We propose an architecture with a remote phosphor-based modular and compact light-emitting diode (LED) light source in a noncontact dermoscope prototype for skin cancer screening. The spectrum and color temperature of the output light can easily and significantly be changed depending on spectral absorption characteristics of the tissues being imaged. The new system has several advantages compared to state-of-the-art phosphor converted ultrabright white LEDs, used in a wide range of medical imaging devices, which have a fixed spectrum and color temperature at a given operating point. In particular, the system can more easily be adapted to the requirements originating from different tissues in the human body, which have wavelength-dependent absorption and reflectivity. This leads to improved contrast for different kinds of imaged tissue components. The concept of such a lighting architecture can be vastly utilized in many other medical imaging devices including endoscopic systems.
Early detection and excision of melanoma skin cancer is crucial for a successful therapy. Dermoscopy in direct contact
with the skin is routinely used for inspection, but screening is time consuming for high-risk patients with a large number
of nevi. Features like symmetry, border, color and most importantly changes like growth or depigmentation of a nevus
may indicate malignancy. We present a non-contact remote imaging system for human melanocytic nevi with
homogenous illumination by an ultra-bright white LED. The advantage compared to established dermoscopy systems
requiring direct skin contact is that deformation of raised nevi is avoided and full-body scans of the patients may time-efficiently
be obtained while they are in a lying, comfortable position. This will ultimately allow for automated screening
in the future. In addition, calibration of true color rendering, which is essential for distinguishing between benign and
malignant lesions and to ensure reproducibility and comparison between individual check-ups in order to follow nevi
evolution is implemented as well as suppression of specular highlights on the skin surface by integration of polarizing
filters. Important features of the system which will be crucial for future integration into automated systems are the
possibility to record images without artifacts in combination with short exposure times which both reduce image blurring
caused by patient motion.