclusion, we found four of the five light sources and the greenhouse usable for indoor daylight PDT. The greenhouse is beneficial when the weather outside is rainy or windy. Only insignificant ultraviolet B radiation (UVB) radiation passes through the greenhouse glass, so sun protection is not needed.
Highlights
IntroductionDaylight photodynamic therapy (daylight-PDT) has become an established treatment for actinic keratoses [1]
Daylight photodynamic therapy has become an established treatment for actinic keratoses [1]
We investigated five different commercially available light sources
Summary
Daylight photodynamic therapy (daylight-PDT) has become an established treatment for actinic keratoses [1]. The daylight PDT regimen includes superficial curettage, application of methyl aminolevulinate (MAL) and two hours outdoors in daylight starting 30 min. In Denmark it is only possible to perform daylight-mediated PDT from April to November due to low temperatures and insufficient daylight doses the rest of the year [3,7]. Treatment rooms with artificial “daylight” would enable us to treat patients all year round, on rainy days during summer. In the infancy of PDT, slide projectors were used as a light source before LED technology became available [8,9]. Attempts have been made to develop other artificial daylight illumination systems, but these are not yet commercially available [10]. All PpIX absorption peaks are within the visible spectrum of light (Figure 1) [11]
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