Optical Coherence Tomography for Dermatological Applications

Abstract: Popular Abstract in English Cancer diagnostics is an increasingly important task in the modern world due to an increasing cancer incidence and because diagnostics and treatment are given higher priority. There are many requirements to a diagnostic system. First of all it is important to provide an accurate diagnosis to be able to choose the right treatment. In addition, it is preferable that the method is non-invasive opposite the common used biopsy. Moreover, a relative quick method without any post processing is advantageous. Finally, a relative cheap method is preferable not to prevent widespread use. In general there are no diagnostic systems today fulfilling all criteria mentioned above. Therefore intensive research in new diagnostic systems is performed including optical methods. Optical coherence tomography (OCT) is a non-invasive optical technique providing real time images of tissue with a resolution of about 10 micrometer. The technique is simple and therefore relative low cost commercial systems are potentially realizable. However, it is still an open question whether OCT images can replace biopsies. The scope of this project is to investigate if OCT can contribute to an improved diagnosis of skin diseases, in particular skin cancer. This has been accomplished by performing clinical measurements as well as improvement and tailoring of the technique. In cooperation with medical doctors, the main clinical study involved 100 patients with skin cancer and investigated the potential for diagnostics. This study revealed that technical improvements are needed before OCT might be used. An improved spatial resolution enables visualization of finer details in the images and could be important for the diagnostic value of OCT. The technical part of this project has therefore been focused on improving the resolution to a level enabling single cell visualization. An OCT system supporting imaging with a resolution of about 2 micrometer has been constructed. The system has been tested with preliminary light sources developed in an European collaboration with promising results. Unfortunately, the light sources have not been fully developed and therefore clinical measurements using the system have not been possible. In addition to the diagnostic studies and development of the technique itself, monitoring of treatment has been attempted. Using a Doppler OCT system it is possible to detect the blood flow in the skin. During treatment of skin cancer using photodynamic therapy, measurement of changes in blood flow has been attempted because it is hypothesized that this could be used for determining the treatment effect. Potentially, the blood flow information could be used for tailoring the treatment individually to every patient and eventually improve the outcome. These introductory measurements have identified a number of problems and possible solutions are suggested.