Stereoscopic Skin Mapping for Dermatology

Abstract

Dermatological assessment of localization and extent of skin involvement is often a pre-requisite for therapy planning and therapeutic effects evaluation. Topodermatographic Image Analysis systems use only 2D information for mole mapping which does not allow precise 3D measurements. Photogrammetry can reconstruct surfaces in the 3D space from multiple 2D image data. For this purpose, a stereoscopic prototype system was created that uses two or more digital consumer cameras. Structured projected light is used for the stereo reconstruction of the skin surface, and patient-pose invariant light for the actual skin texture. The patient is rotated on a motorized turntable for a full coverage of the trunk. Dense stereo matching results in a point cloud overlaid with texture from the skin. After merging the results of different views a full textured reconstruction of the patient’s trunk is available as digital surface model (DSM) projected on a near-elliptical shape. Visualization is done by triangulation that generates a VRML2.0 file (3D and highresolution texture). The system has been realized as a low-cost solution covering the principle requirements of 3D documentation in dermatology. The hard- and software is described, examples and performance are demonstrated. It is an operational tool for image data management, visualization, measurement on the unwrapped surface, and 3D data export. First reconstructions are shown together with software that allows timeseries comparison in 3D. Data collection and dermatologic exploitation has started begin of 2003. Skin Mapping is a joint development of JOANNEUM RESEARCH, the University of Graz Department of Dermatology and DIBIT Messtechnik GmbH of Mils, Austria.