1. Institute for Electrical Engineering in Medicine , University of Lübeck , Lübeck , Germany
2. Lucas Varity GmbH , Koblenz , Germany . Benedikt Schmarkbeck was with Medizinisches Laserzentrum Lübeck at the time the contents of this article were conceived
3. Medizinisches Laserzentrum Lübeck GmbH , Lübeck , Germany
4. Institute of Biomedical Optics , University of Lübeck , Lübeck , Germany