OCT images of human skin

The aim of this research is the investigation and improvement of the possibilities of optical coherence tomography (OCT) for evaluation and imaging of dermal lesions, such as melanoma. Single point detection, as done with fibre arrangements using photomultiplier for measurements on human eyes was not successful in reaching high resolutions in strongly scattering media as human skin. The maximum scanning depth was about 500 mu m. For this reason, a new system with a wide area detection was developed. The experimental set-up consists of a highly sensitive slow-scan CCD-camera and a suitably adapted interferometric arrangement. Measurements were performed on a model made of scattering material with simple objects embedded. They show that images appear to be blurred as a consequence of the wide area detection which allows an increased measuring depth. These investigations lead to a new method for the improvement of the OCT images which is explained and demonstrated on measurements performed on the model. Measurements on preserved specimen of human skin up to a scanning depth of 2 mm are shown in comparison to corresponding histological slides to demonstrate the spatial resolution and the ability of optical coherence methods to distinguish structures with different optical parameters.